diff mbox series

[2/4] pwm: Add Apple PWM controller

Message ID 20221028165215.43662-3-fnkl.kernel@gmail.com (mailing list archive)
State New, archived
Headers show
Series PWM and keyboard backlight driver for ARM Macs | expand

Commit Message

Sasha Finkelstein Oct. 28, 2022, 4:52 p.m. UTC 
Adds the Apple PWM controller driver.

Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
---
 drivers/pwm/Kconfig     |  12 ++++
 drivers/pwm/Makefile    |   1 +
 drivers/pwm/pwm-apple.c | 124 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 137 insertions(+)
 create mode 100644 drivers/pwm/pwm-apple.c

Comments

Krzysztof Kozlowski Oct. 28, 2022, 5:54 p.m. UTC | #1 
On 28/10/2022 12:52, Sasha Finkelstein wrote:
> Adds the Apple PWM controller driver.
> 
> Signed-off-by: Sasha Finkelstein <fnkl.kernel@gmail.com>
> ---
>  drivers/pwm/Kconfig     |  12 ++++
>  drivers/pwm/Makefile    |   1 +
>  drivers/pwm/pwm-apple.c | 124 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 137 insertions(+)
>  create mode 100644 drivers/pwm/pwm-apple.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 60d13a949bc5..ec6acb368073 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -51,6 +51,18 @@ config PWM_AB8500
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-ab8500.
>  
> +config PWM_APPLE
> +	tristate "Apple SoC PWM support"
> +	depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)

Why this code cannot be build on 32-bit?

> +	help
> +	  Generic PWM framework driver for PWM controller present on
> +	  Apple SoCs
> +

Best regards,
Krzysztof
Sasha Finkelstein Oct. 28, 2022, 6:51 p.m. UTC | #2 
On Fri, 28 Oct 2022 at 20:54, Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 28/10/2022 12:52, Sasha Finkelstein wrote:
> > +config PWM_APPLE
> > +     tristate "Apple SoC PWM support"
> > +     depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
>
> Why this code cannot be build on 32-bit?
It uses 64-bit divisions, which causes it to fail to build on 32-bit
mips. It should not be a
problem, since this hardware is only present on 64-bit SoCs.
Krzysztof Kozlowski Oct. 28, 2022, 7:49 p.m. UTC | #3 
On 28/10/2022 14:51, Sasha Finkelstein wrote:
> On Fri, 28 Oct 2022 at 20:54, Krzysztof Kozlowski
> <krzysztof.kozlowski@linaro.org> wrote:
>>
>> On 28/10/2022 12:52, Sasha Finkelstein wrote:
>>> +config PWM_APPLE
>>> +     tristate "Apple SoC PWM support"
>>> +     depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
>>
>> Why this code cannot be build on 32-bit?
> It uses 64-bit divisions, which causes it to fail to build on 32-bit
> mips. It should not be a
> problem, since this hardware is only present on 64-bit SoCs.

Does not matter, code should be portable and buildable on 32-bit. If it
does not build then your code is not correct.

You need to investigate the failure. Maybe using do_div would solve (or
other macros from div64.h)

Best regards,
Krzysztof
Hector Martin Oct. 29, 2022, 6:25 a.m. UTC | #4 
On 29/10/2022 04.49, Krzysztof Kozlowski wrote:
> On 28/10/2022 14:51, Sasha Finkelstein wrote:
>> On Fri, 28 Oct 2022 at 20:54, Krzysztof Kozlowski
>> <krzysztof.kozlowski@linaro.org> wrote:
>>>
>>> On 28/10/2022 12:52, Sasha Finkelstein wrote:
>>>> +config PWM_APPLE
>>>> +     tristate "Apple SoC PWM support"
>>>> +     depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
>>>
>>> Why this code cannot be build on 32-bit?
>> It uses 64-bit divisions, which causes it to fail to build on 32-bit
>> mips. It should not be a
>> problem, since this hardware is only present on 64-bit SoCs.
> 
> Does not matter, code should be portable and buildable on 32-bit. If it
> does not build then your code is not correct.

This statement does not apply in general. There are plenty of drivers
which cannot reasonably build for 32-bit, and make no sense because no
32-bit hardware exists that could use them. Examples include anything
that accesses 64-bit registers on 64-bit SoCs the normal way, and
further anything that touches CPU stuff like system registers.

In *this* case, if the only issue is some 64-bit math, then yes, it
should be made to build on 32-bit (especially since this is likely to
also work for older 32-bit Apple SoCs). But the (COMPILE_TEST && 64BIT)
pattern is definitely valid in other cases, and I've been adding it
lately to shut up the kernel test bot since it makes no sense to compile
test a whole pile of our drivers on 32-bit architectures - they
fundamentally can't compile without adding pointless hypothetical broken
fluff to the driver like split MMIO accesses (which often can't work on
real hardware), and it serves no purpose.


- Hector
diff mbox series

Patch

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 60d13a949bc5..ec6acb368073 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -51,6 +51,18 @@  config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_APPLE
+	tristate "Apple SoC PWM support"
+	depends on ARCH_APPLE || (COMPILE_TEST && 64BIT)
+	help
+	  Generic PWM framework driver for PWM controller present on
+	  Apple SoCs
+
+	  Say Y here if you have an ARM Apple laptop, otherwise say N
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-apple.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on ARCH_AT91 || COMPILE_TEST
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index 7bf1a29f02b8..19899b912e00 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -2,6 +2,7 @@ 
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(CONFIG_PWM_APPLE)		+= pwm-apple.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
diff --git a/drivers/pwm/pwm-apple.c b/drivers/pwm/pwm-apple.c
new file mode 100644
index 000000000000..4cfa9bf435dc
--- /dev/null
+++ b/drivers/pwm/pwm-apple.c
@@ -0,0 +1,124 @@ 
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Driver for the Apple SoC PWM controller
+ *
+ * Copyright The Asahi Linux Contributors
+ */
+
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+#include <linux/io.h>
+#include <linux/clk.h>
+#include <linux/pm_runtime.h>
+
+#define PWM_CONTROL     0x00
+#define PWM_ON_CYCLES   0x1c
+#define PWM_OFF_CYCLES  0x18
+
+#define CTRL_ENABLE        BIT(0)
+#define CTRL_MODE          BIT(2)
+#define CTRL_UPDATE        BIT(5)
+#define CTRL_TRIGGER       BIT(9)
+#define CTRL_INVERT        BIT(10)
+#define CTRL_OUTPUT_ENABLE BIT(14)
+
+struct apple_pwm {
+	struct pwm_chip chip;
+	void __iomem *base;
+	u64 clkrate;
+};
+
+static int apple_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			   const struct pwm_state *state)
+{
+	struct apple_pwm *fpwm;
+	u64 on_cycles, off_cycles;
+
+	fpwm = container_of(chip, struct apple_pwm, chip);
+	if (state->enabled) {
+		on_cycles = fpwm->clkrate * state->duty_cycle / NSEC_PER_SEC;
+		off_cycles = (fpwm->clkrate * state->period / NSEC_PER_SEC) - on_cycles;
+		writel(on_cycles, fpwm->base + PWM_ON_CYCLES);
+		writel(off_cycles, fpwm->base + PWM_OFF_CYCLES);
+		writel(CTRL_ENABLE | CTRL_OUTPUT_ENABLE | CTRL_UPDATE,
+		       fpwm->base + PWM_CONTROL);
+	} else {
+		writel(0, fpwm->base + PWM_CONTROL);
+	}
+	return 0;
+}
+
+static void apple_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+			   struct pwm_state *state)
+{
+	struct apple_pwm *fpwm;
+	u32 on_cycles, off_cycles, ctrl;
+
+	fpwm = container_of(chip, struct apple_pwm, chip);
+
+	ctrl = readl(fpwm->base + PWM_CONTROL);
+	on_cycles = readl(fpwm->base + PWM_ON_CYCLES);
+	off_cycles = readl(fpwm->base + PWM_OFF_CYCLES);
+
+	state->enabled = (ctrl & CTRL_ENABLE) && (ctrl & CTRL_OUTPUT_ENABLE);
+	state->polarity = PWM_POLARITY_NORMAL;
+	state->duty_cycle = on_cycles / fpwm->clkrate * NSEC_PER_SEC;
+	state->period = (off_cycles + on_cycles) / fpwm->clkrate * NSEC_PER_SEC;
+}
+
+static const struct pwm_ops apple_pwm_ops = {
+	.apply = apple_pwm_apply,
+	.get_state = apple_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int apple_pwm_probe(struct platform_device *pdev)
+{
+	struct apple_pwm *pwm;
+	struct clk *clk;
+	int ret;
+
+	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+
+	pwm->base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(pwm->base))
+		return PTR_ERR(pwm->base);
+
+	platform_set_drvdata(pdev, pwm);
+
+	clk = devm_clk_get_enabled(&pdev->dev, NULL);
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	pwm->clkrate = clk_get_rate(clk);
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.npwm = 1;
+	pwm->chip.ops = &apple_pwm_ops;
+
+	ret = devm_pwmchip_add(&pdev->dev, &pwm->chip);
+	return ret;
+}
+
+static const struct of_device_id apple_pwm_of_match[] = {
+	{ .compatible = "apple,s5l-fpwm" },
+	{}
+};
+MODULE_DEVICE_TABLE(of, apple_pwm_of_match);
+
+static struct platform_driver apple_pwm_driver = {
+	.probe = apple_pwm_probe,
+	.driver = {
+		.name = "apple-pwm",
+		.owner = THIS_MODULE,
+		.of_match_table = apple_pwm_of_match,
+	},
+};
+module_platform_driver(apple_pwm_driver);
+
+MODULE_DESCRIPTION("Apple SoC PWM driver");
+MODULE_LICENSE("Dual MIT/GPL");