diff mbox series

[v2,10/10] pwm: Add Raspberry Pi Firmware based PWM bus

Message ID 20201022155858.20867-11-nsaenzjulienne@suse.de
State Superseded
Headers show
Series Raspberry Pi PoE HAT fan support | expand

Commit Message

Nicolas Saenz Julienne Oct. 22, 2020, 3:58 p.m. UTC
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@suse.de>

---

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
 - Add comment explaining weird Kconfig construct

 drivers/pwm/Kconfig           |   9 ++
 drivers/pwm/Makefile          |   1 +
 drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++++++++++++++++++
 3 files changed, 231 insertions(+)
 create mode 100644 drivers/pwm/pwm-raspberrypi.c

Comments

Andy Shevchenko Oct. 22, 2020, 6:53 p.m. UTC | #1
On Thu, Oct 22, 2020 at 9:05 PM Nicolas Saenz Julienne
<nsaenzjulienne@suse.de> 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.

>  drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++++++++++++++++++

Name is completely confusing.
Please, make it unique enough to understand that this is exactly the
device it serves for.

For example, pwm-rpi-poe is better.

...

> + *  - Only normal polarity

Can't it be emulated? Isn't it 100% - duty cycle % ?


> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/pwm.h>

...

> +       ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
> +                                   &msg, sizeof(msg));
> +       if (ret)
> +               return ret;

> +       else if (msg.ret)

Redundant 'else'

> +               return -EIO;

...

> +       ret = rpi_firmware_property(firmware, RPI_FIRMWARE_GET_POE_HAT_VAL,
> +                                   &msg, sizeof(msg));
> +       if (ret)
> +               return ret;

> +       else if (msg.ret)

Ditto.

> +               return -EIO;

...

> +       firmware_node = of_get_parent(dev->of_node);
> +       if (!firmware_node) {
> +               dev_err(dev, "Missing firmware node\n");
> +               return -ENOENT;
> +       }
> +
> +       firmware = rpi_firmware_get(firmware_node);
> +       of_node_put(firmware_node);
> +       if (!firmware)
> +               return -EPROBE_DEFER;

Looks like a hack.

...

> +       ret = pwmchip_remove(&rpipwm->chip);
> +       if (!ret)
> +               rpi_firmware_put(rpipwm->firmware);
> +
> +       return ret;

Can't you use the usual pattern?

  ret = ...
  if (ret)
    return ret;
  ...
  return 0;
Nicolas Saenz Julienne Oct. 26, 2020, 2:02 p.m. UTC | #2
Hi Andy, thanks for the review!

On Thu, 2020-10-22 at 21:53 +0300, Andy Shevchenko wrote:
> On Thu, Oct 22, 2020 at 9:05 PM Nicolas Saenz Julienne
> <nsaenzjulienne@suse.de> 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.
> >  drivers/pwm/pwm-raspberrypi.c | 221 ++++++++++++++++++++++++++++++++++
> 
> Name is completely confusing.
> Please, make it unique enough to understand that this is exactly the
> device it serves for.
> 
> For example, pwm-rpi-poe is better.

Sounds reasonable, I'll change that.

> 
> ...
> 
> > + *  - Only normal polarity
> 
> Can't it be emulated? Isn't it 100% - duty cycle % ?

I guess it can, OTOH given the rather specific use case, I doubt it'll be
worth the effort.

> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/pwm.h>
> 
> ...
> 
> > +       ret = rpi_firmware_property(firmware, RPI_FIRMWARE_SET_POE_HAT_VAL,
> > +                                   &msg, sizeof(msg));
> > +       if (ret)
> > +               return ret;
> > +       else if (msg.ret)
> 
> Redundant 'else'

Noted.

> > +       firmware_node = of_get_parent(dev->of_node);
> > +       if (!firmware_node) {
> > +               dev_err(dev, "Missing firmware node\n");
> > +               return -ENOENT;
> > +       }
> > +
> > +       firmware = rpi_firmware_get(firmware_node);
> > +       of_node_put(firmware_node);
> > +       if (!firmware)
> > +               return -EPROBE_DEFER;
> 
> Looks like a hack.

This is the pattern we've been using on all firmware dependent devices so far.
Feel free to suggest a better way, I'll be happy to look into it.

> 
> ...
> 
> > +       ret = pwmchip_remove(&rpipwm->chip);
> > +       if (!ret)
> > +               rpi_firmware_put(rpipwm->firmware);
> > +
> > +       return ret;
> 
> Can't you use the usual pattern?

Yes of course. Don't know why I went this way.

Regards,
Nicolas
diff mbox series

Patch

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 63be5362fd3a..b0ffb1e690c0 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -379,6 +379,15 @@  config PWM_PXA
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-pxa.
 
+config PWM_RASPBERRYPI
+	tristate "Raspberry Pi Firwmware 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 cbdcd55d69ee..b557b549d9f3 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -35,6 +35,7 @@  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-$(CONFIG_PWM_RASPBERRYPI)	+= pwm-raspberrypi.o
 obj-$(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.c b/drivers/pwm/pwm-raspberrypi.c
new file mode 100644
index 000000000000..72dc0fc5a206
--- /dev/null
+++ b/drivers/pwm/pwm-raspberrypi.c
@@ -0,0 +1,221 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2020 Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
+ * 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-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 *to_raspberrypi_pwm(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;
+	else 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;
+	else 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 = to_raspberrypi_pwm(chip);
+
+	state->period = RPI_PWM_PERIOD_NS;
+	state->duty_cycle = DIV_ROUND_CLOSEST(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 = to_raspberrypi_pwm(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_CLOSEST_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: %d\n", 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: %d\n", 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 = rpi_firmware_get(firmware_node);
+	of_node_put(firmware_node);
+	if (!firmware)
+		return -EPROBE_DEFER;
+
+	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: %d\n", 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);
+	int ret;
+
+	ret = pwmchip_remove(&rpipwm->chip);
+	if (!ret)
+		rpi_firmware_put(rpipwm->firmware);
+
+	return ret;
+}
+
+static const struct of_device_id raspberrypi_pwm_of_match[] = {
+	{ .compatible = "raspberrypi,firmware-pwm", },
+	{ }
+};
+MODULE_DEVICE_TABLE(of, raspberrypi_pwm_of_match);
+
+static struct platform_driver raspberrypi_pwm_driver = {
+	.driver = {
+		.name = "raspberrypi-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@suse.de>");
+MODULE_DESCRIPTION("Raspberry Pi Firwmare Based PWM Bus Driver");
+MODULE_LICENSE("GPL v2");