[resend rfc v4]pwm: add BCM2835 PWM driver

[resend rfc v4]pwm: add BCM2835 PWM driver

[Bart Tanghe]

Add pwm driver for Broadcom BCM2835 processor (Raspberry Pi) 
Signed-off-by: Bart Tanghe <bart.tanghe@thomasmore.be>
---
Changes in v4:
 - add the second pwm channel (tested on raspberry pi B+)
 - add the code and code style recommendations

diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
new file mode 100644
index 0000000..0a0c84e
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt
@@ -0,0 +1,13 @@
+BCM2835 PWM controller (Raspberry Pi controller)
+
+Required properties:
+- compatible: should be "brcm,bcm2835-pwm"
+- reg: physical base address and length of the controller's registers
+
+Examples:
+
+pwm@2020c000 {
+	compatible = "bcrm,bcm2835-pwm";
+	reg = <0x2020c000 0x28>;
+	clocks = <&clk_pwm>;
+};
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 22f2f28..a277256 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -62,6 +62,15 @@ config PWM_ATMEL_TCB
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-atmel-tcb.
 
+config PWM_BCM2835
+	tristate "BCM2835 PWM support"
+	depends on MACH_BCM2835 || MACH_BCM2708
+	help
+	  PWM framework driver for BCM2835 controller (Raspberry Pi)
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-bcm2835.
+
 config PWM_BFIN
 	tristate "Blackfin PWM support"
 	depends on BFIN_GPTIMERS
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index d8906ec..9863590 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
+obj-$(CONFIG_PWM_BCM2835)	+= pwm-bcm2835.o
 obj-$(CONFIG_PWM_BFIN)		+= pwm-bfin.o
 obj-$(CONFIG_PWM_EP93XX)	+= pwm-ep93xx.o
 obj-$(CONFIG_PWM_IMX)		+= pwm-imx.o
diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c
new file mode 100644
index 0000000..50a079d
--- /dev/null
+++ b/drivers/pwm/pwm-bcm2835.c
@@ -0,0 +1,198 @@
+/*
+ * Copyright (C) 2014 Thomas more
+ *
+ * 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.
+ */
+
+#include <linux/clk.h>
+#include <linux/err.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/pwm.h>
+
+#define DUTY		0x14
+#define PERIOD		0x10
+#define CHANNEL		0x10
+
+#define PWM_ENABLE	(1 << 0)
+#define PWM_POLARITY	(1 << 4)
+
+#define PWM_CONTROL_MASK	0xff
+#define PWM_CONTROL_ENABLE	0x80
+#define PWM_CONTROL_DISABLE	0xff
+#define MIN_PERIOD		108		/* 9.2Mhz max pwm clock */
+
+struct bcm2835_pwm {
+	struct pwm_chip chip;
+	struct device *dev;
+	int channel;
+	unsigned long scaler;
+	void __iomem *base;
+	struct clk *clk;
+};
+
+static inline struct bcm2835_pwm  *to_bcm2835_pwm(struct pwm_chip *chip)
+{
+	return container_of(chip, struct bcm2835_pwm, chip);
+}
+
+static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+	u32 value;
+
+	value = readl(pc->base) & ~(PWM_CONTROL_MASK << 8 * pwm->pwm);
+	value |= (PWM_CONTROL_ENABLE << (8 * pwm->pwm));
+	writel(value, pc->base);
+	return 0;
+}
+
+static void bcm2835_pwm_free(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+	u32 value;
+
+	value = readl(pc->base) & ~(PWM_CONTROL_MASK << 8 * pwm->pwm);
+	value &= (~PWM_CONTROL_DISABLE << (8 * pwm->pwm));
+	writel(value, pc->base);
+}
+
+static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
+			      int duty_ns, int period_ns)
+{
+	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+
+	if (period_ns > MIN_PERIOD) {
+		writel(duty_ns / pc->scaler,
+			 pc->base + DUTY + pwm->pwm * CHANNEL);
+		writel(period_ns / pc->scaler,
+			pc->base + PERIOD + pwm->pwm * CHANNEL);
+	} else {
+		dev_err(pc->dev, "Period not supported\n");
+	}
+
+	return 0;
+}
+
+static int bcm2835_pwm_enable(struct pwm_chip *chip,
+			      struct pwm_device *pwm)
+{
+	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+	u32 value;
+
+	value = readl(pc->base);
+	value |= (PWM_ENABLE << (8 * pwm->pwm));
+	writel(value, pc->base);
+	return 0;
+}
+
+static void bcm2835_pwm_disable(struct pwm_chip *chip,
+				struct pwm_device *pwm)
+{
+	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+	u32 value;
+
+	value = readl(pc->base);
+	value &= ~(PWM_ENABLE << (8 * pwm->pwm));
+	writel(value, pc->base);
+}
+
+static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
+				enum pwm_polarity polarity)
+{
+	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
+	u32 value;
+
+	if (polarity == PWM_POLARITY_NORMAL) {
+		value = readl(pc->base);
+		value &= ~(PWM_POLARITY << 8 * pwm->pwm);
+		writel(value, pc->base);
+	} else if (polarity == PWM_POLARITY_INVERSED) {
+		value = readl(pc->base);
+		value |= PWM_POLARITY << (8 * pwm->pwm);
+		writel(value, pc->base);
+	}
+	return 0;
+}
+
+static const struct pwm_ops bcm2835_pwm_ops = {
+	.request = bcm2835_pwm_request,
+	.free = bcm2835_pwm_free,
+	.config = bcm2835_pwm_config,
+	.enable = bcm2835_pwm_enable,
+	.disable = bcm2835_pwm_disable,
+	.set_polarity = bcm2835_set_polarity,
+	.owner = THIS_MODULE,
+};
+
+static int bcm2835_pwm_probe(struct platform_device *pdev)
+{
+	struct bcm2835_pwm *pwm;
+	int ret;
+	struct resource *r;
+	struct clk *clk;
+
+	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
+	if (!pwm)
+		return -ENOMEM;
+
+	pwm->dev = &pdev->dev;
+
+	clk = clk_get(&pdev->dev, NULL);
+	if (IS_ERR(clk)) {
+		dev_err(&pdev->dev, "no clock found: %ld\n", PTR_ERR(clk));
+		return PTR_ERR(clk);
+	}
+
+	pwm->clk = clk;
+	clk_prepare_enable(pwm->clk);
+	pwm->scaler = NSEC_PER_SEC / clk_get_rate(clk);
+
+	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	pwm->base = devm_ioremap_resource(&pdev->dev, r);
+	if (IS_ERR(pwm->base))
+		return PTR_ERR(pwm->base);
+
+	pwm->chip.dev = &pdev->dev;
+	pwm->chip.ops = &bcm2835_pwm_ops;
+	pwm->chip.npwm = 2;
+
+	ret = pwmchip_add(&pwm->chip);
+	if (ret < 0) {
+		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
+		return -1;
+	}
+	platform_set_drvdata(pdev, pwm);
+	return 0;
+}
+
+static int bcm2835_pwm_remove(struct platform_device *pdev)
+{
+	struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
+	clk_disable_unprepare(pc->clk);
+	return pwmchip_remove(&pc->chip);
+}
+
+static const struct of_device_id bcm2835_pwm_of_match[] = {
+	{ .compatible = "brcm,bcm2835-pwm", },
+	{ /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
+
+static struct platform_driver bcm2835_pwm_driver = {
+	.driver = {
+		.name = "bcm2835-pwm",
+		.of_match_table = bcm2835_pwm_of_match,
+	},
+	.probe = bcm2835_pwm_probe,
+	.remove = bcm2835_pwm_remove,
+};
+module_platform_driver(bcm2835_pwm_driver);
+
+MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be");
+MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
+MODULE_LICENSE("GPL v2");

Re: [resend rfc v4]pwm: add BCM2835 PWM driver

[Marc Kleine-Budde]

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On 09/29/2014 04:40 PM, Bart Tanghe wrote:
> +static int bcm2835_pwm_probe(struct platform_device *pdev)
> +{
> +	struct bcm2835_pwm *pwm;
> +	int ret;
> +	struct resource *r;
> +	struct clk *clk;
> +
> +	pwm = devm_kzalloc(&pdev->dev, sizeof(*pwm), GFP_KERNEL);
> +	if (!pwm)
> +		return -ENOMEM;
> +
> +	pwm->dev = &pdev->dev;
> +
> +	clk = clk_get(&pdev->dev, NULL);

Better use devm_, as you don't free the clock in case of an error and
during remove()

> +	if (IS_ERR(clk)) {
> +		dev_err(&pdev->dev, "no clock found: %ld\n", PTR_ERR(clk));
> +		return PTR_ERR(clk);
> +	}
> +
> +	pwm->clk = clk;
> +	clk_prepare_enable(pwm->clk);

Please check the return value of clk_prepare_enable()

> +	pwm->scaler = NSEC_PER_SEC / clk_get_rate(clk);
> +
> +	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	pwm->base = devm_ioremap_resource(&pdev->dev, r);
> +	if (IS_ERR(pwm->base))
> +		return PTR_ERR(pwm->base);
> +
> +	pwm->chip.dev = &pdev->dev;
> +	pwm->chip.ops = &bcm2835_pwm_ops;
> +	pwm->chip.npwm = 2;
> +
> +	ret = pwmchip_add(&pwm->chip);
> +	if (ret < 0) {
> +		dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
> +		return -1;

Please propagate the error vlaue:

    return ret;

> +	}
> +	platform_set_drvdata(pdev, pwm);

Better do this before pwmchip_add()

> +	return 0;
> +}
> +
> +static int bcm2835_pwm_remove(struct platform_device *pdev)
> +{
> +	struct bcm2835_pwm *pc = platform_get_drvdata(pdev);
> +	clk_disable_unprepare(pc->clk);
> +	return pwmchip_remove(&pc->chip);
> +}
> +
> +static const struct of_device_id bcm2835_pwm_of_match[] = {
> +	{ .compatible = "brcm,bcm2835-pwm", },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, bcm2835_pwm_of_match);
> +
> +static struct platform_driver bcm2835_pwm_driver = {
> +	.driver = {
> +		.name = "bcm2835-pwm",
> +		.of_match_table = bcm2835_pwm_of_match,
> +	},
> +	.probe = bcm2835_pwm_probe,
> +	.remove = bcm2835_pwm_remove,
> +};
> +module_platform_driver(bcm2835_pwm_driver);
> +
> +MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be");
> +MODULE_DESCRIPTION("Broadcom BCM2835 PWM driver");
> +MODULE_LICENSE("GPL v2");

regards,
Marc

-- 
Pengutronix e.K.                  | Marc Kleine-Budde           |
Industrial Linux Solutions        | Phone: +49-231-2826-924     |
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Re: [resend rfc v4]pwm: add BCM2835 PWM driver

[Stephen Warren]

On 09/29/2014 08:40 AM, Bart Tanghe wrote:
> Add pwm driver for Broadcom BCM2835 processor (Raspberry Pi) 
> Signed-off-by: Bart Tanghe <bart.tanghe@thomasmore.be>

There needs to be a blank line between the description and the tags.

> diff --git a/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt b/Documentation/devicetree/bindings/pwm/pwm-bcm2835.txt

> +Required properties:
> +- compatible: should be "brcm,bcm2835-pwm"
> +- reg: physical base address and length of the controller's registers

This needs to document the clock property too.

It'd be nice to require clock-names rather than doing clock lookup by
index, but I suppose it's not too much of a problem with this device.

> diff --git a/drivers/pwm/pwm-bcm2835.c b/drivers/pwm/pwm-bcm2835.c

> +/*
> + * Copyright (C) 2014 Thomas more

But the git commit doesn't have "Thomas More" as the author, nor Thomas'
Signed-off-by line. Can you explain the history of this code?

> +static int bcm2835_pwm_request(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> +	u32 value;
> +
> +	value = readl(pc->base) & ~(PWM_CONTROL_MASK << 8 * pwm->pwm);
> +	value |= (PWM_CONTROL_ENABLE << (8 * pwm->pwm));

It'd be nice to use a #define rather than hard-coded "8" here. Perhaps:

#define PWM_CONTROL_STRIDE 8

Why does _request() enable the PWM output; shouldn't that be deferred
until _enable()? _free() might not want to disable the output, if the
PWM core guarantees that _disable() is always called.

> +static int bcm2835_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm,
> +			      int duty_ns, int period_ns)
> +{
> +	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> +
> +	if (period_ns > MIN_PERIOD) {
> +		writel(duty_ns / pc->scaler,
> +			 pc->base + DUTY + pwm->pwm * CHANNEL);
> +		writel(period_ns / pc->scaler,
> +			pc->base + PERIOD + pwm->pwm * CHANNEL);
> +	} else {
> +		dev_err(pc->dev, "Period not supported\n");
> +	}

The "else" case should propagate the error. It'd be better to do the
error-checking first to remove an indent level from the rest of the code:

	if (period_ns <= MIN_PERIOD) {
		dev_err(...);
		return -EINVAL;
	}
	writel(...);

> +static int bcm2835_set_polarity(struct pwm_chip *chip, struct pwm_device *pwm,
> +				enum pwm_polarity polarity)
> +{
> +	struct bcm2835_pwm *pc = to_bcm2835_pwm(chip);
> +	u32 value;
> +
> +	if (polarity == PWM_POLARITY_NORMAL) {
> +		value = readl(pc->base);
> +		value &= ~(PWM_POLARITY << 8 * pwm->pwm);
> +		writel(value, pc->base);
> +	} else if (polarity == PWM_POLARITY_INVERSED) {
> +		value = readl(pc->base);
> +		value |= PWM_POLARITY << (8 * pwm->pwm);
> +		writel(value, pc->base);
> +	}

If you move the readl/writel outside the if statement, you remove the
duplication of code.

> +static const struct pwm_ops bcm2835_pwm_ops = {
...
> +	.owner = THIS_MODULE,
> +};

Doesn't something in the driver core automatically set .owner now?
Perhaps that's only for certain subsystems though?

> +MODULE_AUTHOR("Bart Tanghe <bart.tanghe@thomasmore.be");

That doesn't match the (c) message at the start of the file.