diff mbox

cpufreq: brcmstb-cpufreq: CPUfreq driver for older Broadcom STB SoCs

Message ID 20161110235601.71395-1-code@mmayer.net (mailing list archive)
State Superseded, archived
Headers show

Commit Message

Markus Mayer Nov. 10, 2016, 11:56 p.m. UTC
From: Markus Mayer <mmayer@broadcom.com>

This CPUfreq driver provides basic frequency scaling for older Broadcom
STB SoCs that do not use AVS firmware with DVFS support. There is no
support for voltage scaling.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
---

This patch is based on Rafael's "bleeding-edge" branch.

 drivers/cpufreq/Kconfig.arm       |  12 ++
 drivers/cpufreq/Makefile          |   1 +
 drivers/cpufreq/brcmstb-cpufreq.c | 407 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 420 insertions(+)
 create mode 100644 drivers/cpufreq/brcmstb-cpufreq.c

Comments

kernel test robot Nov. 11, 2016, 6:14 a.m. UTC | #1
Hi Markus,

[auto build test ERROR on pm/linux-next]
[also build test ERROR on next-20161110]
[cannot apply to v4.9-rc4]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Markus-Mayer/cpufreq-brcmstb-cpufreq-CPUfreq-driver-for-older-Broadcom-STB-SoCs/20161111-075914
base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
config: arm-allmodconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=arm 

All errors (new ones prefixed by >>):

>> FATAL: drivers/cpufreq/brcmstb-cpufreq: sizeof(struct platform_device_id)=24 is not a modulo of the size of section __mod_platform__<identifier>_device_table=392.
>> Fix definition of struct platform_device_id in mod_devicetable.h

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
Markus Mayer Nov. 11, 2016, 7 p.m. UTC | #2
On 10 November 2016 at 22:14, kbuild test robot <lkp@intel.com> wrote:
> Hi Markus,
>
> [auto build test ERROR on pm/linux-next]
> [also build test ERROR on next-20161110]
> [cannot apply to v4.9-rc4]
> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>
> url:    https://github.com/0day-ci/linux/commits/Markus-Mayer/cpufreq-brcmstb-cpufreq-CPUfreq-driver-for-older-Broadcom-STB-SoCs/20161111-075914
> base:   https://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm.git linux-next
> config: arm-allmodconfig (attached as .config)
> compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
> reproduce:
>         wget https://git.kernel.org/cgit/linux/kernel/git/wfg/lkp-tests.git/plain/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # save the attached .config to linux build tree
>         make.cross ARCH=arm
>
> All errors (new ones prefixed by >>):
>
>>> FATAL: drivers/cpufreq/brcmstb-cpufreq: sizeof(struct platform_device_id)=24 is not a modulo of the size of section __mod_platform__<identifier>_device_table=392.
>>> Fix definition of struct platform_device_id in mod_devicetable.h

This is a strange one. It does apply to Rafael's pm-linux/linux-next
branch when I do it manually. It also builds.

  CHK     include/config/kernel.release
  CHK     include/generated/uapi/linux/version.h
  CHK     include/generated/utsrelease.h
  CHK     include/generated/timeconst.h
  CHK     include/generated/bounds.h
  CHK     include/generated/asm-offsets.h
  CALL    scripts/checksyscalls.sh
  CHK     include/generated/compile.h
  EXPORTS arch/arm/lib/lib-ksyms.o
  LD      arch/arm/lib/built-in.o
  CC      drivers/cpufreq/brcmstb-cpufreq.o
  EXPORTS lib/lib-ksyms.o
  LD      drivers/cpufreq/built-in.o
  LD      lib/built-in.o
  EXPORTS drivers/firmware/efi/libstub/lib-ksyms.o
  LD      drivers/firmware/efi/libstub/built-in.o
  LD      drivers/firmware/efi/built-in.o
  LD      drivers/firmware/built-in.o
  LD      drivers/built-in.o
  LD      vmlinux.o
  MODPOST vmlinux.o
[...]

I used the linux-next branch from here:
https://git.kernel.org/cgit/linux/kernel/git/rafael/linux-pm.git

Regards,
-Markus

> ---
> 0-DAY kernel test infrastructure                Open Source Technology Center
> https://lists.01.org/pipermail/kbuild-all                   Intel Corporation
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Viresh Kumar Nov. 17, 2016, 9:02 a.m. UTC | #3
On 10-11-16, 15:56, Markus Mayer wrote:
> From: Markus Mayer <mmayer@broadcom.com>
> 
> This CPUfreq driver provides basic frequency scaling for older Broadcom
> STB SoCs that do not use AVS firmware with DVFS support. There is no
> support for voltage scaling.
> 
> Signed-off-by: Markus Mayer <mmayer@broadcom.com>
> ---
> 
> This patch is based on Rafael's "bleeding-edge" branch.
> 
>  drivers/cpufreq/Kconfig.arm       |  12 ++
>  drivers/cpufreq/Makefile          |   1 +
>  drivers/cpufreq/brcmstb-cpufreq.c | 407 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 420 insertions(+)
>  create mode 100644 drivers/cpufreq/brcmstb-cpufreq.c
> 
> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
> index 920c469..36422af 100644
> --- a/drivers/cpufreq/Kconfig.arm
> +++ b/drivers/cpufreq/Kconfig.arm
> @@ -33,6 +33,18 @@ config ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
>  
>  	  If in doubt, say N.
>  
> +config ARM_BRCMSTB_CPUFREQ
> +	tristate "Broadcom STB CPUfreq driver"
> +	depends on ARCH_BRCMSTB || COMPILE_TEST
> +	default y
> +	help
> +	  Some Broadcom SoCs offer multiple operating frequencies that CPUfreq
> +	  can take advantage of to improve energy efficiency.
> +
> +	  Say Y, if you have a supported Broadcom SoC. If your Broadcom SoC
> +	  has AVS firmware with support for frequency and voltage scaling,
> +	  say N here and enable ARM_BRCMSTB_AVS_CPUFREQ instead.
> +
>  config ARM_DT_BL_CPUFREQ
>  	tristate "Generic probing via DT for ARM big LITTLE CPUfreq driver"
>  	depends on ARM_BIG_LITTLE_CPUFREQ && OF
> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
> index 1e46c39..23700aa 100644
> --- a/drivers/cpufreq/Makefile
> +++ b/drivers/cpufreq/Makefile
> @@ -52,6 +52,7 @@ obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ)	+= arm_big_little.o
>  obj-$(CONFIG_ARM_DT_BL_CPUFREQ)		+= arm_big_little_dt.o
>  
>  obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ)	+= brcmstb-avs-cpufreq.o
> +obj-$(CONFIG_ARM_BRCMSTB_CPUFREQ)	+= brcmstb-cpufreq.o
>  obj-$(CONFIG_ARCH_DAVINCI)		+= davinci-cpufreq.o
>  obj-$(CONFIG_UX500_SOC_DB8500)		+= dbx500-cpufreq.o
>  obj-$(CONFIG_ARM_EXYNOS5440_CPUFREQ)	+= exynos5440-cpufreq.o
> diff --git a/drivers/cpufreq/brcmstb-cpufreq.c b/drivers/cpufreq/brcmstb-cpufreq.c
> new file mode 100644
> index 0000000..419638a
> --- /dev/null
> +++ b/drivers/cpufreq/brcmstb-cpufreq.c
> @@ -0,0 +1,407 @@
> +/*
> + * CPU frequency scaling for Broadcom set top box SoCs
> + *
> + * Copyright (c) 2016 Broadcom
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License as
> + * published by the Free Software Foundation version 2.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clk-provider.h>
> +#include <linux/cpufreq.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/platform_device.h>
> +
> +#define BRCMSTB_CPUFREQ_PREFIX	"brcmstb"
> +#define BRCMSTB_CPUFREQ_NAME	BRCMSTB_CPUFREQ_PREFIX "-cpufreq"
> +
> +/* We search for these compatible strings. */
> +#define BRCMSTB_DT_CPU_CLK_CTRL	"brcm,brcmstb-cpu-clk-div"
> +#define BRCMSTB_DT_MEMC_DDR	"brcm,brcmstb-memc-ddr"
> +#define BRCM_AVS_CPU_DATA	"brcm,avs-cpu-data-mem"
> +
> +/* We also need a few clocks in device tree. These are node names. */
> +#define BRCMSTB_CLK_MDIV_CH0	"cpu_mdiv_ch0"
> +#define BRCMSTB_CLK_NDIV_INT	"cpu_ndiv_int"
> +#define BRCMSTB_CLK_SW_SCB	"sw_scb"
> +
> +#define BRCMSTB_TBL_SAFE_MODE	BIT(0)
> +#define BRCMSTB_REG_SAFE_MODE	BIT(4)
> +
> +/* This is as low as we'll go in the frequency table. */
> +#define MIN_CPU_FREQ		(100 * 1000)	/* in kHz */
> +
> +struct private_data {
> +	void __iomem *cpu_clk_ctrl_reg;
> +	struct device *dev;
> +};
> +
> +/* Count the active memory controllers in the system. */
> +static int count_memory_controllers(void)
> +{
> +	struct device_node *np = NULL;
> +	int i = 0;
> +
> +	do {
> +		np = of_find_compatible_node(np, NULL, BRCMSTB_DT_MEMC_DDR);
> +		if (of_device_is_available(np))
> +			i++;
> +		of_node_put(np);
> +	} while (np);
> +
> +	return i;
> +}
> +
> +static int get_frequencies(const struct cpufreq_policy *policy,
> +			   unsigned int *vco_freq, unsigned int *cpu_freq,
> +			   unsigned int *scb_freq)
> +{
> +	struct clk *cpu_ndiv_int, *sw_scb;
> +
> +	cpu_ndiv_int = __clk_lookup(BRCMSTB_CLK_NDIV_INT);
> +	if (!cpu_ndiv_int)
> +		return -ENODEV;
> +
> +	sw_scb = __clk_lookup(BRCMSTB_CLK_SW_SCB);
> +	if (!sw_scb)
> +		return -ENODEV;
> +
> +	/* return frequencies in kHz */
> +	*vco_freq = clk_get_rate(cpu_ndiv_int) / 1000;
> +	*cpu_freq = clk_get_rate(policy->clk) / 1000;
> +	*scb_freq = clk_get_rate(sw_scb) / 1000;
> +
> +	return 0;
> +}
> +
> +/*
> + * Safe mode: When set, the CPU's bus unit is being throttled. This is done to
> + * avoid buffer overflows when the CPU-to-bus-clock ratio is low.
> + *
> + * The formula as to what constitutes a low CPU-to-bus-clock ratio takes into
> + * account the number of memory controllers active in the system and the SCB
> + * frequency. More memory controllers means safe mode is required starting at
> + * higher frequencies.
> + *
> + * For 1 memory controller, cpu_freq/scb_freq must be greater than or equal to
> + * 2 to not require safe mode.
> + *
> + * For 2 or 3 memory controllers, cpu_freq/scb_freq must be greater than or
> + * equal 3 to not require safe mode.
> + */
> +
> +static int freq_requires_safe_mode(unsigned int cpu_freq, unsigned int scb_freq,
> +				   int num_memc)
> +{
> +	unsigned int safe_ratio;
> +
> +	switch (num_memc) {
> +	case 1:
> +		safe_ratio = 2;
> +		break;
> +	case 2:
> +	case 3:
> +		safe_ratio = 3;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}
> +
> +	return ((cpu_freq / scb_freq) < safe_ratio);
> +}
> +
> +static struct cpufreq_frequency_table *
> +brcmstb_get_freq_table(const struct cpufreq_policy *policy)
> +{
> +	unsigned int cpu_freq, vco_freq, scb_freq, mdiv, init_mdiv, f;
> +	struct cpufreq_frequency_table *table;
> +	struct private_data *priv;
> +	int num_memc, ret;
> +	unsigned int i = 0;
> +
> +	ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	priv = policy->driver_data;
> +	num_memc = count_memory_controllers();
> +
> +	/* Calculate the initial mdiv value. We'll increment mdiv from here. */
> +	init_mdiv = vco_freq / cpu_freq;
> +
> +	/* Count how many frequencies we'll offer. */
> +	f = cpu_freq;
> +	for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
> +		/* We only want to use "whole" MHz. */
> +		if ((f % 1000) == 0)
> +			i++;
> +	}
> +
> +	table = devm_kzalloc(priv->dev, (i + 1) * sizeof(*table), GFP_KERNEL);
> +	if (!table)
> +		return ERR_PTR(-ENOMEM);
> +
> +	/* Now, fill the table. */
> +	f = cpu_freq;
> +	i = 0;
> +	for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
> +		if ((f % 1000) == 0) {
> +			table[i].frequency = f;
> +			ret = freq_requires_safe_mode(f, scb_freq, num_memc);
> +			if (ret < 0)
> +				return ERR_PTR(ret);
> +			if (ret > 0)
> +				table[i].driver_data |= BRCMSTB_TBL_SAFE_MODE;
> +			i++;
> +		}
> +	}
> +	table[i].frequency = CPUFREQ_TABLE_END;
> +
> +	return table;
> +}
> +
> +static unsigned int brcmstb_cpufreq_get(unsigned int cpu)
> +{
> +	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> +
> +	return clk_get_rate(policy->clk) / 1000;
> +}

Rather use cpufreq_generic_get().

> +
> +static int brcmstb_target_index(struct cpufreq_policy *policy,
> +				unsigned int index)
> +{
> +	struct cpufreq_frequency_table *entry;
> +	struct private_data *priv;
> +	int ret, safe_mode_needed;
> +	u32 reg;
> +
> +	priv = policy->driver_data;
> +	entry = &policy->freq_table[index];
> +	safe_mode_needed = entry->driver_data & BRCMSTB_TBL_SAFE_MODE;
> +
> +	reg = readl(priv->cpu_clk_ctrl_reg);
> +	if (safe_mode_needed && !(reg & BRCMSTB_REG_SAFE_MODE)) {
> +		reg |= BRCMSTB_REG_SAFE_MODE;
> +		writel(reg, priv->cpu_clk_ctrl_reg);
> +	}
> +	ret = clk_set_rate(policy->clk, entry->frequency * 1000);
> +	if (!ret && !safe_mode_needed && (reg & BRCMSTB_REG_SAFE_MODE)) {
> +		reg &= ~BRCMSTB_REG_SAFE_MODE;
> +		writel(reg, priv->cpu_clk_ctrl_reg);
> +	}
> +
> +	return ret;
> +}
> +
> +/*
> + * All initialization code that we only want to execute once goes here. Setup
> + * code that can be re-tried on every core (if it failed before) can go into
> + * brcm_avs_cpufreq_init().
> + */
> +static int brcmstb_prepare_init(struct platform_device *pdev)
> +{
> +	struct private_data *priv;
> +	struct resource *res;
> +	struct device *dev;
> +
> +	/*
> +	 * If the BRCM STB AVS CPUfreq driver is supported, we bail, so that
> +	 * the more modern approach implementing DVFS in firmware can be used.
> +	 */
> +	if (IS_ENABLED(CONFIG_ARM_BRCM_AVS_CPUFREQ)) {
> +		struct device_node *np;
> +
> +		np = of_find_compatible_node(NULL, NULL, BRCM_AVS_CPU_DATA);
> +		if (np) {
> +			of_node_put(np);
> +			return -ENXIO;
> +		}
> +	}
> +
> +	dev = &pdev->dev;
> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	priv->cpu_clk_ctrl_reg = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(priv->cpu_clk_ctrl_reg)) {
> +		dev_err(dev, "couldn't map DT entry %s\n",
> +			BRCMSTB_DT_CPU_CLK_CTRL);
> +		return -ENODEV;
> +	}
> +
> +	priv->dev = dev;
> +	platform_set_drvdata(pdev, priv);
> +
> +	return 0;
> +}
> +
> +static int brcmstb_cpu_init(struct cpufreq_policy *policy)
> +{
> +	struct cpufreq_frequency_table *freq_table;
> +	struct platform_device *pdev;
> +	struct private_data *priv;
> +	struct clk *cpu_mdiv_ch0;
> +	struct device *dev;
> +	int ret;
> +
> +	cpu_mdiv_ch0 = __clk_lookup(BRCMSTB_CLK_MDIV_CH0);
> +	if (!cpu_mdiv_ch0)
> +		return -ENODEV;
> +
> +	pdev = cpufreq_get_driver_data();
> +	priv = platform_get_drvdata(pdev);
> +	dev = &pdev->dev;
> +
> +	policy->clk = cpu_mdiv_ch0;
> +	policy->driver_data = priv;
> +
> +	freq_table = brcmstb_get_freq_table(policy);
> +	if (IS_ERR(freq_table)) {
> +		ret = PTR_ERR(freq_table);
> +		dev_err(dev, "Couldn't determine frequency table (%d).\n", ret);
> +		if (ret == -EINVAL)
> +			dev_emerg(dev,
> +				"Invalid number of memory controllers -- %d!\n",
> +				count_memory_controllers());
> +		return ret;
> +	}
> +
> +	ret = cpufreq_table_validate_and_show(policy, freq_table);
> +	if (ret) {
> +		dev_err(dev, "invalid frequency table: %d\n", ret);
> +		return ret;
> +	}
> +
> +	dev_info(dev, "registered\n");
> +
> +	/* All cores share the same clock and thus the same policy. */
> +	cpumask_setall(policy->cpus);

You can use cpufreq_generic_init() instead of above two calls.

> +
> +	/* We start at the first entry in the frequency table. */
> +	policy->cur = freq_table[0].frequency;

No, you can't update policy->cur by yourself. Its for the core to
handle it. Though check if you want to use
CPUFREQ_NEED_INITIAL_FREQ_CHECK.

> +
> +	return 0;
> +}
> +
> +/* Shows the number of memory controllers. */
> +static ssize_t show_brcmstb_num_memc(struct cpufreq_policy *policy, char *buf)
> +{
> +	return sprintf(buf, "%u\n", count_memory_controllers());
> +}
> +
> +/* Shows vco_freq, cpu_freq, and scb_freq in kHz. */
> +static ssize_t show_brcmstb_freqs(struct cpufreq_policy *policy, char *buf)
> +{
> +	unsigned int vco_freq, cpu_freq, scb_freq;
> +	int ret;
> +
> +	ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
> +	if (ret)
> +		return sprintf(buf, "<unknown>\n");
> +
> +	return sprintf(buf, "%u %u %u\n", vco_freq, cpu_freq, scb_freq);
> +}
> +
> +/* Shows the lowest frequency (in kHz) that can be used without "safe mode". */
> +static ssize_t show_brcmstb_safe_freq(struct cpufreq_policy *policy, char *buf)
> +{
> +	unsigned int vco_freq, cpu_freq, scb_freq;
> +	unsigned int safe_freq = 0;
> +	int i, num_memc, ret;
> +
> +	ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
> +	if (ret)
> +		return sprintf(buf, "<unknown>\n");
> +
> +	num_memc = count_memory_controllers();
> +
> +	for (i = 0; policy->freq_table[i].frequency != CPUFREQ_TABLE_END; i++) {

You can use cpufreq_for_each_valid_entry() here.

> +		ret = freq_requires_safe_mode(policy->freq_table[i].frequency,
> +					      scb_freq, num_memc);
> +		if (ret < 0)
> +			return sprintf(buf, "<error> (%d)\n", ret);
> +		if (ret == 0)
> +			safe_freq = policy->freq_table[i].frequency;

You don't want to break from the loop here ?

> +	}
> +
> +	return sprintf(buf, "%u\n", safe_freq);
> +}
> +
> +cpufreq_freq_attr_ro(brcmstb_num_memc);
> +cpufreq_freq_attr_ro(brcmstb_freqs);
> +cpufreq_freq_attr_ro(brcmstb_safe_freq);
> +
> +static struct freq_attr *brcmstb_cpufreq_attr[] = {
> +	&cpufreq_freq_attr_scaling_available_freqs,
> +	&brcmstb_num_memc,
> +	&brcmstb_freqs,
> +	&brcmstb_safe_freq,
> +	NULL
> +};
> +
> +static struct cpufreq_driver brcmstb_driver = {
> +	.flags		= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
> +	.verify		= cpufreq_generic_frequency_table_verify,
> +	.target_index	= brcmstb_target_index,
> +	.get		= brcmstb_cpufreq_get,
> +	.init		= brcmstb_cpu_init,

What about .exit ?

> +	.attr		= brcmstb_cpufreq_attr,
> +	.name		= BRCMSTB_CPUFREQ_PREFIX,
> +};
> +
> +static int brcmstb_cpufreq_probe(struct platform_device *pdev)
> +{
> +	int ret;
> +
> +	ret = brcmstb_prepare_init(pdev);
> +	if (ret)
> +		return ret;
> +
> +	brcmstb_driver.driver_data = pdev;
> +
> +	return cpufreq_register_driver(&brcmstb_driver);
> +}
> +
> +static int brcmstb_cpufreq_remove(struct platform_device *pdev)
> +{
> +	int ret;
> +
> +	ret = cpufreq_unregister_driver(&brcmstb_driver);
> +	if (ret)
> +		return ret;
> +
> +	platform_set_drvdata(pdev, NULL);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id brcmstb_cpufreq_match[] = {
> +	{ .compatible = BRCMSTB_DT_CPU_CLK_CTRL },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(platform, brcmstb_cpufreq_match);
> +
> +static struct platform_driver brcmstb_cpufreq_platdrv = {

How is the device getting created for this? Be aware the DT can't have
a separate node for cpufreq-device ..

> +	.driver = {
> +		.name	= BRCMSTB_CPUFREQ_NAME,
> +		.of_match_table = brcmstb_cpufreq_match,
> +	},
> +	.probe		= brcmstb_cpufreq_probe,
> +	.remove		= brcmstb_cpufreq_remove,
> +};
> +module_platform_driver(brcmstb_cpufreq_platdrv);
> +
> +MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
> +MODULE_DESCRIPTION("CPUfreq driver for Broadcom STB SoCs");
> +MODULE_LICENSE("GPL");
Markus Mayer Nov. 17, 2016, 6:38 p.m. UTC | #4
On 17 November 2016 at 01:02, Viresh Kumar <viresh.kumar@linaro.org> wrote:
> On 10-11-16, 15:56, Markus Mayer wrote:
>> From: Markus Mayer <mmayer@broadcom.com>
>>
>> This CPUfreq driver provides basic frequency scaling for older Broadcom
>> STB SoCs that do not use AVS firmware with DVFS support. There is no
>> support for voltage scaling.
>>
>> Signed-off-by: Markus Mayer <mmayer@broadcom.com>
>> ---
>>
>> This patch is based on Rafael's "bleeding-edge" branch.
>>
>>  drivers/cpufreq/Kconfig.arm       |  12 ++
>>  drivers/cpufreq/Makefile          |   1 +
>>  drivers/cpufreq/brcmstb-cpufreq.c | 407 ++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 420 insertions(+)
>>  create mode 100644 drivers/cpufreq/brcmstb-cpufreq.c
>>
>> diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
>> index 920c469..36422af 100644
>> --- a/drivers/cpufreq/Kconfig.arm
>> +++ b/drivers/cpufreq/Kconfig.arm
>> @@ -33,6 +33,18 @@ config ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
>>
>>         If in doubt, say N.
>>
>> +config ARM_BRCMSTB_CPUFREQ
>> +     tristate "Broadcom STB CPUfreq driver"
>> +     depends on ARCH_BRCMSTB || COMPILE_TEST
>> +     default y
>> +     help
>> +       Some Broadcom SoCs offer multiple operating frequencies that CPUfreq
>> +       can take advantage of to improve energy efficiency.
>> +
>> +       Say Y, if you have a supported Broadcom SoC. If your Broadcom SoC
>> +       has AVS firmware with support for frequency and voltage scaling,
>> +       say N here and enable ARM_BRCMSTB_AVS_CPUFREQ instead.
>> +
>>  config ARM_DT_BL_CPUFREQ
>>       tristate "Generic probing via DT for ARM big LITTLE CPUfreq driver"
>>       depends on ARM_BIG_LITTLE_CPUFREQ && OF
>> diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
>> index 1e46c39..23700aa 100644
>> --- a/drivers/cpufreq/Makefile
>> +++ b/drivers/cpufreq/Makefile
>> @@ -52,6 +52,7 @@ obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ)        += arm_big_little.o
>>  obj-$(CONFIG_ARM_DT_BL_CPUFREQ)              += arm_big_little_dt.o
>>
>>  obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ)        += brcmstb-avs-cpufreq.o
>> +obj-$(CONFIG_ARM_BRCMSTB_CPUFREQ)    += brcmstb-cpufreq.o
>>  obj-$(CONFIG_ARCH_DAVINCI)           += davinci-cpufreq.o
>>  obj-$(CONFIG_UX500_SOC_DB8500)               += dbx500-cpufreq.o
>>  obj-$(CONFIG_ARM_EXYNOS5440_CPUFREQ) += exynos5440-cpufreq.o
>> diff --git a/drivers/cpufreq/brcmstb-cpufreq.c b/drivers/cpufreq/brcmstb-cpufreq.c
>> new file mode 100644
>> index 0000000..419638a
>> --- /dev/null
>> +++ b/drivers/cpufreq/brcmstb-cpufreq.c
>> @@ -0,0 +1,407 @@
>> +/*
>> + * CPU frequency scaling for Broadcom set top box SoCs
>> + *
>> + * Copyright (c) 2016 Broadcom
>> + *
>> + * This program is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU General Public License as
>> + * published by the Free Software Foundation version 2.
>> + *
>> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
>> + * kind, whether express or implied; without even the implied warranty
>> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
>> + * GNU General Public License for more details.
>> + */
>> +
>> +#include <linux/clk.h>
>> +#include <linux/clk-provider.h>
>> +#include <linux/cpufreq.h>
>> +#include <linux/module.h>
>> +#include <linux/of_address.h>
>> +#include <linux/platform_device.h>
>> +
>> +#define BRCMSTB_CPUFREQ_PREFIX       "brcmstb"
>> +#define BRCMSTB_CPUFREQ_NAME BRCMSTB_CPUFREQ_PREFIX "-cpufreq"
>> +
>> +/* We search for these compatible strings. */
>> +#define BRCMSTB_DT_CPU_CLK_CTRL      "brcm,brcmstb-cpu-clk-div"
>> +#define BRCMSTB_DT_MEMC_DDR  "brcm,brcmstb-memc-ddr"
>> +#define BRCM_AVS_CPU_DATA    "brcm,avs-cpu-data-mem"
>> +
>> +/* We also need a few clocks in device tree. These are node names. */
>> +#define BRCMSTB_CLK_MDIV_CH0 "cpu_mdiv_ch0"
>> +#define BRCMSTB_CLK_NDIV_INT "cpu_ndiv_int"
>> +#define BRCMSTB_CLK_SW_SCB   "sw_scb"
>> +
>> +#define BRCMSTB_TBL_SAFE_MODE        BIT(0)
>> +#define BRCMSTB_REG_SAFE_MODE        BIT(4)
>> +
>> +/* This is as low as we'll go in the frequency table. */
>> +#define MIN_CPU_FREQ         (100 * 1000)    /* in kHz */
>> +
>> +struct private_data {
>> +     void __iomem *cpu_clk_ctrl_reg;
>> +     struct device *dev;
>> +};
>> +
>> +/* Count the active memory controllers in the system. */
>> +static int count_memory_controllers(void)
>> +{
>> +     struct device_node *np = NULL;
>> +     int i = 0;
>> +
>> +     do {
>> +             np = of_find_compatible_node(np, NULL, BRCMSTB_DT_MEMC_DDR);
>> +             if (of_device_is_available(np))
>> +                     i++;
>> +             of_node_put(np);
>> +     } while (np);
>> +
>> +     return i;
>> +}
>> +
>> +static int get_frequencies(const struct cpufreq_policy *policy,
>> +                        unsigned int *vco_freq, unsigned int *cpu_freq,
>> +                        unsigned int *scb_freq)
>> +{
>> +     struct clk *cpu_ndiv_int, *sw_scb;
>> +
>> +     cpu_ndiv_int = __clk_lookup(BRCMSTB_CLK_NDIV_INT);
>> +     if (!cpu_ndiv_int)
>> +             return -ENODEV;
>> +
>> +     sw_scb = __clk_lookup(BRCMSTB_CLK_SW_SCB);
>> +     if (!sw_scb)
>> +             return -ENODEV;
>> +
>> +     /* return frequencies in kHz */
>> +     *vco_freq = clk_get_rate(cpu_ndiv_int) / 1000;
>> +     *cpu_freq = clk_get_rate(policy->clk) / 1000;
>> +     *scb_freq = clk_get_rate(sw_scb) / 1000;
>> +
>> +     return 0;
>> +}
>> +
>> +/*
>> + * Safe mode: When set, the CPU's bus unit is being throttled. This is done to
>> + * avoid buffer overflows when the CPU-to-bus-clock ratio is low.
>> + *
>> + * The formula as to what constitutes a low CPU-to-bus-clock ratio takes into
>> + * account the number of memory controllers active in the system and the SCB
>> + * frequency. More memory controllers means safe mode is required starting at
>> + * higher frequencies.
>> + *
>> + * For 1 memory controller, cpu_freq/scb_freq must be greater than or equal to
>> + * 2 to not require safe mode.
>> + *
>> + * For 2 or 3 memory controllers, cpu_freq/scb_freq must be greater than or
>> + * equal 3 to not require safe mode.
>> + */
>> +
>> +static int freq_requires_safe_mode(unsigned int cpu_freq, unsigned int scb_freq,
>> +                                int num_memc)
>> +{
>> +     unsigned int safe_ratio;
>> +
>> +     switch (num_memc) {
>> +     case 1:
>> +             safe_ratio = 2;
>> +             break;
>> +     case 2:
>> +     case 3:
>> +             safe_ratio = 3;
>> +             break;
>> +     default:
>> +             return -EINVAL;
>> +     }
>> +
>> +     return ((cpu_freq / scb_freq) < safe_ratio);
>> +}
>> +
>> +static struct cpufreq_frequency_table *
>> +brcmstb_get_freq_table(const struct cpufreq_policy *policy)
>> +{
>> +     unsigned int cpu_freq, vco_freq, scb_freq, mdiv, init_mdiv, f;
>> +     struct cpufreq_frequency_table *table;
>> +     struct private_data *priv;
>> +     int num_memc, ret;
>> +     unsigned int i = 0;
>> +
>> +     ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
>> +     if (ret)
>> +             return ERR_PTR(ret);
>> +
>> +     priv = policy->driver_data;
>> +     num_memc = count_memory_controllers();
>> +
>> +     /* Calculate the initial mdiv value. We'll increment mdiv from here. */
>> +     init_mdiv = vco_freq / cpu_freq;
>> +
>> +     /* Count how many frequencies we'll offer. */
>> +     f = cpu_freq;
>> +     for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
>> +             /* We only want to use "whole" MHz. */
>> +             if ((f % 1000) == 0)
>> +                     i++;
>> +     }
>> +
>> +     table = devm_kzalloc(priv->dev, (i + 1) * sizeof(*table), GFP_KERNEL);
>> +     if (!table)
>> +             return ERR_PTR(-ENOMEM);
>> +
>> +     /* Now, fill the table. */
>> +     f = cpu_freq;
>> +     i = 0;
>> +     for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
>> +             if ((f % 1000) == 0) {
>> +                     table[i].frequency = f;
>> +                     ret = freq_requires_safe_mode(f, scb_freq, num_memc);
>> +                     if (ret < 0)
>> +                             return ERR_PTR(ret);
>> +                     if (ret > 0)
>> +                             table[i].driver_data |= BRCMSTB_TBL_SAFE_MODE;
>> +                     i++;
>> +             }
>> +     }
>> +     table[i].frequency = CPUFREQ_TABLE_END;
>> +
>> +     return table;
>> +}
>> +
>> +static unsigned int brcmstb_cpufreq_get(unsigned int cpu)
>> +{
>> +     struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
>> +
>> +     return clk_get_rate(policy->clk) / 1000;
>> +}
>
> Rather use cpufreq_generic_get().

Done.

>> +
>> +static int brcmstb_target_index(struct cpufreq_policy *policy,
>> +                             unsigned int index)
>> +{
>> +     struct cpufreq_frequency_table *entry;
>> +     struct private_data *priv;
>> +     int ret, safe_mode_needed;
>> +     u32 reg;
>> +
>> +     priv = policy->driver_data;
>> +     entry = &policy->freq_table[index];
>> +     safe_mode_needed = entry->driver_data & BRCMSTB_TBL_SAFE_MODE;
>> +
>> +     reg = readl(priv->cpu_clk_ctrl_reg);
>> +     if (safe_mode_needed && !(reg & BRCMSTB_REG_SAFE_MODE)) {
>> +             reg |= BRCMSTB_REG_SAFE_MODE;
>> +             writel(reg, priv->cpu_clk_ctrl_reg);
>> +     }
>> +     ret = clk_set_rate(policy->clk, entry->frequency * 1000);
>> +     if (!ret && !safe_mode_needed && (reg & BRCMSTB_REG_SAFE_MODE)) {
>> +             reg &= ~BRCMSTB_REG_SAFE_MODE;
>> +             writel(reg, priv->cpu_clk_ctrl_reg);
>> +     }
>> +
>> +     return ret;
>> +}
>> +
>> +/*
>> + * All initialization code that we only want to execute once goes here. Setup
>> + * code that can be re-tried on every core (if it failed before) can go into
>> + * brcm_avs_cpufreq_init().
>> + */
>> +static int brcmstb_prepare_init(struct platform_device *pdev)
>> +{
>> +     struct private_data *priv;
>> +     struct resource *res;
>> +     struct device *dev;
>> +
>> +     /*
>> +      * If the BRCM STB AVS CPUfreq driver is supported, we bail, so that
>> +      * the more modern approach implementing DVFS in firmware can be used.
>> +      */
>> +     if (IS_ENABLED(CONFIG_ARM_BRCM_AVS_CPUFREQ)) {
>> +             struct device_node *np;
>> +
>> +             np = of_find_compatible_node(NULL, NULL, BRCM_AVS_CPU_DATA);
>> +             if (np) {
>> +                     of_node_put(np);
>> +                     return -ENXIO;
>> +             }
>> +     }
>> +
>> +     dev = &pdev->dev;
>> +
>> +     priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>> +     if (!priv)
>> +             return -ENOMEM;
>> +
>> +     res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>> +     priv->cpu_clk_ctrl_reg = devm_ioremap_resource(dev, res);
>> +     if (IS_ERR(priv->cpu_clk_ctrl_reg)) {
>> +             dev_err(dev, "couldn't map DT entry %s\n",
>> +                     BRCMSTB_DT_CPU_CLK_CTRL);
>> +             return -ENODEV;
>> +     }
>> +
>> +     priv->dev = dev;
>> +     platform_set_drvdata(pdev, priv);
>> +
>> +     return 0;
>> +}
>> +
>> +static int brcmstb_cpu_init(struct cpufreq_policy *policy)
>> +{
>> +     struct cpufreq_frequency_table *freq_table;
>> +     struct platform_device *pdev;
>> +     struct private_data *priv;
>> +     struct clk *cpu_mdiv_ch0;
>> +     struct device *dev;
>> +     int ret;
>> +
>> +     cpu_mdiv_ch0 = __clk_lookup(BRCMSTB_CLK_MDIV_CH0);
>> +     if (!cpu_mdiv_ch0)
>> +             return -ENODEV;
>> +
>> +     pdev = cpufreq_get_driver_data();
>> +     priv = platform_get_drvdata(pdev);
>> +     dev = &pdev->dev;
>> +
>> +     policy->clk = cpu_mdiv_ch0;
>> +     policy->driver_data = priv;
>> +
>> +     freq_table = brcmstb_get_freq_table(policy);
>> +     if (IS_ERR(freq_table)) {
>> +             ret = PTR_ERR(freq_table);
>> +             dev_err(dev, "Couldn't determine frequency table (%d).\n", ret);
>> +             if (ret == -EINVAL)
>> +                     dev_emerg(dev,
>> +                             "Invalid number of memory controllers -- %d!\n",
>> +                             count_memory_controllers());
>> +             return ret;
>> +     }
>> +
>> +     ret = cpufreq_table_validate_and_show(policy, freq_table);
>> +     if (ret) {
>> +             dev_err(dev, "invalid frequency table: %d\n", ret);
>> +             return ret;
>> +     }
>> +
>> +     dev_info(dev, "registered\n");
>> +
>> +     /* All cores share the same clock and thus the same policy. */
>> +     cpumask_setall(policy->cpus);
>
> You can use cpufreq_generic_init() instead of above two calls.

Done.

>> +
>> +     /* We start at the first entry in the frequency table. */
>> +     policy->cur = freq_table[0].frequency;
>
> No, you can't update policy->cur by yourself. Its for the core to
> handle it. Though check if you want to use
> CPUFREQ_NEED_INITIAL_FREQ_CHECK.

Yes, that works.

>> +
>> +     return 0;
>> +}
>> +
>> +/* Shows the number of memory controllers. */
>> +static ssize_t show_brcmstb_num_memc(struct cpufreq_policy *policy, char *buf)
>> +{
>> +     return sprintf(buf, "%u\n", count_memory_controllers());
>> +}
>> +
>> +/* Shows vco_freq, cpu_freq, and scb_freq in kHz. */
>> +static ssize_t show_brcmstb_freqs(struct cpufreq_policy *policy, char *buf)
>> +{
>> +     unsigned int vco_freq, cpu_freq, scb_freq;
>> +     int ret;
>> +
>> +     ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
>> +     if (ret)
>> +             return sprintf(buf, "<unknown>\n");
>> +
>> +     return sprintf(buf, "%u %u %u\n", vco_freq, cpu_freq, scb_freq);
>> +}
>> +
>> +/* Shows the lowest frequency (in kHz) that can be used without "safe mode". */
>> +static ssize_t show_brcmstb_safe_freq(struct cpufreq_policy *policy, char *buf)
>> +{
>> +     unsigned int vco_freq, cpu_freq, scb_freq;
>> +     unsigned int safe_freq = 0;
>> +     int i, num_memc, ret;
>> +
>> +     ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
>> +     if (ret)
>> +             return sprintf(buf, "<unknown>\n");
>> +
>> +     num_memc = count_memory_controllers();
>> +
>> +     for (i = 0; policy->freq_table[i].frequency != CPUFREQ_TABLE_END; i++) {
>
> You can use cpufreq_for_each_valid_entry() here.
>
>> +             ret = freq_requires_safe_mode(policy->freq_table[i].frequency,
>> +                                           scb_freq, num_memc);
>> +             if (ret < 0)
>> +                     return sprintf(buf, "<error> (%d)\n", ret);
>> +             if (ret == 0)
>> +                     safe_freq = policy->freq_table[i].frequency;
>
> You don't want to break from the loop here ?

No, because I am trying to find the lowest frequency that doesn't
require safe mode and it's looping through the table from highest to
lowest. So there could still be a lower frequency after the current
one that doesn't require safe mode.

What I can do, however, is something like this:

static ssize_t show_brcmstb_safe_freq(struct cpufreq_policy *policy, char *buf)
{
    struct cpufreq_frequency_table *entry;
    unsigned int safe_freq = 0;

    cpufreq_for_each_valid_entry(entry, policy->freq_table) {
        if (!(entry->driver_data & BRCMSTB_TBL_SAFE_MODE))
            safe_freq = entry->frequency;
   }

    return sprintf(buf, "%u\n", safe_freq);
}

This is using the existing data from the frequency table rather than
re-generating it on the fly by calling freq_requires_safe_mode().

>> +     }
>> +
>> +     return sprintf(buf, "%u\n", safe_freq);
>> +}
>> +
>> +cpufreq_freq_attr_ro(brcmstb_num_memc);
>> +cpufreq_freq_attr_ro(brcmstb_freqs);
>> +cpufreq_freq_attr_ro(brcmstb_safe_freq);
>> +
>> +static struct freq_attr *brcmstb_cpufreq_attr[] = {
>> +     &cpufreq_freq_attr_scaling_available_freqs,
>> +     &brcmstb_num_memc,
>> +     &brcmstb_freqs,
>> +     &brcmstb_safe_freq,
>> +     NULL
>> +};
>> +
>> +static struct cpufreq_driver brcmstb_driver = {
>> +     .flags          = CPUFREQ_NEED_INITIAL_FREQ_CHECK,
>> +     .verify         = cpufreq_generic_frequency_table_verify,
>> +     .target_index   = brcmstb_target_index,
>> +     .get            = brcmstb_cpufreq_get,
>> +     .init           = brcmstb_cpu_init,
>
> What about .exit ?

All my allocations are managed (i.e. using devm* functions), so
cleanup should be automatic. Do I still need one?

>> +     .attr           = brcmstb_cpufreq_attr,
>> +     .name           = BRCMSTB_CPUFREQ_PREFIX,
>> +};
>> +
>> +static int brcmstb_cpufreq_probe(struct platform_device *pdev)
>> +{
>> +     int ret;
>> +
>> +     ret = brcmstb_prepare_init(pdev);
>> +     if (ret)
>> +             return ret;
>> +
>> +     brcmstb_driver.driver_data = pdev;
>> +
>> +     return cpufreq_register_driver(&brcmstb_driver);
>> +}
>> +
>> +static int brcmstb_cpufreq_remove(struct platform_device *pdev)
>> +{
>> +     int ret;
>> +
>> +     ret = cpufreq_unregister_driver(&brcmstb_driver);
>> +     if (ret)
>> +             return ret;
>> +
>> +     platform_set_drvdata(pdev, NULL);
>> +
>> +     return 0;
>> +}
>> +
>> +static const struct of_device_id brcmstb_cpufreq_match[] = {
>> +     { .compatible = BRCMSTB_DT_CPU_CLK_CTRL },
>> +     { }
>> +};
>> +MODULE_DEVICE_TABLE(platform, brcmstb_cpufreq_match);
>> +
>> +static struct platform_driver brcmstb_cpufreq_platdrv = {
>
> How is the device getting created for this? Be aware the DT can't have
> a separate node for cpufreq-device ..

It's using for a clock node (brcm,brcmstb-cpu-clk-div) which exists
independently of this driver.

>> +     .driver = {
>> +             .name   = BRCMSTB_CPUFREQ_NAME,
>> +             .of_match_table = brcmstb_cpufreq_match,
>> +     },
>> +     .probe          = brcmstb_cpufreq_probe,
>> +     .remove         = brcmstb_cpufreq_remove,
>> +};
>> +module_platform_driver(brcmstb_cpufreq_platdrv);
>> +
>> +MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
>> +MODULE_DESCRIPTION("CPUfreq driver for Broadcom STB SoCs");
>> +MODULE_LICENSE("GPL");

Thanks,
-Markus

> --
> viresh
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Viresh Kumar Nov. 18, 2016, 3:09 a.m. UTC | #5
On 17-11-16, 10:38, Markus Mayer wrote:
> No, because I am trying to find the lowest frequency that doesn't
> require safe mode and it's looping through the table from highest to
> lowest. So there could still be a lower frequency after the current
> one that doesn't require safe mode.
> 
> What I can do, however, is something like this:
> 
> static ssize_t show_brcmstb_safe_freq(struct cpufreq_policy *policy, char *buf)
> {
>     struct cpufreq_frequency_table *entry;
>     unsigned int safe_freq = 0;
> 
>     cpufreq_for_each_valid_entry(entry, policy->freq_table) {
>         if (!(entry->driver_data & BRCMSTB_TBL_SAFE_MODE))
>             safe_freq = entry->frequency;
>    }
> 
>     return sprintf(buf, "%u\n", safe_freq);
> }
> 
> This is using the existing data from the frequency table rather than
> re-generating it on the fly by calling freq_requires_safe_mode().


> All my allocations are managed (i.e. using devm* functions), so
> cleanup should be automatic. Do I still need one?


> It's using for a clock node (brcm,brcmstb-cpu-clk-div) which exists
> independently of this driver.

All these seem fine to me.
diff mbox

Patch

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 920c469..36422af 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -33,6 +33,18 @@  config ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
 
 	  If in doubt, say N.
 
+config ARM_BRCMSTB_CPUFREQ
+	tristate "Broadcom STB CPUfreq driver"
+	depends on ARCH_BRCMSTB || COMPILE_TEST
+	default y
+	help
+	  Some Broadcom SoCs offer multiple operating frequencies that CPUfreq
+	  can take advantage of to improve energy efficiency.
+
+	  Say Y, if you have a supported Broadcom SoC. If your Broadcom SoC
+	  has AVS firmware with support for frequency and voltage scaling,
+	  say N here and enable ARM_BRCMSTB_AVS_CPUFREQ instead.
+
 config ARM_DT_BL_CPUFREQ
 	tristate "Generic probing via DT for ARM big LITTLE CPUfreq driver"
 	depends on ARM_BIG_LITTLE_CPUFREQ && OF
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 1e46c39..23700aa 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -52,6 +52,7 @@  obj-$(CONFIG_ARM_BIG_LITTLE_CPUFREQ)	+= arm_big_little.o
 obj-$(CONFIG_ARM_DT_BL_CPUFREQ)		+= arm_big_little_dt.o
 
 obj-$(CONFIG_ARM_BRCMSTB_AVS_CPUFREQ)	+= brcmstb-avs-cpufreq.o
+obj-$(CONFIG_ARM_BRCMSTB_CPUFREQ)	+= brcmstb-cpufreq.o
 obj-$(CONFIG_ARCH_DAVINCI)		+= davinci-cpufreq.o
 obj-$(CONFIG_UX500_SOC_DB8500)		+= dbx500-cpufreq.o
 obj-$(CONFIG_ARM_EXYNOS5440_CPUFREQ)	+= exynos5440-cpufreq.o
diff --git a/drivers/cpufreq/brcmstb-cpufreq.c b/drivers/cpufreq/brcmstb-cpufreq.c
new file mode 100644
index 0000000..419638a
--- /dev/null
+++ b/drivers/cpufreq/brcmstb-cpufreq.c
@@ -0,0 +1,407 @@ 
+/*
+ * CPU frequency scaling for Broadcom set top box SoCs
+ *
+ * Copyright (c) 2016 Broadcom
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation version 2.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warranty
+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/cpufreq.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/platform_device.h>
+
+#define BRCMSTB_CPUFREQ_PREFIX	"brcmstb"
+#define BRCMSTB_CPUFREQ_NAME	BRCMSTB_CPUFREQ_PREFIX "-cpufreq"
+
+/* We search for these compatible strings. */
+#define BRCMSTB_DT_CPU_CLK_CTRL	"brcm,brcmstb-cpu-clk-div"
+#define BRCMSTB_DT_MEMC_DDR	"brcm,brcmstb-memc-ddr"
+#define BRCM_AVS_CPU_DATA	"brcm,avs-cpu-data-mem"
+
+/* We also need a few clocks in device tree. These are node names. */
+#define BRCMSTB_CLK_MDIV_CH0	"cpu_mdiv_ch0"
+#define BRCMSTB_CLK_NDIV_INT	"cpu_ndiv_int"
+#define BRCMSTB_CLK_SW_SCB	"sw_scb"
+
+#define BRCMSTB_TBL_SAFE_MODE	BIT(0)
+#define BRCMSTB_REG_SAFE_MODE	BIT(4)
+
+/* This is as low as we'll go in the frequency table. */
+#define MIN_CPU_FREQ		(100 * 1000)	/* in kHz */
+
+struct private_data {
+	void __iomem *cpu_clk_ctrl_reg;
+	struct device *dev;
+};
+
+/* Count the active memory controllers in the system. */
+static int count_memory_controllers(void)
+{
+	struct device_node *np = NULL;
+	int i = 0;
+
+	do {
+		np = of_find_compatible_node(np, NULL, BRCMSTB_DT_MEMC_DDR);
+		if (of_device_is_available(np))
+			i++;
+		of_node_put(np);
+	} while (np);
+
+	return i;
+}
+
+static int get_frequencies(const struct cpufreq_policy *policy,
+			   unsigned int *vco_freq, unsigned int *cpu_freq,
+			   unsigned int *scb_freq)
+{
+	struct clk *cpu_ndiv_int, *sw_scb;
+
+	cpu_ndiv_int = __clk_lookup(BRCMSTB_CLK_NDIV_INT);
+	if (!cpu_ndiv_int)
+		return -ENODEV;
+
+	sw_scb = __clk_lookup(BRCMSTB_CLK_SW_SCB);
+	if (!sw_scb)
+		return -ENODEV;
+
+	/* return frequencies in kHz */
+	*vco_freq = clk_get_rate(cpu_ndiv_int) / 1000;
+	*cpu_freq = clk_get_rate(policy->clk) / 1000;
+	*scb_freq = clk_get_rate(sw_scb) / 1000;
+
+	return 0;
+}
+
+/*
+ * Safe mode: When set, the CPU's bus unit is being throttled. This is done to
+ * avoid buffer overflows when the CPU-to-bus-clock ratio is low.
+ *
+ * The formula as to what constitutes a low CPU-to-bus-clock ratio takes into
+ * account the number of memory controllers active in the system and the SCB
+ * frequency. More memory controllers means safe mode is required starting at
+ * higher frequencies.
+ *
+ * For 1 memory controller, cpu_freq/scb_freq must be greater than or equal to
+ * 2 to not require safe mode.
+ *
+ * For 2 or 3 memory controllers, cpu_freq/scb_freq must be greater than or
+ * equal 3 to not require safe mode.
+ */
+
+static int freq_requires_safe_mode(unsigned int cpu_freq, unsigned int scb_freq,
+				   int num_memc)
+{
+	unsigned int safe_ratio;
+
+	switch (num_memc) {
+	case 1:
+		safe_ratio = 2;
+		break;
+	case 2:
+	case 3:
+		safe_ratio = 3;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return ((cpu_freq / scb_freq) < safe_ratio);
+}
+
+static struct cpufreq_frequency_table *
+brcmstb_get_freq_table(const struct cpufreq_policy *policy)
+{
+	unsigned int cpu_freq, vco_freq, scb_freq, mdiv, init_mdiv, f;
+	struct cpufreq_frequency_table *table;
+	struct private_data *priv;
+	int num_memc, ret;
+	unsigned int i = 0;
+
+	ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
+	if (ret)
+		return ERR_PTR(ret);
+
+	priv = policy->driver_data;
+	num_memc = count_memory_controllers();
+
+	/* Calculate the initial mdiv value. We'll increment mdiv from here. */
+	init_mdiv = vco_freq / cpu_freq;
+
+	/* Count how many frequencies we'll offer. */
+	f = cpu_freq;
+	for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
+		/* We only want to use "whole" MHz. */
+		if ((f % 1000) == 0)
+			i++;
+	}
+
+	table = devm_kzalloc(priv->dev, (i + 1) * sizeof(*table), GFP_KERNEL);
+	if (!table)
+		return ERR_PTR(-ENOMEM);
+
+	/* Now, fill the table. */
+	f = cpu_freq;
+	i = 0;
+	for (mdiv = init_mdiv; f >= MIN_CPU_FREQ; mdiv++, f = vco_freq / mdiv) {
+		if ((f % 1000) == 0) {
+			table[i].frequency = f;
+			ret = freq_requires_safe_mode(f, scb_freq, num_memc);
+			if (ret < 0)
+				return ERR_PTR(ret);
+			if (ret > 0)
+				table[i].driver_data |= BRCMSTB_TBL_SAFE_MODE;
+			i++;
+		}
+	}
+	table[i].frequency = CPUFREQ_TABLE_END;
+
+	return table;
+}
+
+static unsigned int brcmstb_cpufreq_get(unsigned int cpu)
+{
+	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
+
+	return clk_get_rate(policy->clk) / 1000;
+}
+
+static int brcmstb_target_index(struct cpufreq_policy *policy,
+				unsigned int index)
+{
+	struct cpufreq_frequency_table *entry;
+	struct private_data *priv;
+	int ret, safe_mode_needed;
+	u32 reg;
+
+	priv = policy->driver_data;
+	entry = &policy->freq_table[index];
+	safe_mode_needed = entry->driver_data & BRCMSTB_TBL_SAFE_MODE;
+
+	reg = readl(priv->cpu_clk_ctrl_reg);
+	if (safe_mode_needed && !(reg & BRCMSTB_REG_SAFE_MODE)) {
+		reg |= BRCMSTB_REG_SAFE_MODE;
+		writel(reg, priv->cpu_clk_ctrl_reg);
+	}
+	ret = clk_set_rate(policy->clk, entry->frequency * 1000);
+	if (!ret && !safe_mode_needed && (reg & BRCMSTB_REG_SAFE_MODE)) {
+		reg &= ~BRCMSTB_REG_SAFE_MODE;
+		writel(reg, priv->cpu_clk_ctrl_reg);
+	}
+
+	return ret;
+}
+
+/*
+ * All initialization code that we only want to execute once goes here. Setup
+ * code that can be re-tried on every core (if it failed before) can go into
+ * brcm_avs_cpufreq_init().
+ */
+static int brcmstb_prepare_init(struct platform_device *pdev)
+{
+	struct private_data *priv;
+	struct resource *res;
+	struct device *dev;
+
+	/*
+	 * If the BRCM STB AVS CPUfreq driver is supported, we bail, so that
+	 * the more modern approach implementing DVFS in firmware can be used.
+	 */
+	if (IS_ENABLED(CONFIG_ARM_BRCM_AVS_CPUFREQ)) {
+		struct device_node *np;
+
+		np = of_find_compatible_node(NULL, NULL, BRCM_AVS_CPU_DATA);
+		if (np) {
+			of_node_put(np);
+			return -ENXIO;
+		}
+	}
+
+	dev = &pdev->dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	priv->cpu_clk_ctrl_reg = devm_ioremap_resource(dev, res);
+	if (IS_ERR(priv->cpu_clk_ctrl_reg)) {
+		dev_err(dev, "couldn't map DT entry %s\n",
+			BRCMSTB_DT_CPU_CLK_CTRL);
+		return -ENODEV;
+	}
+
+	priv->dev = dev;
+	platform_set_drvdata(pdev, priv);
+
+	return 0;
+}
+
+static int brcmstb_cpu_init(struct cpufreq_policy *policy)
+{
+	struct cpufreq_frequency_table *freq_table;
+	struct platform_device *pdev;
+	struct private_data *priv;
+	struct clk *cpu_mdiv_ch0;
+	struct device *dev;
+	int ret;
+
+	cpu_mdiv_ch0 = __clk_lookup(BRCMSTB_CLK_MDIV_CH0);
+	if (!cpu_mdiv_ch0)
+		return -ENODEV;
+
+	pdev = cpufreq_get_driver_data();
+	priv = platform_get_drvdata(pdev);
+	dev = &pdev->dev;
+
+	policy->clk = cpu_mdiv_ch0;
+	policy->driver_data = priv;
+
+	freq_table = brcmstb_get_freq_table(policy);
+	if (IS_ERR(freq_table)) {
+		ret = PTR_ERR(freq_table);
+		dev_err(dev, "Couldn't determine frequency table (%d).\n", ret);
+		if (ret == -EINVAL)
+			dev_emerg(dev,
+				"Invalid number of memory controllers -- %d!\n",
+				count_memory_controllers());
+		return ret;
+	}
+
+	ret = cpufreq_table_validate_and_show(policy, freq_table);
+	if (ret) {
+		dev_err(dev, "invalid frequency table: %d\n", ret);
+		return ret;
+	}
+
+	dev_info(dev, "registered\n");
+
+	/* All cores share the same clock and thus the same policy. */
+	cpumask_setall(policy->cpus);
+
+	/* We start at the first entry in the frequency table. */
+	policy->cur = freq_table[0].frequency;
+
+	return 0;
+}
+
+/* Shows the number of memory controllers. */
+static ssize_t show_brcmstb_num_memc(struct cpufreq_policy *policy, char *buf)
+{
+	return sprintf(buf, "%u\n", count_memory_controllers());
+}
+
+/* Shows vco_freq, cpu_freq, and scb_freq in kHz. */
+static ssize_t show_brcmstb_freqs(struct cpufreq_policy *policy, char *buf)
+{
+	unsigned int vco_freq, cpu_freq, scb_freq;
+	int ret;
+
+	ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
+	if (ret)
+		return sprintf(buf, "<unknown>\n");
+
+	return sprintf(buf, "%u %u %u\n", vco_freq, cpu_freq, scb_freq);
+}
+
+/* Shows the lowest frequency (in kHz) that can be used without "safe mode". */
+static ssize_t show_brcmstb_safe_freq(struct cpufreq_policy *policy, char *buf)
+{
+	unsigned int vco_freq, cpu_freq, scb_freq;
+	unsigned int safe_freq = 0;
+	int i, num_memc, ret;
+
+	ret = get_frequencies(policy, &vco_freq, &cpu_freq, &scb_freq);
+	if (ret)
+		return sprintf(buf, "<unknown>\n");
+
+	num_memc = count_memory_controllers();
+
+	for (i = 0; policy->freq_table[i].frequency != CPUFREQ_TABLE_END; i++) {
+		ret = freq_requires_safe_mode(policy->freq_table[i].frequency,
+					      scb_freq, num_memc);
+		if (ret < 0)
+			return sprintf(buf, "<error> (%d)\n", ret);
+		if (ret == 0)
+			safe_freq = policy->freq_table[i].frequency;
+	}
+
+	return sprintf(buf, "%u\n", safe_freq);
+}
+
+cpufreq_freq_attr_ro(brcmstb_num_memc);
+cpufreq_freq_attr_ro(brcmstb_freqs);
+cpufreq_freq_attr_ro(brcmstb_safe_freq);
+
+static struct freq_attr *brcmstb_cpufreq_attr[] = {
+	&cpufreq_freq_attr_scaling_available_freqs,
+	&brcmstb_num_memc,
+	&brcmstb_freqs,
+	&brcmstb_safe_freq,
+	NULL
+};
+
+static struct cpufreq_driver brcmstb_driver = {
+	.flags		= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
+	.verify		= cpufreq_generic_frequency_table_verify,
+	.target_index	= brcmstb_target_index,
+	.get		= brcmstb_cpufreq_get,
+	.init		= brcmstb_cpu_init,
+	.attr		= brcmstb_cpufreq_attr,
+	.name		= BRCMSTB_CPUFREQ_PREFIX,
+};
+
+static int brcmstb_cpufreq_probe(struct platform_device *pdev)
+{
+	int ret;
+
+	ret = brcmstb_prepare_init(pdev);
+	if (ret)
+		return ret;
+
+	brcmstb_driver.driver_data = pdev;
+
+	return cpufreq_register_driver(&brcmstb_driver);
+}
+
+static int brcmstb_cpufreq_remove(struct platform_device *pdev)
+{
+	int ret;
+
+	ret = cpufreq_unregister_driver(&brcmstb_driver);
+	if (ret)
+		return ret;
+
+	platform_set_drvdata(pdev, NULL);
+
+	return 0;
+}
+
+static const struct of_device_id brcmstb_cpufreq_match[] = {
+	{ .compatible = BRCMSTB_DT_CPU_CLK_CTRL },
+	{ }
+};
+MODULE_DEVICE_TABLE(platform, brcmstb_cpufreq_match);
+
+static struct platform_driver brcmstb_cpufreq_platdrv = {
+	.driver = {
+		.name	= BRCMSTB_CPUFREQ_NAME,
+		.of_match_table = brcmstb_cpufreq_match,
+	},
+	.probe		= brcmstb_cpufreq_probe,
+	.remove		= brcmstb_cpufreq_remove,
+};
+module_platform_driver(brcmstb_cpufreq_platdrv);
+
+MODULE_AUTHOR("Markus Mayer <mmayer@broadcom.com>");
+MODULE_DESCRIPTION("CPUfreq driver for Broadcom STB SoCs");
+MODULE_LICENSE("GPL");