[v6,4/5] PM / devfreq: Add dynamic scaling for imx8m ddr controller

Commit Message

Leonard Crestez Nov. 14, 2019, 6:33 p.m. UTC

Add driver for dynamic scaling the DDR Controller on imx8m chips. Actual
frequency switching is implemented inside TF-A, this driver wraps the
SMC calls and synchronizes the clk tree.

The DRAM clocks on imx8m have the following structure (abridged):

 +----------+       |\            +------+
 | dram_pll |-------|M| dram_core |      |
 +----------+       |U|---------->| D    |
                 /--|X|           |  D   |
   dram_alt_root |  |/            |   R  |
                 |                |    C |
            +---------+           |      |
            |FIX DIV/4|           |      |
            +---------+           |      |
  composite:     |                |      |
 +----------+    |                |      |
 | dram_alt |----/                |      |
 +----------+                     |      |
 | dram_apb |-------------------->|      |
 +----------+                     +------+

The dram_pll is used for higher rates and dram_alt is used for lower
rates. The dram_alt and dram_apb clocks are "imx composite" and their
parent can also be modified.

This driver will prepare/enable the new parents ahead of switching (so
that the expected roots are enabled) and afterwards it will call
clk_set_parent to ensure the parents in clock framework are up-to-date.

The driver relies on dram_pll dram_alt and dram_apb being marked with
CLK_GET_RATE_NOCACHE for rate updates.

Signed-off-by: Leonard Crestez <[e-mail]>
---
 drivers/devfreq/Kconfig      |   9 +
 drivers/devfreq/Makefile     |   1 +
 drivers/devfreq/imx8m-ddrc.c | 465 +++++++++++++++++++++++++++++++++++
 3 files changed, 475 insertions(+)
 create mode 100644 drivers/devfreq/imx8m-ddrc.c

Comments

Chanwoo Choi Nov. 15, 2019, 1:31 a.m. UTC | #1

Hi Leonard,

Looks good to me.
Acked-by: Chanwoo Choi <[e-mail]>

After reviewing the dt-binding patch from DT maintainer,
I'll take patch3/patch4 to devfreq git. 

Or, Should I have to finish the review of patch1/patch2?

Regards,
Chanwoo Choi

On 11/15/19 3:33 AM, Leonard Crestez wrote:
> Add driver for dynamic scaling the DDR Controller on imx8m chips. Actual
> frequency switching is implemented inside TF-A, this driver wraps the
> SMC calls and synchronizes the clk tree.
> 
> The DRAM clocks on imx8m have the following structure (abridged):
> 
>  +----------+       |\            +------+
>  | dram_pll |-------|M| dram_core |      |
>  +----------+       |U|---------->| D    |
>                  /--|X|           |  D   |
>    dram_alt_root |  |/            |   R  |
>                  |                |    C |
>             +---------+           |      |
>             |FIX DIV/4|           |      |
>             +---------+           |      |
>   composite:     |                |      |
>  +----------+    |                |      |
>  | dram_alt |----/                |      |
>  +----------+                     |      |
>  | dram_apb |-------------------->|      |
>  +----------+                     +------+
> 
> The dram_pll is used for higher rates and dram_alt is used for lower
> rates. The dram_alt and dram_apb clocks are "imx composite" and their
> parent can also be modified.
> 
> This driver will prepare/enable the new parents ahead of switching (so
> that the expected roots are enabled) and afterwards it will call
> clk_set_parent to ensure the parents in clock framework are up-to-date.
> 
> The driver relies on dram_pll dram_alt and dram_apb being marked with
> CLK_GET_RATE_NOCACHE for rate updates.
> 
> Signed-off-by: Leonard Crestez <[e-mail]>
> ---
>  drivers/devfreq/Kconfig      |   9 +
>  drivers/devfreq/Makefile     |   1 +
>  drivers/devfreq/imx8m-ddrc.c | 465 +++++++++++++++++++++++++++++++++++
>  3 files changed, 475 insertions(+)
>  create mode 100644 drivers/devfreq/imx8m-ddrc.c
> 
> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
> index 066e6c4efaa2..923a6132e741 100644
> --- a/drivers/devfreq/Kconfig
> +++ b/drivers/devfreq/Kconfig
> @@ -89,10 +89,19 @@ config ARM_EXYNOS_BUS_DEVFREQ
>  	  Each memory bus group could contain many memoby bus block. It reads
>  	  PPMU counters of memory controllers by using DEVFREQ-event device
>  	  and adjusts the operating frequencies and voltages with OPP support.
>  	  This does not yet operate with optimal voltages.
>  
> +config ARM_IMX8M_DDRC_DEVFREQ
> +	tristate "i.MX8M DDRC DEVFREQ Driver"
> +	depends on ARCH_MXC || COMPILE_TEST
> +	select DEVFREQ_GOV_SIMPLE_ONDEMAND
> +	select DEVFREQ_GOV_USERSPACE
> +	help
> +	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
> +	  adjusting DRAM frequency.
> +
>  config ARM_TEGRA_DEVFREQ
>  	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
>  	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
>  		ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
>  		ARCH_TEGRA_210_SOC || \
> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
> index 338ae8440db6..3eb4d5e6635c 100644
> --- a/drivers/devfreq/Makefile
> +++ b/drivers/devfreq/Makefile
> @@ -7,10 +7,11 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
>  obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>  obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>  
>  # DEVFREQ Drivers
>  obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
> +obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
>  obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>  obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
>  obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
>  
>  # DEVFREQ Event Drivers
> diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-ddrc.c
> new file mode 100644
> index 000000000000..fea169619c59
> --- /dev/null
> +++ b/drivers/devfreq/imx8m-ddrc.c
> @@ -0,0 +1,465 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2019 NXP
> + */
> +
> +#include <linux/module.h>
> +#include <linux/device.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/devfreq.h>
> +#include <linux/pm_opp.h>
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/arm-smccc.h>
> +
> +#define IMX_SIP_DDR_DVFS			0xc2000004
> +
> +/* Values starting from 0 switch to specific frequency */
> +#define IMX_SIP_DDR_FREQ_SET_HIGH		0x00
> +
> +/* Deprecated after moving IRQ handling to ATF */
> +#define IMX_SIP_DDR_DVFS_WAIT_CHANGE		0x0F
> +
> +/* Query available frequencies. */
> +#define IMX_SIP_DDR_DVFS_GET_FREQ_COUNT		0x10
> +#define IMX_SIP_DDR_DVFS_GET_FREQ_INFO		0x11
> +
> +/*
> + * This should be in a 1:1 mapping with devicetree OPPs but
> + * firmware provides additional info.
> + */
> +struct imx8m_ddrc_freq {
> +	unsigned long rate;
> +	unsigned long smcarg;
> +	int dram_core_parent_index;
> +	int dram_alt_parent_index;
> +	int dram_apb_parent_index;
> +};
> +
> +/* Hardware limitation */
> +#define IMX8M_DDRC_MAX_FREQ_COUNT 4
> +
> +/*
> + * i.MX8M DRAM Controller clocks have the following structure (abridged):
> + *
> + * +----------+       |\            +------+
> + * | dram_pll |-------|M| dram_core |      |
> + * +----------+       |U|---------->| D    |
> + *                 /--|X|           |  D   |
> + *   dram_alt_root |  |/            |   R  |
> + *                 |                |    C |
> + *            +---------+           |      |
> + *            |FIX DIV/4|           |      |
> + *            +---------+           |      |
> + *  composite:     |                |      |
> + * +----------+    |                |      |
> + * | dram_alt |----/                |      |
> + * +----------+                     |      |
> + * | dram_apb |-------------------->|      |
> + * +----------+                     +------+
> + *
> + * The dram_pll is used for higher rates and dram_alt is used for lower rates.
> + *
> + * Frequency switching is implemented in TF-A (via SMC call) and can change the
> + * configuration of the clocks, including mux parents. The dram_alt and
> + * dram_apb clocks are "imx composite" and their parent can change too.
> + *
> + * We need to prepare/enable the new mux parents head of switching and update
> + * their information afterwards.
> + */
> +struct imx8m_ddrc {
> +	struct devfreq_dev_profile profile;
> +	struct devfreq *devfreq;
> +
> +	/* For frequency switching: */
> +	struct clk *dram_core;
> +	struct clk *dram_pll;
> +	struct clk *dram_alt;
> +	struct clk *dram_apb;
> +
> +	int freq_count;
> +	struct imx8m_ddrc_freq freq_table[IMX8M_DDRC_MAX_FREQ_COUNT];
> +};
> +
> +static struct imx8m_ddrc_freq *imx8m_ddrc_find_freq(struct imx8m_ddrc *priv,
> +						    unsigned long rate)
> +{
> +	struct imx8m_ddrc_freq *freq;
> +	int i;
> +
> +	/*
> +	 * Firmware reports values in MT/s, so we round-down from Hz
> +	 * Rounding is extra generous to ensure a match.
> +	 */
> +	rate = DIV_ROUND_CLOSEST(rate, 250000);
> +	for (i = 0; i < priv->freq_count; ++i) {
> +		freq = &priv->freq_table[i];
> +		if (freq->rate == rate ||
> +				freq->rate + 1 == rate ||
> +				freq->rate - 1 == rate)
> +			return freq;
> +	}
> +
> +	return NULL;
> +}
> +
> +static void imx8m_ddrc_smc_set_freq(int target_freq)
> +{
> +	struct arm_smccc_res res;
> +	u32 online_cpus = 0;
> +	int cpu;
> +
> +	local_irq_disable();
> +
> +	for_each_online_cpu(cpu)
> +		online_cpus |= (1 << (cpu * 8));
> +
> +	/* change the ddr freqency */
> +	arm_smccc_smc(IMX_SIP_DDR_DVFS, target_freq, online_cpus,
> +			0, 0, 0, 0, 0, &res);
> +
> +	local_irq_enable();
> +}
> +
> +static struct clk *clk_get_parent_by_index(struct clk *clk, int index)
> +{
> +	struct clk_hw *hw;
> +
> +	hw = clk_hw_get_parent_by_index(__clk_get_hw(clk), index);
> +
> +	return hw ? hw->clk : NULL;
> +}
> +
> +static int imx8m_ddrc_set_freq(struct device *dev, struct imx8m_ddrc_freq *freq)
> +{
> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> +	struct clk *new_dram_core_parent;
> +	struct clk *new_dram_alt_parent;
> +	struct clk *new_dram_apb_parent;
> +	int ret;
> +
> +	/*
> +	 * Fetch new parents
> +	 *
> +	 * new_dram_alt_parent and new_dram_apb_parent are optional but
> +	 * new_dram_core_parent is not.
> +	 */
> +	new_dram_core_parent = clk_get_parent_by_index(
> +			priv->dram_core, freq->dram_core_parent_index - 1);
> +	if (!new_dram_core_parent) {
> +		dev_err(dev, "failed to fetch new dram_core parent\n");
> +		return -EINVAL;
> +	}
> +	if (freq->dram_alt_parent_index) {
> +		new_dram_alt_parent = clk_get_parent_by_index(
> +				priv->dram_alt,
> +				freq->dram_alt_parent_index - 1);
> +		if (!new_dram_alt_parent) {
> +			dev_err(dev, "failed to fetch new dram_alt parent\n");
> +			return -EINVAL;
> +		}
> +	} else
> +		new_dram_alt_parent = NULL;
> +
> +	if (freq->dram_apb_parent_index) {
> +		new_dram_apb_parent = clk_get_parent_by_index(
> +				priv->dram_apb,
> +				freq->dram_apb_parent_index - 1);
> +		if (!new_dram_apb_parent) {
> +			dev_err(dev, "failed to fetch new dram_apb parent\n");
> +			return -EINVAL;
> +		}
> +	} else
> +		new_dram_apb_parent = NULL;
> +
> +	/* increase reference counts and ensure clks are ON before switch */
> +	ret = clk_prepare_enable(new_dram_core_parent);
> +	if (ret) {
> +		dev_err(dev, "failed to enable new dram_core parent: %d\n",
> +			ret);
> +		goto out;
> +	}
> +	ret = clk_prepare_enable(new_dram_alt_parent);
> +	if (ret) {
> +		dev_err(dev, "failed to enable new dram_alt parent: %d\n",
> +			ret);
> +		goto out_disable_core_parent;
> +	}
> +	ret = clk_prepare_enable(new_dram_apb_parent);
> +	if (ret) {
> +		dev_err(dev, "failed to enable new dram_apb parent: %d\n",
> +			ret);
> +		goto out_disable_alt_parent;
> +	}
> +
> +	imx8m_ddrc_smc_set_freq(freq->smcarg);
> +
> +	/* update parents in clk tree after switch. */
> +	ret = clk_set_parent(priv->dram_core, new_dram_core_parent);
> +	if (ret)
> +		dev_warn(dev, "failed to set dram_core parent: %d\n", ret);
> +	if (new_dram_alt_parent) {
> +		ret = clk_set_parent(priv->dram_alt, new_dram_alt_parent);
> +		if (ret)
> +			dev_warn(dev, "failed to set dram_alt parent: %d\n",
> +				 ret);
> +	}
> +	if (new_dram_apb_parent) {
> +		ret = clk_set_parent(priv->dram_apb, new_dram_apb_parent);
> +		if (ret)
> +			dev_warn(dev, "failed to set dram_apb parent: %d\n",
> +				 ret);
> +	}
> +
> +	/*
> +	 * Explicitly refresh dram PLL rate.
> +	 *
> +	 * Even if it's marked with CLK_GET_RATE_NOCACHE the rate will not be
> +	 * automatically refreshed when clk_get_rate is called on children.
> +	 */
> +	clk_get_rate(priv->dram_pll);
> +
> +	/*
> +	 * clk_set_parent transfer the reference count from old parent.
> +	 * now we drop extra reference counts used during the switch
> +	 */
> +	clk_disable_unprepare(new_dram_apb_parent);
> +out_disable_alt_parent:
> +	clk_disable_unprepare(new_dram_alt_parent);
> +out_disable_core_parent:
> +	clk_disable_unprepare(new_dram_core_parent);
> +out:
> +	return ret;
> +}
> +
> +static int imx8m_ddrc_target(struct device *dev, unsigned long *freq, u32 flags)
> +{
> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> +	struct imx8m_ddrc_freq *freq_info;
> +	struct dev_pm_opp *new_opp;
> +	unsigned long old_freq, new_freq;
> +	int ret;
> +
> +	new_opp = devfreq_recommended_opp(dev, freq, flags);
> +	if (IS_ERR(new_opp)) {
> +		ret = PTR_ERR(new_opp);
> +		dev_err(dev, "failed to get recommended opp: %d\n", ret);
> +		return ret;
> +	}
> +	dev_pm_opp_put(new_opp);
> +
> +	old_freq = clk_get_rate(priv->dram_core);
> +	if (*freq == old_freq)
> +		return 0;
> +
> +	freq_info = imx8m_ddrc_find_freq(priv, *freq);
> +	if (!freq_info)
> +		return -EINVAL;
> +
> +	/*
> +	 * Read back the clk rate to verify switch was correct and so that
> +	 * we can report it on all error paths.
> +	 */
> +	ret = imx8m_ddrc_set_freq(dev, freq_info);
> +
> +	new_freq = clk_get_rate(priv->dram_core);
> +	if (ret)
> +		dev_err(dev, "ddrc failed freq switch to %lu from %lu: error %d. now at %lu\n",
> +			old_freq, *freq, ret, new_freq);
> +	else if (*freq != new_freq)
> +		dev_err(dev, "ddrc failed freq update to %lu from %lu, now at %lu\n",
> +			old_freq, *freq, new_freq);
> +	else
> +		dev_dbg(dev, "ddrc freq set to %lu (was %lu)\n",
> +			*freq, old_freq);
> +
> +	return ret;
> +}
> +
> +static int imx8m_ddrc_get_cur_freq(struct device *dev, unsigned long *freq)
> +{
> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> +
> +	*freq = clk_get_rate(priv->dram_core);
> +
> +	return 0;
> +}
> +
> +static int imx8m_ddrc_get_dev_status(struct device *dev,
> +				     struct devfreq_dev_status *stat)
> +{
> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> +
> +	stat->busy_time = 0;
> +	stat->total_time = 0;
> +	stat->current_frequency = clk_get_rate(priv->dram_core);
> +
> +	return 0;
> +}
> +
> +static int imx8m_ddrc_init_freq_info(struct device *dev)
> +{
> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> +	struct arm_smccc_res res;
> +	int index;
> +
> +	/* An error here means DDR DVFS API not supported by firmware */
> +	arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_COUNT,
> +			0, 0, 0, 0, 0, 0, &res);
> +	priv->freq_count = res.a0;
> +	if (priv->freq_count <= 0 ||
> +			priv->freq_count > IMX8M_DDRC_MAX_FREQ_COUNT)
> +		return -ENODEV;
> +
> +	for (index = 0; index < priv->freq_count; ++index) {
> +		struct imx8m_ddrc_freq *freq = &priv->freq_table[index];
> +
> +		arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_INFO,
> +			      index, 0, 0, 0, 0, 0, &res);
> +		/* Result should be strictly positive */
> +		if ((long)res.a0 <= 0)
> +			return -ENODEV;
> +
> +		freq->rate = res.a0;
> +		freq->smcarg = index;
> +		freq->dram_core_parent_index = res.a1;
> +		freq->dram_alt_parent_index = res.a2;
> +		freq->dram_apb_parent_index = res.a3;
> +
> +		/* dram_core has 2 options: dram_pll or dram_alt_root */
> +		if (freq->dram_core_parent_index != 1 &&
> +				freq->dram_core_parent_index != 2)
> +			return -ENODEV;
> +		/* dram_apb and dram_alt have exactly 8 possible parents */
> +		if (freq->dram_alt_parent_index > 8 ||
> +				freq->dram_apb_parent_index > 8)
> +			return -ENODEV;
> +		/* dram_core from alt requires explicit dram_alt parent */
> +		if (freq->dram_core_parent_index == 2 &&
> +				freq->dram_alt_parent_index == 0)
> +			return -ENODEV;
> +	}
> +
> +	return 0;
> +}
> +
> +static int imx8m_ddrc_check_opps(struct device *dev)
> +{
> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
> +	struct imx8m_ddrc_freq *freq_info;
> +	struct dev_pm_opp *opp;
> +	unsigned long freq;
> +	int i, opp_count;
> +
> +	/* Enumerate DT OPPs and disable those not supported by firmware */
> +	opp_count = dev_pm_opp_get_opp_count(dev);
> +	if (opp_count < 0)
> +		return opp_count;
> +	for (i = 0, freq = 0; i < opp_count; ++i, ++freq) {
> +		opp = dev_pm_opp_find_freq_ceil(dev, &freq);
> +		if (IS_ERR(opp)) {
> +			dev_err(dev, "Failed enumerating OPPs: %ld\n",
> +				PTR_ERR(opp));
> +			return PTR_ERR(opp);
> +		}
> +		dev_pm_opp_put(opp);
> +
> +		freq_info = imx8m_ddrc_find_freq(priv, freq);
> +		if (!freq_info) {
> +			dev_info(dev, "Disable unsupported OPP %luHz %luMT/s\n",
> +					freq, DIV_ROUND_CLOSEST(freq, 250000));
> +			dev_pm_opp_disable(dev, freq);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void imx8m_ddrc_exit(struct device *dev)
> +{
> +	dev_pm_opp_of_remove_table(dev);
> +}
> +
> +static int imx8m_ddrc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct imx8m_ddrc *priv;
> +	const char *gov = DEVFREQ_GOV_USERSPACE;
> +	int ret;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, priv);
> +
> +	ret = imx8m_ddrc_init_freq_info(dev);
> +	if (ret) {
> +		dev_err(dev, "failed to init firmware freq info: %d\n", ret);
> +		return ret;
> +	}
> +
> +	priv->dram_core = devm_clk_get(dev, "core");
> +	priv->dram_pll = devm_clk_get(dev, "pll");
> +	priv->dram_alt = devm_clk_get(dev, "alt");
> +	priv->dram_apb = devm_clk_get(dev, "apb");
> +	if (IS_ERR(priv->dram_core) ||
> +		IS_ERR(priv->dram_pll) ||
> +		IS_ERR(priv->dram_alt) ||
> +		IS_ERR(priv->dram_apb)) {
> +		ret = PTR_ERR(priv->devfreq);
> +		dev_err(dev, "failed to fetch clocks: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = dev_pm_opp_of_add_table(dev);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to get OPP table\n");
> +		return ret;
> +	}
> +
> +	ret = imx8m_ddrc_check_opps(dev);
> +	if (ret < 0)
> +		goto err;
> +
> +	priv->profile.polling_ms = 1000;
> +	priv->profile.target = imx8m_ddrc_target;
> +	priv->profile.get_dev_status = imx8m_ddrc_get_dev_status;
> +	priv->profile.exit = imx8m_ddrc_exit;
> +	priv->profile.get_cur_freq = imx8m_ddrc_get_cur_freq;
> +	priv->profile.initial_freq = clk_get_rate(priv->dram_core);
> +
> +	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
> +						gov, NULL);
> +	if (IS_ERR(priv->devfreq)) {
> +		ret = PTR_ERR(priv->devfreq);
> +		dev_err(dev, "failed to add devfreq device: %d\n", ret);
> +		goto err;
> +	}
> +
> +	return 0;
> +
> +err:
> +	dev_pm_opp_of_remove_table(dev);
> +	return ret;
> +}
> +
> +static const struct of_device_id imx8m_ddrc_of_match[] = {
> +	{ .compatible = "fsl,imx8m-ddrc", },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, imx8m_ddrc_of_match);
> +
> +static struct platform_driver imx8m_ddrc_platdrv = {
> +	.probe		= imx8m_ddrc_probe,
> +	.driver = {
> +		.name	= "imx8m-ddrc-devfreq",
> +		.of_match_table = of_match_ptr(imx8m_ddrc_of_match),
> +	},
> +};
> +module_platform_driver(imx8m_ddrc_platdrv);
> +
> +MODULE_DESCRIPTION("i.MX8M DDR Controller frequency driver");
> +MODULE_AUTHOR("Leonard Crestez <[e-mail]>");
> +MODULE_LICENSE("GPL v2");
>

Leonard Crestez Nov. 18, 2019, 2:37 p.m. UTC | #2

On 2019-11-15 3:26 AM, Chanwoo Choi wrote:
> After reviewing the dt-binding patch from DT maintainer,
> I'll take patch3/patch4 to devfreq git.
> 
> Or, Should I have to finish the review of patch1/patch2?
Patches 1/2 were already reviewed but they conflict with other pending 
series doing clk_hw cleanups:

     https://patchwork.kernel.org/cover/11224933/
     https://patchwork.kernel.org/cover/11217881/

Those cleanups would conflict with most imx8m clk changes, it might make 
sense to wait for them to enter first and then I'll send a v7 of devfreq 
with solved conflicts and collected acks.

Shawn / Stephen: How should we proceed?

> Regards,
> Chanwoo Choi
> 
> On 11/15/19 3:33 AM, Leonard Crestez wrote:
>> Add driver for dynamic scaling the DDR Controller on imx8m chips. Actual
>> frequency switching is implemented inside TF-A, this driver wraps the
>> SMC calls and synchronizes the clk tree.
>>
>> The DRAM clocks on imx8m have the following structure (abridged):
>>
>>   +----------+       |\            +------+
>>   | dram_pll |-------|M| dram_core |      |
>>   +----------+       |U|---------->| D    |
>>                   /--|X|           |  D   |
>>     dram_alt_root |  |/            |   R  |
>>                   |                |    C |
>>              +---------+           |      |
>>              |FIX DIV/4|           |      |
>>              +---------+           |      |
>>    composite:     |                |      |
>>   +----------+    |                |      |
>>   | dram_alt |----/                |      |
>>   +----------+                     |      |
>>   | dram_apb |-------------------->|      |
>>   +----------+                     +------+
>>
>> The dram_pll is used for higher rates and dram_alt is used for lower
>> rates. The dram_alt and dram_apb clocks are "imx composite" and their
>> parent can also be modified.
>>
>> This driver will prepare/enable the new parents ahead of switching (so
>> that the expected roots are enabled) and afterwards it will call
>> clk_set_parent to ensure the parents in clock framework are up-to-date.
>>
>> The driver relies on dram_pll dram_alt and dram_apb being marked with
>> CLK_GET_RATE_NOCACHE for rate updates.
>>
>> Signed-off-by: Leonard Crestez <[e-mail]>
>> ---
>>   drivers/devfreq/Kconfig      |   9 +
>>   drivers/devfreq/Makefile     |   1 +
>>   drivers/devfreq/imx8m-ddrc.c | 465 +++++++++++++++++++++++++++++++++++
>>   3 files changed, 475 insertions(+)
>>   create mode 100644 drivers/devfreq/imx8m-ddrc.c
>>
>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>> index 066e6c4efaa2..923a6132e741 100644
>> --- a/drivers/devfreq/Kconfig
>> +++ b/drivers/devfreq/Kconfig
>> @@ -89,10 +89,19 @@ config ARM_EXYNOS_BUS_DEVFREQ
>>   	  Each memory bus group could contain many memoby bus block. It reads
>>   	  PPMU counters of memory controllers by using DEVFREQ-event device
>>   	  and adjusts the operating frequencies and voltages with OPP support.
>>   	  This does not yet operate with optimal voltages.
>>   
>> +config ARM_IMX8M_DDRC_DEVFREQ
>> +	tristate "i.MX8M DDRC DEVFREQ Driver"
>> +	depends on ARCH_MXC || COMPILE_TEST
>> +	select DEVFREQ_GOV_SIMPLE_ONDEMAND
>> +	select DEVFREQ_GOV_USERSPACE
>> +	help
>> +	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
>> +	  adjusting DRAM frequency.
>> +
>>   config ARM_TEGRA_DEVFREQ
>>   	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
>>   	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
>>   		ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
>>   		ARCH_TEGRA_210_SOC || \
>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>> index 338ae8440db6..3eb4d5e6635c 100644
>> --- a/drivers/devfreq/Makefile
>> +++ b/drivers/devfreq/Makefile
>> @@ -7,10 +7,11 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
>>   obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>>   obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>>   
>>   # DEVFREQ Drivers
>>   obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>> +obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
>>   obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>>   obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
>>   obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
>>   
>>   # DEVFREQ Event Drivers
>> diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-ddrc.c
>> new file mode 100644
>> index 000000000000..fea169619c59
>> --- /dev/null
>> +++ b/drivers/devfreq/imx8m-ddrc.c
>> @@ -0,0 +1,465 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright 2019 NXP
>> + */
>> +
>> +#include <linux/module.h>
>> +#include <linux/device.h>
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/devfreq.h>
>> +#include <linux/pm_opp.h>
>> +#include <linux/clk.h>
>> +#include <linux/clk-provider.h>
>> +#include <linux/arm-smccc.h>
>> +
>> +#define IMX_SIP_DDR_DVFS			0xc2000004
>> +
>> +/* Values starting from 0 switch to specific frequency */
>> +#define IMX_SIP_DDR_FREQ_SET_HIGH		0x00
>> +
>> +/* Deprecated after moving IRQ handling to ATF */
>> +#define IMX_SIP_DDR_DVFS_WAIT_CHANGE		0x0F
>> +
>> +/* Query available frequencies. */
>> +#define IMX_SIP_DDR_DVFS_GET_FREQ_COUNT		0x10
>> +#define IMX_SIP_DDR_DVFS_GET_FREQ_INFO		0x11
>> +
>> +/*
>> + * This should be in a 1:1 mapping with devicetree OPPs but
>> + * firmware provides additional info.
>> + */
>> +struct imx8m_ddrc_freq {
>> +	unsigned long rate;
>> +	unsigned long smcarg;
>> +	int dram_core_parent_index;
>> +	int dram_alt_parent_index;
>> +	int dram_apb_parent_index;
>> +};
>> +
>> +/* Hardware limitation */
>> +#define IMX8M_DDRC_MAX_FREQ_COUNT 4
>> +
>> +/*
>> + * i.MX8M DRAM Controller clocks have the following structure (abridged):
>> + *
>> + * +----------+       |\            +------+
>> + * | dram_pll |-------|M| dram_core |      |
>> + * +----------+       |U|---------->| D    |
>> + *                 /--|X|           |  D   |
>> + *   dram_alt_root |  |/            |   R  |
>> + *                 |                |    C |
>> + *            +---------+           |      |
>> + *            |FIX DIV/4|           |      |
>> + *            +---------+           |      |
>> + *  composite:     |                |      |
>> + * +----------+    |                |      |
>> + * | dram_alt |----/                |      |
>> + * +----------+                     |      |
>> + * | dram_apb |-------------------->|      |
>> + * +----------+                     +------+
>> + *
>> + * The dram_pll is used for higher rates and dram_alt is used for lower rates.
>> + *
>> + * Frequency switching is implemented in TF-A (via SMC call) and can change the
>> + * configuration of the clocks, including mux parents. The dram_alt and
>> + * dram_apb clocks are "imx composite" and their parent can change too.
>> + *
>> + * We need to prepare/enable the new mux parents head of switching and update
>> + * their information afterwards.
>> + */
>> +struct imx8m_ddrc {
>> +	struct devfreq_dev_profile profile;
>> +	struct devfreq *devfreq;
>> +
>> +	/* For frequency switching: */
>> +	struct clk *dram_core;
>> +	struct clk *dram_pll;
>> +	struct clk *dram_alt;
>> +	struct clk *dram_apb;
>> +
>> +	int freq_count;
>> +	struct imx8m_ddrc_freq freq_table[IMX8M_DDRC_MAX_FREQ_COUNT];
>> +};
>> +
>> +static struct imx8m_ddrc_freq *imx8m_ddrc_find_freq(struct imx8m_ddrc *priv,
>> +						    unsigned long rate)
>> +{
>> +	struct imx8m_ddrc_freq *freq;
>> +	int i;
>> +
>> +	/*
>> +	 * Firmware reports values in MT/s, so we round-down from Hz
>> +	 * Rounding is extra generous to ensure a match.
>> +	 */
>> +	rate = DIV_ROUND_CLOSEST(rate, 250000);
>> +	for (i = 0; i < priv->freq_count; ++i) {
>> +		freq = &priv->freq_table[i];
>> +		if (freq->rate == rate ||
>> +				freq->rate + 1 == rate ||
>> +				freq->rate - 1 == rate)
>> +			return freq;
>> +	}
>> +
>> +	return NULL;
>> +}
>> +
>> +static void imx8m_ddrc_smc_set_freq(int target_freq)
>> +{
>> +	struct arm_smccc_res res;
>> +	u32 online_cpus = 0;
>> +	int cpu;
>> +
>> +	local_irq_disable();
>> +
>> +	for_each_online_cpu(cpu)
>> +		online_cpus |= (1 << (cpu * 8));
>> +
>> +	/* change the ddr freqency */
>> +	arm_smccc_smc(IMX_SIP_DDR_DVFS, target_freq, online_cpus,
>> +			0, 0, 0, 0, 0, &res);
>> +
>> +	local_irq_enable();
>> +}
>> +
>> +static struct clk *clk_get_parent_by_index(struct clk *clk, int index)
>> +{
>> +	struct clk_hw *hw;
>> +
>> +	hw = clk_hw_get_parent_by_index(__clk_get_hw(clk), index);
>> +
>> +	return hw ? hw->clk : NULL;
>> +}
>> +
>> +static int imx8m_ddrc_set_freq(struct device *dev, struct imx8m_ddrc_freq *freq)
>> +{
>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +	struct clk *new_dram_core_parent;
>> +	struct clk *new_dram_alt_parent;
>> +	struct clk *new_dram_apb_parent;
>> +	int ret;
>> +
>> +	/*
>> +	 * Fetch new parents
>> +	 *
>> +	 * new_dram_alt_parent and new_dram_apb_parent are optional but
>> +	 * new_dram_core_parent is not.
>> +	 */
>> +	new_dram_core_parent = clk_get_parent_by_index(
>> +			priv->dram_core, freq->dram_core_parent_index - 1);
>> +	if (!new_dram_core_parent) {
>> +		dev_err(dev, "failed to fetch new dram_core parent\n");
>> +		return -EINVAL;
>> +	}
>> +	if (freq->dram_alt_parent_index) {
>> +		new_dram_alt_parent = clk_get_parent_by_index(
>> +				priv->dram_alt,
>> +				freq->dram_alt_parent_index - 1);
>> +		if (!new_dram_alt_parent) {
>> +			dev_err(dev, "failed to fetch new dram_alt parent\n");
>> +			return -EINVAL;
>> +		}
>> +	} else
>> +		new_dram_alt_parent = NULL;
>> +
>> +	if (freq->dram_apb_parent_index) {
>> +		new_dram_apb_parent = clk_get_parent_by_index(
>> +				priv->dram_apb,
>> +				freq->dram_apb_parent_index - 1);
>> +		if (!new_dram_apb_parent) {
>> +			dev_err(dev, "failed to fetch new dram_apb parent\n");
>> +			return -EINVAL;
>> +		}
>> +	} else
>> +		new_dram_apb_parent = NULL;
>> +
>> +	/* increase reference counts and ensure clks are ON before switch */
>> +	ret = clk_prepare_enable(new_dram_core_parent);
>> +	if (ret) {
>> +		dev_err(dev, "failed to enable new dram_core parent: %d\n",
>> +			ret);
>> +		goto out;
>> +	}
>> +	ret = clk_prepare_enable(new_dram_alt_parent);
>> +	if (ret) {
>> +		dev_err(dev, "failed to enable new dram_alt parent: %d\n",
>> +			ret);
>> +		goto out_disable_core_parent;
>> +	}
>> +	ret = clk_prepare_enable(new_dram_apb_parent);
>> +	if (ret) {
>> +		dev_err(dev, "failed to enable new dram_apb parent: %d\n",
>> +			ret);
>> +		goto out_disable_alt_parent;
>> +	}
>> +
>> +	imx8m_ddrc_smc_set_freq(freq->smcarg);
>> +
>> +	/* update parents in clk tree after switch. */
>> +	ret = clk_set_parent(priv->dram_core, new_dram_core_parent);
>> +	if (ret)
>> +		dev_warn(dev, "failed to set dram_core parent: %d\n", ret);
>> +	if (new_dram_alt_parent) {
>> +		ret = clk_set_parent(priv->dram_alt, new_dram_alt_parent);
>> +		if (ret)
>> +			dev_warn(dev, "failed to set dram_alt parent: %d\n",
>> +				 ret);
>> +	}
>> +	if (new_dram_apb_parent) {
>> +		ret = clk_set_parent(priv->dram_apb, new_dram_apb_parent);
>> +		if (ret)
>> +			dev_warn(dev, "failed to set dram_apb parent: %d\n",
>> +				 ret);
>> +	}
>> +
>> +	/*
>> +	 * Explicitly refresh dram PLL rate.
>> +	 *
>> +	 * Even if it's marked with CLK_GET_RATE_NOCACHE the rate will not be
>> +	 * automatically refreshed when clk_get_rate is called on children.
>> +	 */
>> +	clk_get_rate(priv->dram_pll);
>> +
>> +	/*
>> +	 * clk_set_parent transfer the reference count from old parent.
>> +	 * now we drop extra reference counts used during the switch
>> +	 */
>> +	clk_disable_unprepare(new_dram_apb_parent);
>> +out_disable_alt_parent:
>> +	clk_disable_unprepare(new_dram_alt_parent);
>> +out_disable_core_parent:
>> +	clk_disable_unprepare(new_dram_core_parent);
>> +out:
>> +	return ret;
>> +}
>> +
>> +static int imx8m_ddrc_target(struct device *dev, unsigned long *freq, u32 flags)
>> +{
>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +	struct imx8m_ddrc_freq *freq_info;
>> +	struct dev_pm_opp *new_opp;
>> +	unsigned long old_freq, new_freq;
>> +	int ret;
>> +
>> +	new_opp = devfreq_recommended_opp(dev, freq, flags);
>> +	if (IS_ERR(new_opp)) {
>> +		ret = PTR_ERR(new_opp);
>> +		dev_err(dev, "failed to get recommended opp: %d\n", ret);
>> +		return ret;
>> +	}
>> +	dev_pm_opp_put(new_opp);
>> +
>> +	old_freq = clk_get_rate(priv->dram_core);
>> +	if (*freq == old_freq)
>> +		return 0;
>> +
>> +	freq_info = imx8m_ddrc_find_freq(priv, *freq);
>> +	if (!freq_info)
>> +		return -EINVAL;
>> +
>> +	/*
>> +	 * Read back the clk rate to verify switch was correct and so that
>> +	 * we can report it on all error paths.
>> +	 */
>> +	ret = imx8m_ddrc_set_freq(dev, freq_info);
>> +
>> +	new_freq = clk_get_rate(priv->dram_core);
>> +	if (ret)
>> +		dev_err(dev, "ddrc failed freq switch to %lu from %lu: error %d. now at %lu\n",
>> +			old_freq, *freq, ret, new_freq);
>> +	else if (*freq != new_freq)
>> +		dev_err(dev, "ddrc failed freq update to %lu from %lu, now at %lu\n",
>> +			old_freq, *freq, new_freq);
>> +	else
>> +		dev_dbg(dev, "ddrc freq set to %lu (was %lu)\n",
>> +			*freq, old_freq);
>> +
>> +	return ret;
>> +}
>> +
>> +static int imx8m_ddrc_get_cur_freq(struct device *dev, unsigned long *freq)
>> +{
>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +
>> +	*freq = clk_get_rate(priv->dram_core);
>> +
>> +	return 0;
>> +}
>> +
>> +static int imx8m_ddrc_get_dev_status(struct device *dev,
>> +				     struct devfreq_dev_status *stat)
>> +{
>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +
>> +	stat->busy_time = 0;
>> +	stat->total_time = 0;
>> +	stat->current_frequency = clk_get_rate(priv->dram_core);
>> +
>> +	return 0;
>> +}
>> +
>> +static int imx8m_ddrc_init_freq_info(struct device *dev)
>> +{
>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +	struct arm_smccc_res res;
>> +	int index;
>> +
>> +	/* An error here means DDR DVFS API not supported by firmware */
>> +	arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_COUNT,
>> +			0, 0, 0, 0, 0, 0, &res);
>> +	priv->freq_count = res.a0;
>> +	if (priv->freq_count <= 0 ||
>> +			priv->freq_count > IMX8M_DDRC_MAX_FREQ_COUNT)
>> +		return -ENODEV;
>> +
>> +	for (index = 0; index < priv->freq_count; ++index) {
>> +		struct imx8m_ddrc_freq *freq = &priv->freq_table[index];
>> +
>> +		arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_INFO,
>> +			      index, 0, 0, 0, 0, 0, &res);
>> +		/* Result should be strictly positive */
>> +		if ((long)res.a0 <= 0)
>> +			return -ENODEV;
>> +
>> +		freq->rate = res.a0;
>> +		freq->smcarg = index;
>> +		freq->dram_core_parent_index = res.a1;
>> +		freq->dram_alt_parent_index = res.a2;
>> +		freq->dram_apb_parent_index = res.a3;
>> +
>> +		/* dram_core has 2 options: dram_pll or dram_alt_root */
>> +		if (freq->dram_core_parent_index != 1 &&
>> +				freq->dram_core_parent_index != 2)
>> +			return -ENODEV;
>> +		/* dram_apb and dram_alt have exactly 8 possible parents */
>> +		if (freq->dram_alt_parent_index > 8 ||
>> +				freq->dram_apb_parent_index > 8)
>> +			return -ENODEV;
>> +		/* dram_core from alt requires explicit dram_alt parent */
>> +		if (freq->dram_core_parent_index == 2 &&
>> +				freq->dram_alt_parent_index == 0)
>> +			return -ENODEV;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static int imx8m_ddrc_check_opps(struct device *dev)
>> +{
>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>> +	struct imx8m_ddrc_freq *freq_info;
>> +	struct dev_pm_opp *opp;
>> +	unsigned long freq;
>> +	int i, opp_count;
>> +
>> +	/* Enumerate DT OPPs and disable those not supported by firmware */
>> +	opp_count = dev_pm_opp_get_opp_count(dev);
>> +	if (opp_count < 0)
>> +		return opp_count;
>> +	for (i = 0, freq = 0; i < opp_count; ++i, ++freq) {
>> +		opp = dev_pm_opp_find_freq_ceil(dev, &freq);
>> +		if (IS_ERR(opp)) {
>> +			dev_err(dev, "Failed enumerating OPPs: %ld\n",
>> +				PTR_ERR(opp));
>> +			return PTR_ERR(opp);
>> +		}
>> +		dev_pm_opp_put(opp);
>> +
>> +		freq_info = imx8m_ddrc_find_freq(priv, freq);
>> +		if (!freq_info) {
>> +			dev_info(dev, "Disable unsupported OPP %luHz %luMT/s\n",
>> +					freq, DIV_ROUND_CLOSEST(freq, 250000));
>> +			dev_pm_opp_disable(dev, freq);
>> +		}
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +static void imx8m_ddrc_exit(struct device *dev)
>> +{
>> +	dev_pm_opp_of_remove_table(dev);
>> +}
>> +
>> +static int imx8m_ddrc_probe(struct platform_device *pdev)
>> +{
>> +	struct device *dev = &pdev->dev;
>> +	struct imx8m_ddrc *priv;
>> +	const char *gov = DEVFREQ_GOV_USERSPACE;
>> +	int ret;
>> +
>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +	if (!priv)
>> +		return -ENOMEM;
>> +
>> +	platform_set_drvdata(pdev, priv);
>> +
>> +	ret = imx8m_ddrc_init_freq_info(dev);
>> +	if (ret) {
>> +		dev_err(dev, "failed to init firmware freq info: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	priv->dram_core = devm_clk_get(dev, "core");
>> +	priv->dram_pll = devm_clk_get(dev, "pll");
>> +	priv->dram_alt = devm_clk_get(dev, "alt");
>> +	priv->dram_apb = devm_clk_get(dev, "apb");
>> +	if (IS_ERR(priv->dram_core) ||
>> +		IS_ERR(priv->dram_pll) ||
>> +		IS_ERR(priv->dram_alt) ||
>> +		IS_ERR(priv->dram_apb)) {
>> +		ret = PTR_ERR(priv->devfreq);
>> +		dev_err(dev, "failed to fetch clocks: %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	ret = dev_pm_opp_of_add_table(dev);
>> +	if (ret < 0) {
>> +		dev_err(dev, "failed to get OPP table\n");
>> +		return ret;
>> +	}
>> +
>> +	ret = imx8m_ddrc_check_opps(dev);
>> +	if (ret < 0)
>> +		goto err;
>> +
>> +	priv->profile.polling_ms = 1000;
>> +	priv->profile.target = imx8m_ddrc_target;
>> +	priv->profile.get_dev_status = imx8m_ddrc_get_dev_status;
>> +	priv->profile.exit = imx8m_ddrc_exit;
>> +	priv->profile.get_cur_freq = imx8m_ddrc_get_cur_freq;
>> +	priv->profile.initial_freq = clk_get_rate(priv->dram_core);
>> +
>> +	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
>> +						gov, NULL);
>> +	if (IS_ERR(priv->devfreq)) {
>> +		ret = PTR_ERR(priv->devfreq);
>> +		dev_err(dev, "failed to add devfreq device: %d\n", ret);
>> +		goto err;
>> +	}
>> +
>> +	return 0;
>> +
>> +err:
>> +	dev_pm_opp_of_remove_table(dev);
>> +	return ret;
>> +}
>> +
>> +static const struct of_device_id imx8m_ddrc_of_match[] = {
>> +	{ .compatible = "fsl,imx8m-ddrc", },
>> +	{ /* sentinel */ },
>> +};
>> +MODULE_DEVICE_TABLE(of, imx8m_ddrc_of_match);
>> +
>> +static struct platform_driver imx8m_ddrc_platdrv = {
>> +	.probe		= imx8m_ddrc_probe,
>> +	.driver = {
>> +		.name	= "imx8m-ddrc-devfreq",
>> +		.of_match_table = of_match_ptr(imx8m_ddrc_of_match),
>> +	},
>> +};
>> +module_platform_driver(imx8m_ddrc_platdrv);
>> +
>> +MODULE_DESCRIPTION("i.MX8M DDR Controller frequency driver");
>> +MODULE_AUTHOR("Leonard Crestez <[e-mail]>");
>> +MODULE_LICENSE("GPL v2");
>>
>

Chanwoo Choi Nov. 22, 2019, 1:47 a.m. UTC | #3

Hi Leonard,

On 11/18/19 11:37 PM, Leonard Crestez wrote:
> On 2019-11-15 3:26 AM, Chanwoo Choi wrote:
>> After reviewing the dt-binding patch from DT maintainer,
>> I'll take patch3/patch4 to devfreq git.
>>
>> Or, Should I have to finish the review of patch1/patch2?
> Patches 1/2 were already reviewed but they conflict with other pending 
> series doing clk_hw cleanups:
> 
>      https://patchwork.kernel.org/cover/11224933/
>      https://patchwork.kernel.org/cover/11217881/
> 
> Those cleanups would conflict with most imx8m clk changes, it might make 
> sense to wait for them to enter first and then I'll send a v7 of devfreq 
> with solved conflicts and collected acks.
> 
> Shawn / Stephen: How should we proceed?
> 
>> Regards,
>> Chanwoo Choi
>>
>> On 11/15/19 3:33 AM, Leonard Crestez wrote:
>>> Add driver for dynamic scaling the DDR Controller on imx8m chips. Actual
>>> frequency switching is implemented inside TF-A, this driver wraps the
>>> SMC calls and synchronizes the clk tree.
>>>
>>> The DRAM clocks on imx8m have the following structure (abridged):
>>>
>>>   +----------+       |\            +------+
>>>   | dram_pll |-------|M| dram_core |      |
>>>   +----------+       |U|---------->| D    |
>>>                   /--|X|           |  D   |
>>>     dram_alt_root |  |/            |   R  |
>>>                   |                |    C |
>>>              +---------+           |      |
>>>              |FIX DIV/4|           |      |
>>>              +---------+           |      |
>>>    composite:     |                |      |
>>>   +----------+    |                |      |
>>>   | dram_alt |----/                |      |
>>>   +----------+                     |      |
>>>   | dram_apb |-------------------->|      |
>>>   +----------+                     +------+
>>>
>>> The dram_pll is used for higher rates and dram_alt is used for lower
>>> rates. The dram_alt and dram_apb clocks are "imx composite" and their
>>> parent can also be modified.
>>>
>>> This driver will prepare/enable the new parents ahead of switching (so
>>> that the expected roots are enabled) and afterwards it will call
>>> clk_set_parent to ensure the parents in clock framework are up-to-date.
>>>
>>> The driver relies on dram_pll dram_alt and dram_apb being marked with
>>> CLK_GET_RATE_NOCACHE for rate updates.
>>>
>>> Signed-off-by: Leonard Crestez <[e-mail]>
>>> ---
>>>   drivers/devfreq/Kconfig      |   9 +
>>>   drivers/devfreq/Makefile     |   1 +
>>>   drivers/devfreq/imx8m-ddrc.c | 465 +++++++++++++++++++++++++++++++++++
>>>   3 files changed, 475 insertions(+)
>>>   create mode 100644 drivers/devfreq/imx8m-ddrc.c
>>>
>>> diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
>>> index 066e6c4efaa2..923a6132e741 100644
>>> --- a/drivers/devfreq/Kconfig
>>> +++ b/drivers/devfreq/Kconfig
>>> @@ -89,10 +89,19 @@ config ARM_EXYNOS_BUS_DEVFREQ
>>>   	  Each memory bus group could contain many memoby bus block. It reads
>>>   	  PPMU counters of memory controllers by using DEVFREQ-event device
>>>   	  and adjusts the operating frequencies and voltages with OPP support.
>>>   	  This does not yet operate with optimal voltages.
>>>   
>>> +config ARM_IMX8M_DDRC_DEVFREQ
>>> +	tristate "i.MX8M DDRC DEVFREQ Driver"
>>> +	depends on ARCH_MXC || COMPILE_TEST
>>> +	select DEVFREQ_GOV_SIMPLE_ONDEMAND
>>> +	select DEVFREQ_GOV_USERSPACE
>>> +	help
>>> +	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
>>> +	  adjusting DRAM frequency.
>>> +
>>>   config ARM_TEGRA_DEVFREQ
>>>   	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
>>>   	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
>>>   		ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
>>>   		ARCH_TEGRA_210_SOC || \
>>> diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
>>> index 338ae8440db6..3eb4d5e6635c 100644
>>> --- a/drivers/devfreq/Makefile
>>> +++ b/drivers/devfreq/Makefile
>>> @@ -7,10 +7,11 @@ obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
>>>   obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
>>>   obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
>>>   
>>>   # DEVFREQ Drivers
>>>   obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
>>> +obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
>>>   obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
>>>   obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
>>>   obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
>>>   
>>>   # DEVFREQ Event Drivers
>>> diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-ddrc.c
>>> new file mode 100644
>>> index 000000000000..fea169619c59
>>> --- /dev/null
>>> +++ b/drivers/devfreq/imx8m-ddrc.c
>>> @@ -0,0 +1,465 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Copyright 2019 NXP
>>> + */
>>> +
>>> +#include <linux/module.h>
>>> +#include <linux/device.h>
>>> +#include <linux/of_device.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/devfreq.h>
>>> +#include <linux/pm_opp.h>
>>> +#include <linux/clk.h>
>>> +#include <linux/clk-provider.h>
>>> +#include <linux/arm-smccc.h>
>>> +
>>> +#define IMX_SIP_DDR_DVFS			0xc2000004
>>> +
>>> +/* Values starting from 0 switch to specific frequency */
>>> +#define IMX_SIP_DDR_FREQ_SET_HIGH		0x00
>>> +
>>> +/* Deprecated after moving IRQ handling to ATF */
>>> +#define IMX_SIP_DDR_DVFS_WAIT_CHANGE		0x0F
>>> +
>>> +/* Query available frequencies. */
>>> +#define IMX_SIP_DDR_DVFS_GET_FREQ_COUNT		0x10
>>> +#define IMX_SIP_DDR_DVFS_GET_FREQ_INFO		0x11
>>> +
>>> +/*
>>> + * This should be in a 1:1 mapping with devicetree OPPs but
>>> + * firmware provides additional info.
>>> + */
>>> +struct imx8m_ddrc_freq {
>>> +	unsigned long rate;
>>> +	unsigned long smcarg;
>>> +	int dram_core_parent_index;
>>> +	int dram_alt_parent_index;
>>> +	int dram_apb_parent_index;
>>> +};
>>> +
>>> +/* Hardware limitation */
>>> +#define IMX8M_DDRC_MAX_FREQ_COUNT 4
>>> +
>>> +/*
>>> + * i.MX8M DRAM Controller clocks have the following structure (abridged):
>>> + *
>>> + * +----------+       |\            +------+
>>> + * | dram_pll |-------|M| dram_core |      |
>>> + * +----------+       |U|---------->| D    |
>>> + *                 /--|X|           |  D   |
>>> + *   dram_alt_root |  |/            |   R  |
>>> + *                 |                |    C |
>>> + *            +---------+           |      |
>>> + *            |FIX DIV/4|           |      |
>>> + *            +---------+           |      |
>>> + *  composite:     |                |      |
>>> + * +----------+    |                |      |
>>> + * | dram_alt |----/                |      |
>>> + * +----------+                     |      |
>>> + * | dram_apb |-------------------->|      |
>>> + * +----------+                     +------+
>>> + *
>>> + * The dram_pll is used for higher rates and dram_alt is used for lower rates.
>>> + *
>>> + * Frequency switching is implemented in TF-A (via SMC call) and can change the
>>> + * configuration of the clocks, including mux parents. The dram_alt and
>>> + * dram_apb clocks are "imx composite" and their parent can change too.
>>> + *
>>> + * We need to prepare/enable the new mux parents head of switching and update
>>> + * their information afterwards.
>>> + */
>>> +struct imx8m_ddrc {
>>> +	struct devfreq_dev_profile profile;
>>> +	struct devfreq *devfreq;
>>> +
>>> +	/* For frequency switching: */
>>> +	struct clk *dram_core;
>>> +	struct clk *dram_pll;
>>> +	struct clk *dram_alt;
>>> +	struct clk *dram_apb;
>>> +
>>> +	int freq_count;
>>> +	struct imx8m_ddrc_freq freq_table[IMX8M_DDRC_MAX_FREQ_COUNT];
>>> +};
>>> +
>>> +static struct imx8m_ddrc_freq *imx8m_ddrc_find_freq(struct imx8m_ddrc *priv,
>>> +						    unsigned long rate)
>>> +{
>>> +	struct imx8m_ddrc_freq *freq;
>>> +	int i;
>>> +
>>> +	/*
>>> +	 * Firmware reports values in MT/s, so we round-down from Hz
>>> +	 * Rounding is extra generous to ensure a match.
>>> +	 */
>>> +	rate = DIV_ROUND_CLOSEST(rate, 250000);
>>> +	for (i = 0; i < priv->freq_count; ++i) {
>>> +		freq = &priv->freq_table[i];
>>> +		if (freq->rate == rate ||
>>> +				freq->rate + 1 == rate ||
>>> +				freq->rate - 1 == rate)
>>> +			return freq;
>>> +	}
>>> +
>>> +	return NULL;
>>> +}
>>> +
>>> +static void imx8m_ddrc_smc_set_freq(int target_freq)
>>> +{
>>> +	struct arm_smccc_res res;
>>> +	u32 online_cpus = 0;
>>> +	int cpu;
>>> +
>>> +	local_irq_disable();
>>> +
>>> +	for_each_online_cpu(cpu)
>>> +		online_cpus |= (1 << (cpu * 8));
>>> +
>>> +	/* change the ddr freqency */
>>> +	arm_smccc_smc(IMX_SIP_DDR_DVFS, target_freq, online_cpus,
>>> +			0, 0, 0, 0, 0, &res);
>>> +
>>> +	local_irq_enable();
>>> +}
>>> +
>>> +static struct clk *clk_get_parent_by_index(struct clk *clk, int index)
>>> +{
>>> +	struct clk_hw *hw;
>>> +
>>> +	hw = clk_hw_get_parent_by_index(__clk_get_hw(clk), index);
>>> +
>>> +	return hw ? hw->clk : NULL;
>>> +}
>>> +
>>> +static int imx8m_ddrc_set_freq(struct device *dev, struct imx8m_ddrc_freq *freq)
>>> +{
>>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>>> +	struct clk *new_dram_core_parent;
>>> +	struct clk *new_dram_alt_parent;
>>> +	struct clk *new_dram_apb_parent;
>>> +	int ret;
>>> +
>>> +	/*
>>> +	 * Fetch new parents
>>> +	 *
>>> +	 * new_dram_alt_parent and new_dram_apb_parent are optional but
>>> +	 * new_dram_core_parent is not.
>>> +	 */
>>> +	new_dram_core_parent = clk_get_parent_by_index(
>>> +			priv->dram_core, freq->dram_core_parent_index - 1);
>>> +	if (!new_dram_core_parent) {
>>> +		dev_err(dev, "failed to fetch new dram_core parent\n");
>>> +		return -EINVAL;
>>> +	}
>>> +	if (freq->dram_alt_parent_index) {
>>> +		new_dram_alt_parent = clk_get_parent_by_index(
>>> +				priv->dram_alt,
>>> +				freq->dram_alt_parent_index - 1);
>>> +		if (!new_dram_alt_parent) {
>>> +			dev_err(dev, "failed to fetch new dram_alt parent\n");
>>> +			return -EINVAL;
>>> +		}
>>> +	} else
>>> +		new_dram_alt_parent = NULL;
>>> +
>>> +	if (freq->dram_apb_parent_index) {
>>> +		new_dram_apb_parent = clk_get_parent_by_index(
>>> +				priv->dram_apb,
>>> +				freq->dram_apb_parent_index - 1);
>>> +		if (!new_dram_apb_parent) {
>>> +			dev_err(dev, "failed to fetch new dram_apb parent\n");
>>> +			return -EINVAL;
>>> +		}
>>> +	} else
>>> +		new_dram_apb_parent = NULL;
>>> +
>>> +	/* increase reference counts and ensure clks are ON before switch */
>>> +	ret = clk_prepare_enable(new_dram_core_parent);
>>> +	if (ret) {
>>> +		dev_err(dev, "failed to enable new dram_core parent: %d\n",
>>> +			ret);
>>> +		goto out;
>>> +	}
>>> +	ret = clk_prepare_enable(new_dram_alt_parent);
>>> +	if (ret) {
>>> +		dev_err(dev, "failed to enable new dram_alt parent: %d\n",
>>> +			ret);
>>> +		goto out_disable_core_parent;
>>> +	}
>>> +	ret = clk_prepare_enable(new_dram_apb_parent);
>>> +	if (ret) {
>>> +		dev_err(dev, "failed to enable new dram_apb parent: %d\n",
>>> +			ret);
>>> +		goto out_disable_alt_parent;
>>> +	}
>>> +
>>> +	imx8m_ddrc_smc_set_freq(freq->smcarg);
>>> +
>>> +	/* update parents in clk tree after switch. */
>>> +	ret = clk_set_parent(priv->dram_core, new_dram_core_parent);
>>> +	if (ret)
>>> +		dev_warn(dev, "failed to set dram_core parent: %d\n", ret);
>>> +	if (new_dram_alt_parent) {
>>> +		ret = clk_set_parent(priv->dram_alt, new_dram_alt_parent);
>>> +		if (ret)
>>> +			dev_warn(dev, "failed to set dram_alt parent: %d\n",
>>> +				 ret);
>>> +	}
>>> +	if (new_dram_apb_parent) {
>>> +		ret = clk_set_parent(priv->dram_apb, new_dram_apb_parent);
>>> +		if (ret)
>>> +			dev_warn(dev, "failed to set dram_apb parent: %d\n",
>>> +				 ret);
>>> +	}
>>> +
>>> +	/*
>>> +	 * Explicitly refresh dram PLL rate.
>>> +	 *
>>> +	 * Even if it's marked with CLK_GET_RATE_NOCACHE the rate will not be
>>> +	 * automatically refreshed when clk_get_rate is called on children.
>>> +	 */
>>> +	clk_get_rate(priv->dram_pll);
>>> +
>>> +	/*
>>> +	 * clk_set_parent transfer the reference count from old parent.
>>> +	 * now we drop extra reference counts used during the switch
>>> +	 */
>>> +	clk_disable_unprepare(new_dram_apb_parent);
>>> +out_disable_alt_parent:
>>> +	clk_disable_unprepare(new_dram_alt_parent);
>>> +out_disable_core_parent:
>>> +	clk_disable_unprepare(new_dram_core_parent);
>>> +out:
>>> +	return ret;
>>> +}
>>> +
>>> +static int imx8m_ddrc_target(struct device *dev, unsigned long *freq, u32 flags)
>>> +{
>>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>>> +	struct imx8m_ddrc_freq *freq_info;
>>> +	struct dev_pm_opp *new_opp;
>>> +	unsigned long old_freq, new_freq;
>>> +	int ret;
>>> +
>>> +	new_opp = devfreq_recommended_opp(dev, freq, flags);
>>> +	if (IS_ERR(new_opp)) {
>>> +		ret = PTR_ERR(new_opp);
>>> +		dev_err(dev, "failed to get recommended opp: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +	dev_pm_opp_put(new_opp);
>>> +
>>> +	old_freq = clk_get_rate(priv->dram_core);
>>> +	if (*freq == old_freq)
>>> +		return 0;
>>> +
>>> +	freq_info = imx8m_ddrc_find_freq(priv, *freq);
>>> +	if (!freq_info)
>>> +		return -EINVAL;
>>> +
>>> +	/*
>>> +	 * Read back the clk rate to verify switch was correct and so that
>>> +	 * we can report it on all error paths.
>>> +	 */
>>> +	ret = imx8m_ddrc_set_freq(dev, freq_info);
>>> +
>>> +	new_freq = clk_get_rate(priv->dram_core);
>>> +	if (ret)
>>> +		dev_err(dev, "ddrc failed freq switch to %lu from %lu: error %d. now at %lu\n",
>>> +			old_freq, *freq, ret, new_freq);
>>> +	else if (*freq != new_freq)
>>> +		dev_err(dev, "ddrc failed freq update to %lu from %lu, now at %lu\n",
>>> +			old_freq, *freq, new_freq);
>>> +	else
>>> +		dev_dbg(dev, "ddrc freq set to %lu (was %lu)\n",
>>> +			*freq, old_freq);
>>> +
>>> +	return ret;
>>> +}
>>> +
>>> +static int imx8m_ddrc_get_cur_freq(struct device *dev, unsigned long *freq)
>>> +{
>>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>>> +
>>> +	*freq = clk_get_rate(priv->dram_core);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int imx8m_ddrc_get_dev_status(struct device *dev,
>>> +				     struct devfreq_dev_status *stat)
>>> +{
>>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>>> +
>>> +	stat->busy_time = 0;
>>> +	stat->total_time = 0;
>>> +	stat->current_frequency = clk_get_rate(priv->dram_core);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int imx8m_ddrc_init_freq_info(struct device *dev)
>>> +{
>>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>>> +	struct arm_smccc_res res;
>>> +	int index;
>>> +
>>> +	/* An error here means DDR DVFS API not supported by firmware */
>>> +	arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_COUNT,
>>> +			0, 0, 0, 0, 0, 0, &res);
>>> +	priv->freq_count = res.a0;
>>> +	if (priv->freq_count <= 0 ||
>>> +			priv->freq_count > IMX8M_DDRC_MAX_FREQ_COUNT)
>>> +		return -ENODEV;
>>> +
>>> +	for (index = 0; index < priv->freq_count; ++index) {
>>> +		struct imx8m_ddrc_freq *freq = &priv->freq_table[index];
>>> +
>>> +		arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_INFO,
>>> +			      index, 0, 0, 0, 0, 0, &res);
>>> +		/* Result should be strictly positive */
>>> +		if ((long)res.a0 <= 0)
>>> +			return -ENODEV;
>>> +
>>> +		freq->rate = res.a0;
>>> +		freq->smcarg = index;
>>> +		freq->dram_core_parent_index = res.a1;
>>> +		freq->dram_alt_parent_index = res.a2;
>>> +		freq->dram_apb_parent_index = res.a3;
>>> +
>>> +		/* dram_core has 2 options: dram_pll or dram_alt_root */
>>> +		if (freq->dram_core_parent_index != 1 &&
>>> +				freq->dram_core_parent_index != 2)
>>> +			return -ENODEV;
>>> +		/* dram_apb and dram_alt have exactly 8 possible parents */
>>> +		if (freq->dram_alt_parent_index > 8 ||
>>> +				freq->dram_apb_parent_index > 8)
>>> +			return -ENODEV;
>>> +		/* dram_core from alt requires explicit dram_alt parent */
>>> +		if (freq->dram_core_parent_index == 2 &&
>>> +				freq->dram_alt_parent_index == 0)
>>> +			return -ENODEV;
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int imx8m_ddrc_check_opps(struct device *dev)
>>> +{
>>> +	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
>>> +	struct imx8m_ddrc_freq *freq_info;
>>> +	struct dev_pm_opp *opp;
>>> +	unsigned long freq;
>>> +	int i, opp_count;
>>> +
>>> +	/* Enumerate DT OPPs and disable those not supported by firmware */
>>> +	opp_count = dev_pm_opp_get_opp_count(dev);
>>> +	if (opp_count < 0)
>>> +		return opp_count;
>>> +	for (i = 0, freq = 0; i < opp_count; ++i, ++freq) {
>>> +		opp = dev_pm_opp_find_freq_ceil(dev, &freq);
>>> +		if (IS_ERR(opp)) {
>>> +			dev_err(dev, "Failed enumerating OPPs: %ld\n",
>>> +				PTR_ERR(opp));
>>> +			return PTR_ERR(opp);
>>> +		}
>>> +		dev_pm_opp_put(opp);
>>> +
>>> +		freq_info = imx8m_ddrc_find_freq(priv, freq);
>>> +		if (!freq_info) {
>>> +			dev_info(dev, "Disable unsupported OPP %luHz %luMT/s\n",
>>> +					freq, DIV_ROUND_CLOSEST(freq, 250000));
>>> +			dev_pm_opp_disable(dev, freq);
>>> +		}
>>> +	}
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static void imx8m_ddrc_exit(struct device *dev)
>>> +{
>>> +	dev_pm_opp_of_remove_table(dev);
>>> +}
>>> +
>>> +static int imx8m_ddrc_probe(struct platform_device *pdev)
>>> +{
>>> +	struct device *dev = &pdev->dev;
>>> +	struct imx8m_ddrc *priv;
>>> +	const char *gov = DEVFREQ_GOV_USERSPACE;
>>> +	int ret;
>>> +
>>> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>>> +	if (!priv)
>>> +		return -ENOMEM;
>>> +
>>> +	platform_set_drvdata(pdev, priv);
>>> +
>>> +	ret = imx8m_ddrc_init_freq_info(dev);
>>> +	if (ret) {
>>> +		dev_err(dev, "failed to init firmware freq info: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	priv->dram_core = devm_clk_get(dev, "core");
>>> +	priv->dram_pll = devm_clk_get(dev, "pll");
>>> +	priv->dram_alt = devm_clk_get(dev, "alt");
>>> +	priv->dram_apb = devm_clk_get(dev, "apb");
>>> +	if (IS_ERR(priv->dram_core) ||
>>> +		IS_ERR(priv->dram_pll) ||
>>> +		IS_ERR(priv->dram_alt) ||
>>> +		IS_ERR(priv->dram_apb)) {
>>> +		ret = PTR_ERR(priv->devfreq);
>>> +		dev_err(dev, "failed to fetch clocks: %d\n", ret);
>>> +		return ret;
>>> +	}
>>> +
>>> +	ret = dev_pm_opp_of_add_table(dev);
>>> +	if (ret < 0) {
>>> +		dev_err(dev, "failed to get OPP table\n");
>>> +		return ret;
>>> +	}
>>> +
>>> +	ret = imx8m_ddrc_check_opps(dev);
>>> +	if (ret < 0)
>>> +		goto err;
>>> +
>>> +	priv->profile.polling_ms = 1000;
>>> +	priv->profile.target = imx8m_ddrc_target;
>>> +	priv->profile.get_dev_status = imx8m_ddrc_get_dev_status;
>>> +	priv->profile.exit = imx8m_ddrc_exit;
>>> +	priv->profile.get_cur_freq = imx8m_ddrc_get_cur_freq;
>>> +	priv->profile.initial_freq = clk_get_rate(priv->dram_core);
>>> +
>>> +	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
>>> +						gov, NULL);
>>> +	if (IS_ERR(priv->devfreq)) {
>>> +		ret = PTR_ERR(priv->devfreq);
>>> +		dev_err(dev, "failed to add devfreq device: %d\n", ret);
>>> +		goto err;
>>> +	}
>>> +
>>> +	return 0;
>>> +
>>> +err:
>>> +	dev_pm_opp_of_remove_table(dev);
>>> +	return ret;
>>> +}
>>> +
>>> +static const struct of_device_id imx8m_ddrc_of_match[] = {
>>> +	{ .compatible = "fsl,imx8m-ddrc", },
>>> +	{ /* sentinel */ },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, imx8m_ddrc_of_match);
>>> +
>>> +static struct platform_driver imx8m_ddrc_platdrv = {
>>> +	.probe		= imx8m_ddrc_probe,
>>> +	.driver = {
>>> +		.name	= "imx8m-ddrc-devfreq",
>>> +		.of_match_table = of_match_ptr(imx8m_ddrc_of_match),
>>> +	},
>>> +};
>>> +module_platform_driver(imx8m_ddrc_platdrv);
>>> +
>>> +MODULE_DESCRIPTION("i.MX8M DDR Controller frequency driver");
>>> +MODULE_AUTHOR("Leonard Crestez <[e-mail]>");
>>> +MODULE_LICENSE("GPL v2");
>>>
>>
> 
> 
> 

Applied patch3/patch4 for v5.6-rc1. Thanks.

Patch

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index 066e6c4efaa2..923a6132e741 100644
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -89,10 +89,19 @@  config ARM_EXYNOS_BUS_DEVFREQ
 	  Each memory bus group could contain many memoby bus block. It reads
 	  PPMU counters of memory controllers by using DEVFREQ-event device
 	  and adjusts the operating frequencies and voltages with OPP support.
 	  This does not yet operate with optimal voltages.
 
+config ARM_IMX8M_DDRC_DEVFREQ
+	tristate "i.MX8M DDRC DEVFREQ Driver"
+	depends on ARCH_MXC || COMPILE_TEST
+	select DEVFREQ_GOV_SIMPLE_ONDEMAND
+	select DEVFREQ_GOV_USERSPACE
+	help
+	  This adds the DEVFREQ driver for the i.MX8M DDR Controller. It allows
+	  adjusting DRAM frequency.
+
 config ARM_TEGRA_DEVFREQ
 	tristate "NVIDIA Tegra30/114/124/210 DEVFREQ Driver"
 	depends on ARCH_TEGRA_3x_SOC || ARCH_TEGRA_114_SOC || \
 		ARCH_TEGRA_132_SOC || ARCH_TEGRA_124_SOC || \
 		ARCH_TEGRA_210_SOC || \
diff --git a/drivers/devfreq/Makefile b/drivers/devfreq/Makefile
index 338ae8440db6..3eb4d5e6635c 100644
--- a/drivers/devfreq/Makefile
+++ b/drivers/devfreq/Makefile
@@ -7,10 +7,11 @@  obj-$(CONFIG_DEVFREQ_GOV_POWERSAVE)	+= governor_powersave.o
 obj-$(CONFIG_DEVFREQ_GOV_USERSPACE)	+= governor_userspace.o
 obj-$(CONFIG_DEVFREQ_GOV_PASSIVE)	+= governor_passive.o
 
 # DEVFREQ Drivers
 obj-$(CONFIG_ARM_EXYNOS_BUS_DEVFREQ)	+= exynos-bus.o
+obj-$(CONFIG_ARM_IMX8M_DDRC_DEVFREQ)	+= imx8m-ddrc.o
 obj-$(CONFIG_ARM_RK3399_DMC_DEVFREQ)	+= rk3399_dmc.o
 obj-$(CONFIG_ARM_TEGRA_DEVFREQ)		+= tegra30-devfreq.o
 obj-$(CONFIG_ARM_TEGRA20_DEVFREQ)	+= tegra20-devfreq.o
 
 # DEVFREQ Event Drivers
diff --git a/drivers/devfreq/imx8m-ddrc.c b/drivers/devfreq/imx8m-ddrc.c
new file mode 100644
index 000000000000..fea169619c59
--- /dev/null
+++ b/drivers/devfreq/imx8m-ddrc.c
@@ -0,0 +1,465 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2019 NXP
+ */
+
+#include <linux/module.h>
+#include <linux/device.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/devfreq.h>
+#include <linux/pm_opp.h>
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/arm-smccc.h>
+
+#define IMX_SIP_DDR_DVFS			0xc2000004
+
+/* Values starting from 0 switch to specific frequency */
+#define IMX_SIP_DDR_FREQ_SET_HIGH		0x00
+
+/* Deprecated after moving IRQ handling to ATF */
+#define IMX_SIP_DDR_DVFS_WAIT_CHANGE		0x0F
+
+/* Query available frequencies. */
+#define IMX_SIP_DDR_DVFS_GET_FREQ_COUNT		0x10
+#define IMX_SIP_DDR_DVFS_GET_FREQ_INFO		0x11
+
+/*
+ * This should be in a 1:1 mapping with devicetree OPPs but
+ * firmware provides additional info.
+ */
+struct imx8m_ddrc_freq {
+	unsigned long rate;
+	unsigned long smcarg;
+	int dram_core_parent_index;
+	int dram_alt_parent_index;
+	int dram_apb_parent_index;
+};
+
+/* Hardware limitation */
+#define IMX8M_DDRC_MAX_FREQ_COUNT 4
+
+/*
+ * i.MX8M DRAM Controller clocks have the following structure (abridged):
+ *
+ * +----------+       |\            +------+
+ * | dram_pll |-------|M| dram_core |      |
+ * +----------+       |U|---------->| D    |
+ *                 /--|X|           |  D   |
+ *   dram_alt_root |  |/            |   R  |
+ *                 |                |    C |
+ *            +---------+           |      |
+ *            |FIX DIV/4|           |      |
+ *            +---------+           |      |
+ *  composite:     |                |      |
+ * +----------+    |                |      |
+ * | dram_alt |----/                |      |
+ * +----------+                     |      |
+ * | dram_apb |-------------------->|      |
+ * +----------+                     +------+
+ *
+ * The dram_pll is used for higher rates and dram_alt is used for lower rates.
+ *
+ * Frequency switching is implemented in TF-A (via SMC call) and can change the
+ * configuration of the clocks, including mux parents. The dram_alt and
+ * dram_apb clocks are "imx composite" and their parent can change too.
+ *
+ * We need to prepare/enable the new mux parents head of switching and update
+ * their information afterwards.
+ */
+struct imx8m_ddrc {
+	struct devfreq_dev_profile profile;
+	struct devfreq *devfreq;
+
+	/* For frequency switching: */
+	struct clk *dram_core;
+	struct clk *dram_pll;
+	struct clk *dram_alt;
+	struct clk *dram_apb;
+
+	int freq_count;
+	struct imx8m_ddrc_freq freq_table[IMX8M_DDRC_MAX_FREQ_COUNT];
+};
+
+static struct imx8m_ddrc_freq *imx8m_ddrc_find_freq(struct imx8m_ddrc *priv,
+						    unsigned long rate)
+{
+	struct imx8m_ddrc_freq *freq;
+	int i;
+
+	/*
+	 * Firmware reports values in MT/s, so we round-down from Hz
+	 * Rounding is extra generous to ensure a match.
+	 */
+	rate = DIV_ROUND_CLOSEST(rate, 250000);
+	for (i = 0; i < priv->freq_count; ++i) {
+		freq = &priv->freq_table[i];
+		if (freq->rate == rate ||
+				freq->rate + 1 == rate ||
+				freq->rate - 1 == rate)
+			return freq;
+	}
+
+	return NULL;
+}
+
+static void imx8m_ddrc_smc_set_freq(int target_freq)
+{
+	struct arm_smccc_res res;
+	u32 online_cpus = 0;
+	int cpu;
+
+	local_irq_disable();
+
+	for_each_online_cpu(cpu)
+		online_cpus |= (1 << (cpu * 8));
+
+	/* change the ddr freqency */
+	arm_smccc_smc(IMX_SIP_DDR_DVFS, target_freq, online_cpus,
+			0, 0, 0, 0, 0, &res);
+
+	local_irq_enable();
+}
+
+static struct clk *clk_get_parent_by_index(struct clk *clk, int index)
+{
+	struct clk_hw *hw;
+
+	hw = clk_hw_get_parent_by_index(__clk_get_hw(clk), index);
+
+	return hw ? hw->clk : NULL;
+}
+
+static int imx8m_ddrc_set_freq(struct device *dev, struct imx8m_ddrc_freq *freq)
+{
+	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
+	struct clk *new_dram_core_parent;
+	struct clk *new_dram_alt_parent;
+	struct clk *new_dram_apb_parent;
+	int ret;
+
+	/*
+	 * Fetch new parents
+	 *
+	 * new_dram_alt_parent and new_dram_apb_parent are optional but
+	 * new_dram_core_parent is not.
+	 */
+	new_dram_core_parent = clk_get_parent_by_index(
+			priv->dram_core, freq->dram_core_parent_index - 1);
+	if (!new_dram_core_parent) {
+		dev_err(dev, "failed to fetch new dram_core parent\n");
+		return -EINVAL;
+	}
+	if (freq->dram_alt_parent_index) {
+		new_dram_alt_parent = clk_get_parent_by_index(
+				priv->dram_alt,
+				freq->dram_alt_parent_index - 1);
+		if (!new_dram_alt_parent) {
+			dev_err(dev, "failed to fetch new dram_alt parent\n");
+			return -EINVAL;
+		}
+	} else
+		new_dram_alt_parent = NULL;
+
+	if (freq->dram_apb_parent_index) {
+		new_dram_apb_parent = clk_get_parent_by_index(
+				priv->dram_apb,
+				freq->dram_apb_parent_index - 1);
+		if (!new_dram_apb_parent) {
+			dev_err(dev, "failed to fetch new dram_apb parent\n");
+			return -EINVAL;
+		}
+	} else
+		new_dram_apb_parent = NULL;
+
+	/* increase reference counts and ensure clks are ON before switch */
+	ret = clk_prepare_enable(new_dram_core_parent);
+	if (ret) {
+		dev_err(dev, "failed to enable new dram_core parent: %d\n",
+			ret);
+		goto out;
+	}
+	ret = clk_prepare_enable(new_dram_alt_parent);
+	if (ret) {
+		dev_err(dev, "failed to enable new dram_alt parent: %d\n",
+			ret);
+		goto out_disable_core_parent;
+	}
+	ret = clk_prepare_enable(new_dram_apb_parent);
+	if (ret) {
+		dev_err(dev, "failed to enable new dram_apb parent: %d\n",
+			ret);
+		goto out_disable_alt_parent;
+	}
+
+	imx8m_ddrc_smc_set_freq(freq->smcarg);
+
+	/* update parents in clk tree after switch. */
+	ret = clk_set_parent(priv->dram_core, new_dram_core_parent);
+	if (ret)
+		dev_warn(dev, "failed to set dram_core parent: %d\n", ret);
+	if (new_dram_alt_parent) {
+		ret = clk_set_parent(priv->dram_alt, new_dram_alt_parent);
+		if (ret)
+			dev_warn(dev, "failed to set dram_alt parent: %d\n",
+				 ret);
+	}
+	if (new_dram_apb_parent) {
+		ret = clk_set_parent(priv->dram_apb, new_dram_apb_parent);
+		if (ret)
+			dev_warn(dev, "failed to set dram_apb parent: %d\n",
+				 ret);
+	}
+
+	/*
+	 * Explicitly refresh dram PLL rate.
+	 *
+	 * Even if it's marked with CLK_GET_RATE_NOCACHE the rate will not be
+	 * automatically refreshed when clk_get_rate is called on children.
+	 */
+	clk_get_rate(priv->dram_pll);
+
+	/*
+	 * clk_set_parent transfer the reference count from old parent.
+	 * now we drop extra reference counts used during the switch
+	 */
+	clk_disable_unprepare(new_dram_apb_parent);
+out_disable_alt_parent:
+	clk_disable_unprepare(new_dram_alt_parent);
+out_disable_core_parent:
+	clk_disable_unprepare(new_dram_core_parent);
+out:
+	return ret;
+}
+
+static int imx8m_ddrc_target(struct device *dev, unsigned long *freq, u32 flags)
+{
+	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
+	struct imx8m_ddrc_freq *freq_info;
+	struct dev_pm_opp *new_opp;
+	unsigned long old_freq, new_freq;
+	int ret;
+
+	new_opp = devfreq_recommended_opp(dev, freq, flags);
+	if (IS_ERR(new_opp)) {
+		ret = PTR_ERR(new_opp);
+		dev_err(dev, "failed to get recommended opp: %d\n", ret);
+		return ret;
+	}
+	dev_pm_opp_put(new_opp);
+
+	old_freq = clk_get_rate(priv->dram_core);
+	if (*freq == old_freq)
+		return 0;
+
+	freq_info = imx8m_ddrc_find_freq(priv, *freq);
+	if (!freq_info)
+		return -EINVAL;
+
+	/*
+	 * Read back the clk rate to verify switch was correct and so that
+	 * we can report it on all error paths.
+	 */
+	ret = imx8m_ddrc_set_freq(dev, freq_info);
+
+	new_freq = clk_get_rate(priv->dram_core);
+	if (ret)
+		dev_err(dev, "ddrc failed freq switch to %lu from %lu: error %d. now at %lu\n",
+			old_freq, *freq, ret, new_freq);
+	else if (*freq != new_freq)
+		dev_err(dev, "ddrc failed freq update to %lu from %lu, now at %lu\n",
+			old_freq, *freq, new_freq);
+	else
+		dev_dbg(dev, "ddrc freq set to %lu (was %lu)\n",
+			*freq, old_freq);
+
+	return ret;
+}
+
+static int imx8m_ddrc_get_cur_freq(struct device *dev, unsigned long *freq)
+{
+	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
+
+	*freq = clk_get_rate(priv->dram_core);
+
+	return 0;
+}
+
+static int imx8m_ddrc_get_dev_status(struct device *dev,
+				     struct devfreq_dev_status *stat)
+{
+	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
+
+	stat->busy_time = 0;
+	stat->total_time = 0;
+	stat->current_frequency = clk_get_rate(priv->dram_core);
+
+	return 0;
+}
+
+static int imx8m_ddrc_init_freq_info(struct device *dev)
+{
+	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
+	struct arm_smccc_res res;
+	int index;
+
+	/* An error here means DDR DVFS API not supported by firmware */
+	arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_COUNT,
+			0, 0, 0, 0, 0, 0, &res);
+	priv->freq_count = res.a0;
+	if (priv->freq_count <= 0 ||
+			priv->freq_count > IMX8M_DDRC_MAX_FREQ_COUNT)
+		return -ENODEV;
+
+	for (index = 0; index < priv->freq_count; ++index) {
+		struct imx8m_ddrc_freq *freq = &priv->freq_table[index];
+
+		arm_smccc_smc(IMX_SIP_DDR_DVFS, IMX_SIP_DDR_DVFS_GET_FREQ_INFO,
+			      index, 0, 0, 0, 0, 0, &res);
+		/* Result should be strictly positive */
+		if ((long)res.a0 <= 0)
+			return -ENODEV;
+
+		freq->rate = res.a0;
+		freq->smcarg = index;
+		freq->dram_core_parent_index = res.a1;
+		freq->dram_alt_parent_index = res.a2;
+		freq->dram_apb_parent_index = res.a3;
+
+		/* dram_core has 2 options: dram_pll or dram_alt_root */
+		if (freq->dram_core_parent_index != 1 &&
+				freq->dram_core_parent_index != 2)
+			return -ENODEV;
+		/* dram_apb and dram_alt have exactly 8 possible parents */
+		if (freq->dram_alt_parent_index > 8 ||
+				freq->dram_apb_parent_index > 8)
+			return -ENODEV;
+		/* dram_core from alt requires explicit dram_alt parent */
+		if (freq->dram_core_parent_index == 2 &&
+				freq->dram_alt_parent_index == 0)
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+static int imx8m_ddrc_check_opps(struct device *dev)
+{
+	struct imx8m_ddrc *priv = dev_get_drvdata(dev);
+	struct imx8m_ddrc_freq *freq_info;
+	struct dev_pm_opp *opp;
+	unsigned long freq;
+	int i, opp_count;
+
+	/* Enumerate DT OPPs and disable those not supported by firmware */
+	opp_count = dev_pm_opp_get_opp_count(dev);
+	if (opp_count < 0)
+		return opp_count;
+	for (i = 0, freq = 0; i < opp_count; ++i, ++freq) {
+		opp = dev_pm_opp_find_freq_ceil(dev, &freq);
+		if (IS_ERR(opp)) {
+			dev_err(dev, "Failed enumerating OPPs: %ld\n",
+				PTR_ERR(opp));
+			return PTR_ERR(opp);
+		}
+		dev_pm_opp_put(opp);
+
+		freq_info = imx8m_ddrc_find_freq(priv, freq);
+		if (!freq_info) {
+			dev_info(dev, "Disable unsupported OPP %luHz %luMT/s\n",
+					freq, DIV_ROUND_CLOSEST(freq, 250000));
+			dev_pm_opp_disable(dev, freq);
+		}
+	}
+
+	return 0;
+}
+
+static void imx8m_ddrc_exit(struct device *dev)
+{
+	dev_pm_opp_of_remove_table(dev);
+}
+
+static int imx8m_ddrc_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct imx8m_ddrc *priv;
+	const char *gov = DEVFREQ_GOV_USERSPACE;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	platform_set_drvdata(pdev, priv);
+
+	ret = imx8m_ddrc_init_freq_info(dev);
+	if (ret) {
+		dev_err(dev, "failed to init firmware freq info: %d\n", ret);
+		return ret;
+	}
+
+	priv->dram_core = devm_clk_get(dev, "core");
+	priv->dram_pll = devm_clk_get(dev, "pll");
+	priv->dram_alt = devm_clk_get(dev, "alt");
+	priv->dram_apb = devm_clk_get(dev, "apb");
+	if (IS_ERR(priv->dram_core) ||
+		IS_ERR(priv->dram_pll) ||
+		IS_ERR(priv->dram_alt) ||
+		IS_ERR(priv->dram_apb)) {
+		ret = PTR_ERR(priv->devfreq);
+		dev_err(dev, "failed to fetch clocks: %d\n", ret);
+		return ret;
+	}
+
+	ret = dev_pm_opp_of_add_table(dev);
+	if (ret < 0) {
+		dev_err(dev, "failed to get OPP table\n");
+		return ret;
+	}
+
+	ret = imx8m_ddrc_check_opps(dev);
+	if (ret < 0)
+		goto err;
+
+	priv->profile.polling_ms = 1000;
+	priv->profile.target = imx8m_ddrc_target;
+	priv->profile.get_dev_status = imx8m_ddrc_get_dev_status;
+	priv->profile.exit = imx8m_ddrc_exit;
+	priv->profile.get_cur_freq = imx8m_ddrc_get_cur_freq;
+	priv->profile.initial_freq = clk_get_rate(priv->dram_core);
+
+	priv->devfreq = devm_devfreq_add_device(dev, &priv->profile,
+						gov, NULL);
+	if (IS_ERR(priv->devfreq)) {
+		ret = PTR_ERR(priv->devfreq);
+		dev_err(dev, "failed to add devfreq device: %d\n", ret);
+		goto err;
+	}
+
+	return 0;
+
+err:
+	dev_pm_opp_of_remove_table(dev);
+	return ret;
+}
+
+static const struct of_device_id imx8m_ddrc_of_match[] = {
+	{ .compatible = "fsl,imx8m-ddrc", },
+	{ /* sentinel */ },
+};
+MODULE_DEVICE_TABLE(of, imx8m_ddrc_of_match);
+
+static struct platform_driver imx8m_ddrc_platdrv = {
+	.probe		= imx8m_ddrc_probe,
+	.driver = {
+		.name	= "imx8m-ddrc-devfreq",
+		.of_match_table = of_match_ptr(imx8m_ddrc_of_match),
+	},
+};
+module_platform_driver(imx8m_ddrc_platdrv);
+
+MODULE_DESCRIPTION("i.MX8M DDR Controller frequency driver");
+MODULE_AUTHOR("Leonard Crestez <[e-mail]>");
+MODULE_LICENSE("GPL v2");