Re: [PATCH v7 11/11] pwm: Add Raspberry Pi Firmware based PWM bus

[Nicolas Saenz Julienne]

On Mon, 2021-01-18 at 13:32 +0100, Nicolas Saenz Julienne wrote:
> Adds support to control the PWM bus available in official Raspberry Pi
> PoE HAT. Only RPi's co-processor has access to it, so commands have to
> be sent through RPi's firmware mailbox interface.
> 
> Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> 
> ---

ping :)

> Changes since v6:
> - Use %pe
> - Round divisions properly
> - Use dev_err_probe()
> - Pass check_patch
> 
> Changes since v3:
>  - Rename compatible string to be more explicit WRT to bus's limitations
> 
> Changes since v2:
>  - Use devm_rpi_firmware_get()
>  - Rename driver
>  - Small cleanups
> 
> Changes since v1:
>  - Use default pwm bindings and get rid of xlate() function
>  - Correct spelling errors
>  - Correct apply() function
>  - Round values
>  - Fix divisions in arm32 mode
>  - Small cleanups
> 
>  drivers/pwm/Kconfig               |   9 ++
>  drivers/pwm/Makefile              |   1 +
>  drivers/pwm/pwm-raspberrypi-poe.c | 220 ++++++++++++++++++++++++++++++
>  3 files changed, 230 insertions(+)
>  create mode 100644 drivers/pwm/pwm-raspberrypi-poe.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 0937e1c047ac..75e2344703b3 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -423,6 +423,15 @@ config PWM_PXA
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-pxa.
>  
> 
> +config PWM_RASPBERRYPI_POE
> +	tristate "Raspberry Pi Firwmware PoE Hat PWM support"
> +	# Make sure not 'y' when RASPBERRYPI_FIRMWARE is 'm'. This can only
> +	# happen when COMPILE_TEST=y, hence the added !RASPBERRYPI_FIRMWARE.
> +	depends on RASPBERRYPI_FIRMWARE || (COMPILE_TEST && !RASPBERRYPI_FIRMWARE)
> +	help
> +	  Enable Raspberry Pi firmware controller PWM bus used to control the
> +	  official RPI PoE hat
> +
>  config PWM_RCAR
>  	tristate "Renesas R-Car PWM support"
>  	depends on ARCH_RENESAS || COMPILE_TEST
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index 18b89d7fd092..ed28d7bd4c64 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -38,6 +38,7 @@ obj-$(CONFIG_PWM_MXS)		+= pwm-mxs.o
>  obj-$(CONFIG_PWM_OMAP_DMTIMER)	+= pwm-omap-dmtimer.o
>  obj-$(CONFIG_PWM_PCA9685)	+= pwm-pca9685.o
>  obj-$(CONFIG_PWM_PXA)		+= pwm-pxa.o
> +obj-$(CONFIG_PWM_RASPBERRYPI_POE)	+= pwm-raspberrypi-poe.o
>  obj-$(CONFIG_PWM_RCAR)		+= pwm-rcar.o
>  obj-$(CONFIG_PWM_RENESAS_TPU)	+= pwm-renesas-tpu.o
>  obj-$(CONFIG_PWM_ROCKCHIP)	+= pwm-rockchip.o
> diff --git a/drivers/pwm/pwm-raspberrypi-poe.c b/drivers/pwm/pwm-raspberrypi-poe.c
> new file mode 100644
> index 000000000000..ca845e8fabe6
> --- /dev/null
> +++ b/drivers/pwm/pwm-raspberrypi-poe.c
> @@ -0,0 +1,220 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2020 Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>
> + * For more information on Raspberry Pi's PoE hat see:
> + * https://www.raspberrypi.org/products/poe-hat/
> + *
> + * Limitations:
> + *  - No disable bit, so a disabled PWM is simulated by duty_cycle 0
> + *  - Only normal polarity
> + *  - Fixed 12.5 kHz period
> + *
> + * The current period is completed when HW is reconfigured.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>
> +
> +#include <soc/bcm2835/raspberrypi-firmware.h>
> +#include <dt-bindings/pwm/raspberrypi,firmware-poe-pwm.h>
> +
> +#define RPI_PWM_MAX_DUTY		255
> +#define RPI_PWM_PERIOD_NS		80000 /* 12.5 kHz */
> +
> +#define RPI_PWM_CUR_DUTY_REG		0x0
> +#define RPI_PWM_DEF_DUTY_REG		0x1
> +
> +struct raspberrypi_pwm {
> +	struct rpi_firmware *firmware;
> +	struct pwm_chip chip;
> +	unsigned int duty_cycle;
> +};
> +
> +struct raspberrypi_pwm_prop {
> +	__le32 reg;
> +	__le32 val;
> +	__le32 ret;
> +} __packed;
> +
> +static inline
> +struct raspberrypi_pwm *raspberrypi_pwm_from_chip(struct pwm_chip *chip)
> +{
> +	return container_of(chip, struct raspberrypi_pwm, chip);
> +}
> +
> +static int raspberrypi_pwm_set_property(struct rpi_firmware *firmware,
> +					u32 reg, u32 val)
> +{
> +	struct raspberrypi_pwm_prop msg = {
> +		.reg = cpu_to_le32(reg),
> +		.val = cpu_to_le32(val),
> +	};
> +	int ret;
> +
> +	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
> +				    &msg, sizeof(msg));
> +	if (ret)
> +		return ret;
> +	if (msg.ret)
> +		return -EIO;
> +
> +	return 0;
> +}
> +
> +static int raspberrypi_pwm_get_property(struct rpi_firmware *firmware,
> +					u32 reg, u32 *val)
> +{
> +	struct raspberrypi_pwm_prop msg = {
> +		.reg = reg
> +	};
> +	int ret;
> +
> +	ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
> +				    &msg, sizeof(msg));
> +	if (ret)
> +		return ret;
> +	if (msg.ret)
> +		return -EIO;
> +
> +	*val = le32_to_cpu(msg.val);
> +
> +	return 0;
> +}
> +
> +static void raspberrypi_pwm_get_state(struct pwm_chip *chip,
> +				      struct pwm_device *pwm,
> +				      struct pwm_state *state)
> +{
> +	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
> +
> +	state->period = RPI_PWM_PERIOD_NS;
> +	state->duty_cycle = DIV_ROUND_UP(rpipwm->duty_cycle * RPI_PWM_PERIOD_NS,
> +					 RPI_PWM_MAX_DUTY);
> +	state->enabled = !!(rpipwm->duty_cycle);
> +	state->polarity = PWM_POLARITY_NORMAL;
> +}
> +
> +static int raspberrypi_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +				 const struct pwm_state *state)
> +{
> +	struct raspberrypi_pwm *rpipwm = raspberrypi_pwm_from_chip(chip);
> +	unsigned int duty_cycle;
> +	int ret;
> +
> +	if (state->period < RPI_PWM_PERIOD_NS ||
> +	    state->polarity != PWM_POLARITY_NORMAL)
> +		return -EINVAL;
> +
> +	if (!state->enabled)
> +		duty_cycle = 0;
> +	else if (state->duty_cycle < RPI_PWM_PERIOD_NS)
> +		duty_cycle = DIV_ROUND_DOWN_ULL(state->duty_cycle * RPI_PWM_MAX_DUTY,
> +						RPI_PWM_PERIOD_NS);
> +	else
> +		duty_cycle = RPI_PWM_MAX_DUTY;
> +
> +	if (duty_cycle == rpipwm->duty_cycle)
> +		return 0;
> +
> +	ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
> +					   duty_cycle);
> +	if (ret) {
> +		dev_err(chip->dev, "Failed to set duty cycle: %pe\n",
> +			ERR_PTR(ret));
> +		return ret;
> +	}
> +
> +	/*
> +	 * This sets the default duty cycle after resetting the board, we
> +	 * updated it every time to mimic Raspberry Pi's downstream's driver
> +	 * behaviour.
> +	 */
> +	ret = raspberrypi_pwm_set_property(rpipwm->firmware, RPI_PWM_DEF_DUTY_REG,
> +					   duty_cycle);
> +	if (ret) {
> +		dev_err(chip->dev, "Failed to set default duty cycle: %pe\n",
> +			ERR_PTR(ret));
> +		return ret;
> +	}
> +
> +	rpipwm->duty_cycle = duty_cycle;
> +
> +	return 0;
> +}
> +
> +static const struct pwm_ops raspberrypi_pwm_ops = {
> +	.get_state = raspberrypi_pwm_get_state,
> +	.apply = raspberrypi_pwm_apply,
> +	.owner = THIS_MODULE,
> +};
> +
> +static int raspberrypi_pwm_probe(struct platform_device *pdev)
> +{
> +	struct device_node *firmware_node;
> +	struct device *dev = &pdev->dev;
> +	struct rpi_firmware *firmware;
> +	struct raspberrypi_pwm *rpipwm;
> +	int ret;
> +
> +	firmware_node = of_get_parent(dev->of_node);
> +	if (!firmware_node) {
> +		dev_err(dev, "Missing firmware node\n");
> +		return -ENOENT;
> +	}
> +
> +	firmware = devm_rpi_firmware_get(&pdev->dev, firmware_node);
> +	of_node_put(firmware_node);
> +	if (!firmware)
> +		return dev_err_probe(dev, -EPROBE_DEFER,
> +				     "Failed to get firmware handle\n");
> +
> +	rpipwm = devm_kzalloc(&pdev->dev, sizeof(*rpipwm), GFP_KERNEL);
> +	if (!rpipwm)
> +		return -ENOMEM;
> +
> +	rpipwm->firmware = firmware;
> +	rpipwm->chip.dev = dev;
> +	rpipwm->chip.ops = &raspberrypi_pwm_ops;
> +	rpipwm->chip.base = -1;
> +	rpipwm->chip.npwm = RASPBERRYPI_FIRMWARE_PWM_NUM;
> +
> +	platform_set_drvdata(pdev, rpipwm);
> +
> +	ret = raspberrypi_pwm_get_property(rpipwm->firmware, RPI_PWM_CUR_DUTY_REG,
> +					   &rpipwm->duty_cycle);
> +	if (ret) {
> +		dev_err(dev, "Failed to get duty cycle: %pe\n", ERR_PTR(ret));
> +		return ret;
> +	}
> +
> +	return pwmchip_add(&rpipwm->chip);
> +}
> +
> +static int raspberrypi_pwm_remove(struct platform_device *pdev)
> +{
> +	struct raspberrypi_pwm *rpipwm = platform_get_drvdata(pdev);
> +
> +	return pwmchip_remove(&rpipwm->chip);
> +}
> +
> +static const struct of_device_id raspberrypi_pwm_of_match[] = {
> +	{ .compatible = "raspberrypi,firmware-poe-pwm", },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
> +
> +static struct platform_driver raspberrypi_pwm_driver = {
> +	.driver = {
> +		.name = "raspberrypi-poe-pwm",
> +		.of_match_table = raspberrypi_pwm_of_match,
> +	},
> +	.probe = raspberrypi_pwm_probe,
> +	.remove = raspberrypi_pwm_remove,
> +};
> +module_platform_driver(raspberrypi_pwm_driver);
> +
> +MODULE_AUTHOR("Nicolas Saenz Julienne <nsaenzjulienne@xxxxxxx>");
> +MODULE_DESCRIPTION("Raspberry Pi Firmware Based PWM Bus Driver");
> +MODULE_LICENSE("GPL v2");

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