Date:   Tue, 5 Jul 2022 12:37:05 +0200
From:   Marek Behún <kabel@...nel.org>
To:     Pali Rohár <pali@...nel.org>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] leds: Add support for Turris 1.x LEDs

On Tue,  5 Jul 2022 02:04:48 +0200
Pali Rohár <pali@...nel.org> wrote:

> This adds support for the RGB LEDs found on the front panel of the
> Turris 1.x routers. There are 8 RGB LEDs that are controlled by
> CZ.NIC CPLD firmware running on Lattice FPGA.
> 
> CPLD firmware provides HW triggering mode for all LEDs except WiFi LED
> which is automatically enabled after power on reset. LAN LEDs share HW
> registers for RGB colors settings, so it is not possible to set different
> colors for individual LAN LEDs.
> 
> CZ.NIC CPLD firmware is open source and available at:
> https://gitlab.nic.cz/turris/hw/turris_cpld/-/blob/master/CZ_NIC_Router_CPLD.v
> 
> This driver uses the multicolor LED framework and HW led triggers.
> 
> Signed-off-by: Pali Rohár <pali@...nel.org>
> ---
>  .../testing/sysfs-class-led-driver-turris1x   |  23 +
>  drivers/leds/Kconfig                          |   9 +
>  drivers/leds/Makefile                         |   1 +
>  drivers/leds/leds-turris-1x.c                 | 412 ++++++++++++++++++
>  4 files changed, 445 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-led-driver-turris1x
>  create mode 100644 drivers/leds/leds-turris-1x.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-driver-turris1x b/Documentation/ABI/testing/sysfs-class-led-driver-turris1x
> new file mode 100644
> index 000000000000..02be9197554d
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-led-driver-turris1x
> @@ -0,0 +1,23 @@
> +What:		/sys/class/leds/<led>/device/brightness
> +Date:		July 2022
> +KernelVersion:	5.20
> +Contact:	Pali Rohár <pali@...nel.org>
> +Description:	(RW) On the back size of the Turris 1.x routers there is also
> +		a button which can be used to control the intensity of all the
> +		LEDs at once, so that if they are too bright, user can dim them.
> +
> +		The CPLD firmware cycles between 8 levels of this global
> +		brightness (from 100% to 0%), but this setting can have any
> +		integer value between 0 and 255. It is therefore convenient to be
> +		able to change this setting from software.
> +
> +		Format: %u
> +
> +What:		/sys/class/leds/<led>/device/brightness_values
> +Date:		July 2022
> +KernelVersion:	5.20
> +Contact:	Pali Rohár <pali@...nel.org>
> +Description:	(RW) Values of all 8 levels between which CPLD firmware cycles
> +		when brightness buffer is pressed.

*button

> +		Format: %u %u %u %u %u %u %u %u
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index a49979f41eee..71caf45c8ac3 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -157,6 +157,15 @@ config LEDS_EL15203000
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called leds-el15203000.
>  
> +config LEDS_TURRIS_1X
> +	tristate "LED support for CZ.NIC's Turris 1.x"
> +	depends on LEDS_CLASS_MULTICOLOR
> +	depends on OF
> +	select LEDS_TRIGGERS
> +	help
> +	  This option enables support for LEDs found on the front side of
> +	  CZ.NIC's Turris 1.x routers.
> +
>  config LEDS_TURRIS_OMNIA
>  	tristate "LED support for CZ.NIC's Turris Omnia"
>  	depends on LEDS_CLASS_MULTICOLOR
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 4fd2f92cd198..de08083dbbca 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -82,6 +82,7 @@ obj-$(CONFIG_LEDS_TCA6507)		+= leds-tca6507.o
>  obj-$(CONFIG_LEDS_TI_LMU_COMMON)	+= leds-ti-lmu-common.o
>  obj-$(CONFIG_LEDS_TLC591XX)		+= leds-tlc591xx.o
>  obj-$(CONFIG_LEDS_TPS6105X)		+= leds-tps6105x.o
> +obj-$(CONFIG_LEDS_TURRIS_1X)		+= leds-turris-1x.o
>  obj-$(CONFIG_LEDS_TURRIS_OMNIA)		+= leds-turris-omnia.o
>  obj-$(CONFIG_LEDS_WM831X_STATUS)	+= leds-wm831x-status.o
>  obj-$(CONFIG_LEDS_WM8350)		+= leds-wm8350.o
> diff --git a/drivers/leds/leds-turris-1x.c b/drivers/leds/leds-turris-1x.c
> new file mode 100644
> index 000000000000..bd566f5210c7
> --- /dev/null
> +++ b/drivers/leds/leds-turris-1x.c
> @@ -0,0 +1,412 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// (C) 2022 Pali Rohár <pali@...nel.org>
> +//
> +// CZ.NIC's Turris 1.x LEDs driver, controlled by CPLD firmware:
> +// https://gitlab.nic.cz/turris/hw/turris_cpld/-/blob/master/CZ_NIC_Router_CPLD.v
> +
> +#include <linux/i2c.h>
> +#include <linux/led-class-multicolor.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include "leds.h"
> +
> +/* LED registers starts at byte 0x13 in CPLD memory map */
> +#define TURRIS1X_LED_REG_OFF(reg) ((reg)-0x13)
> +
> +/* LEDs 1-5 share common register for setting brightness */
> +#define TURRIS1X_LED_BRIGHTNESS_OFF(idx)	({ const u8 _idx = (idx) & 7; \
> +						   (_idx == 0) ? 0 : \
> +						   (_idx <= 5) ? 1 : \
> +						   (_idx - 4); })
> +
> +#define TURRIS1X_LED_BRIGHTNESS_REG(idx, color)	TURRIS1X_LED_REG_OFF(0x13 + \
> +						  3 * TURRIS1X_LED_BRIGHTNESS_OFF(idx) + \
> +						  ((color) & 3))
> +#define TURRIS1X_LED_GLOBAL_LEVEL_REG		TURRIS1X_LED_REG_OFF(0x20)
> +#define TURRIS1X_LED_GET_GLOBAL_BRIGHTNESS_REG	TURRIS1X_LED_REG_OFF(0x21)
> +#define TURRIS1X_LED_SW_OVERRIDE_REG		TURRIS1X_LED_REG_OFF(0x22)
> +#define TURRIS1X_LED_SW_DISABLE_REG		TURRIS1X_LED_REG_OFF(0x23)
> +#define TURRIS1X_LED_GLOBAL_BRIGHTNESS_REG(lvl)	TURRIS1X_LED_REG_OFF(0x28 + ((lvl) & 7))
> +
> +struct turris1x_led {
> +	struct led_classdev_mc mc_cdev;
> +	struct mc_subled subled_info[3];
> +	u32 reg;
> +	bool registered;
> +};
> +
> +#define to_turris1x_led(l)	container_of(l, struct turris1x_led, mc_cdev)
> +
> +struct turris1x_leds {
> +	void __iomem *regs;
> +	struct mutex lock;
> +	struct turris1x_led leds[8];
> +};
> +
> +static struct led_hw_trigger_type turris1x_hw_trigger_type;
> +
> +static int turris1x_hwtrig_activate(struct led_classdev *cdev)
> +{
> +	struct turris1x_leds *leds = dev_get_drvdata(cdev->dev->parent);
> +	struct turris1x_led *led = to_turris1x_led(lcdev_to_mccdev(cdev));
> +	u8 val;
> +
> +	/* Disable software control of LED */
> +	mutex_lock(&leds->lock);
> +	val = readb(leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG);
> +	val &= ~BIT(led->reg);
> +	writeb(val, leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG);
> +	mutex_unlock(&leds->lock);
> +
> +	return 0;
> +}
> +
> +static void turris1x_hwtrig_deactivate(struct led_classdev *cdev)
> +{
> +	struct turris1x_leds *leds = dev_get_drvdata(cdev->dev->parent);
> +	struct turris1x_led *led = to_turris1x_led(lcdev_to_mccdev(cdev));
> +	u8 val;
> +
> +	/* Enable software control of LED */
> +	mutex_lock(&leds->lock);
> +	val = readb(leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG);
> +	val |= BIT(led->reg);
> +	writeb(val, leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG);
> +	mutex_unlock(&leds->lock);
> +}
> +
> +static struct led_trigger turris1x_hw_trigger = {
> +	.name		= "turris1x-cpld",
> +	.activate	= turris1x_hwtrig_activate,
> +	.deactivate	= turris1x_hwtrig_deactivate,
> +	.trigger_type	= &turris1x_hw_trigger_type,
> +};
> +
> +static enum led_brightness turris1x_led_brightness_get(struct led_classdev *cdev)
> +{
> +	struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
> +	struct turris1x_leds *leds = dev_get_drvdata(cdev->dev->parent);
> +	struct turris1x_led *led = to_turris1x_led(mc_cdev);
> +
> +	if (!(readb(leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG) & BIT(led->reg)))
> +		return LED_ON;
> +	else if (!(readb(leds->regs + TURRIS1X_LED_SW_DISABLE_REG) & BIT(led->reg)))
> +		return LED_ON;
> +	else
> +		return LED_OFF;
> +}

LED_ON and LED_OFF are deprecated, as says in include/linux/leds.h.
Just return 0 or 1.

> +
> +static int turris1x_led_brightness_set_blocking(struct led_classdev *cdev,
> +						enum led_brightness brightness)
> +{

The register write should be immediate, we don't need to use the
_blocking variant here. On Omnia we need to, cause I2C is slow.

> +	struct led_classdev_mc *mc_cdev = lcdev_to_mccdev(cdev);
> +	struct turris1x_leds *leds = dev_get_drvdata(cdev->dev->parent);
> +	struct turris1x_led *led = to_turris1x_led(mc_cdev);
> +	int i, j;
> +	u8 val;
> +
> +	mutex_lock(&leds->lock);
> +
> +	/* Set new brightness value for each color when LED is enabled */
> +	if (brightness == LED_ON) {

	if (brightness)

So this will also make sure that I can change LED color by writing
new color to multi_intensity and 1 to brightness, even if the LED is in
HW control mode, am I correct?

> +		led_mc_calc_color_components(mc_cdev, brightness);
> +		for (i = 0; i < ARRAY_SIZE(led->subled_info); i++)
> +			writeb(mc_cdev->subled_info[i].brightness,
> +			       leds->regs + TURRIS1X_LED_BRIGHTNESS_REG(led->reg, i));
> +
> +		/*
> +		 * LEDs 1-5 (LAN) share common color settings in same sets
> +		 * of HW registers and therefore it is not possible to set
> +		 * different colors. So when chaning color of one LED then
> +		 * reflect color change for all of them.
> +		 */
> +		if (led->reg >= 1 && led->reg <= 5) {
> +			for (j = 0; j < ARRAY_SIZE(leds->leds); j++) {
> +				if (leds->leds[j].reg < 1 ||
> +				    leds->leds[j].reg > 5 ||
> +				    leds->leds[j].reg == led->reg)
> +					continue;
> +				for (i = 0; i < ARRAY_SIZE(led->subled_info); i++)
> +					leds->leds[j].mc_cdev.subled_info[i].intensity =
> +						mc_cdev->subled_info[i].intensity;
> +			}

I don't consider this a problem, but suppose that we are rewriting the
other LEDs colors, and at the same time someone is reading from sysfs
the multi_intensity file of a LED that is being rewritten. This can
result in wrong value being read, right? But probably only on multi-core
systems...

> +		}
> +	}
> +
> +	/* Enable / disable LED for software control */
> +	val = readb(leds->regs + TURRIS1X_LED_SW_DISABLE_REG);
> +	if (brightness == LED_ON && (val & BIT(led->reg)))
> +		writeb(val & ~BIT(led->reg),
> +		       leds->regs + TURRIS1X_LED_SW_DISABLE_REG);
> +	else if (brightness == LED_OFF && !(val & BIT(led->reg)))
> +		writeb(val | BIT(led->reg),
> +		       leds->regs + TURRIS1X_LED_SW_DISABLE_REG);

Pls just use brightness or !brightness. Or maybe just write the value?
Is the register write expensive on the CPLD or why are you trying to
avoid it if unnecessary?

> +	mutex_unlock(&leds->lock);
> +
> +	return 0;
> +}
> +
> +static int turris1x_led_register(struct device *dev, struct turris1x_leds *leds,
> +				 struct device_node *np, u8 val_sw_override,
> +				 u8 val_sw_disable)
> +{
> +	struct led_init_data init_data = {};
> +	struct led_classdev *cdev;
> +	struct turris1x_led *led;
> +	int ret, color;
> +	u32 reg;
> +
> +	ret = of_property_read_u32(np, "reg", &reg);
> +	if (ret || reg >= ARRAY_SIZE(leds->leds)) {
> +		dev_err(dev,
> +			"Node %pOF: must contain 'reg' property with values between 0 and %u\n",
> +			np, (unsigned int)ARRAY_SIZE(leds->leds)-1);

Weird that checkpatch doesn't warn about spaces around the minus
operator in ARRAY_SIZE()-1.


> +		return -EINVAL;
> +	}
> +
> +	ret = of_property_read_u32(np, "color", &color);
> +	if (ret || color != LED_COLOR_ID_RGB) {
> +		dev_err(dev,
> +			"Node %pOF: must contain 'color' property with value LED_COLOR_ID_RGB\n",
> +			np);
> +		return -EINVAL;
> +	}
> +
> +	led = &leds->leds[reg];
> +
> +	if (led->registered) {
> +		dev_err(dev, "Node %pOF: duplicate 'reg' property %u\n",
> +			     np, reg);
> +		return -EINVAL;
> +	}
> +
> +	led->registered = true;
> +	led->reg = reg;
> +
> +	led->subled_info[0].color_index = LED_COLOR_ID_RED;
> +	led->subled_info[0].intensity = 255;
> +	led->subled_info[0].channel = 0;
> +	led->subled_info[1].color_index = LED_COLOR_ID_GREEN;
> +	led->subled_info[1].intensity = 255;
> +	led->subled_info[1].channel = 1;
> +	led->subled_info[2].color_index = LED_COLOR_ID_BLUE;
> +	led->subled_info[2].intensity = 255;
> +	led->subled_info[2].channel = 2;
> +
> +	led->mc_cdev.subled_info = led->subled_info;
> +	led->mc_cdev.num_colors = ARRAY_SIZE(led->subled_info);
> +
> +	init_data.fwnode = &np->fwnode;
> +
> +	cdev = &led->mc_cdev.led_cdev;
> +	cdev->max_brightness = LED_ON;

s/LED_ON/1/

> +	cdev->brightness_get = turris1x_led_brightness_get;
> +	cdev->brightness_set_blocking = turris1x_led_brightness_set_blocking;

See above about _blocking.

> +
> +	/* All LEDs except LED 6 (WiFi) can be controller by hardware trigger */
> +	if (reg != 6)
> +		cdev->trigger_type = &turris1x_hw_trigger_type;
> +
> +	/* Disable hardware trigger for LED 6 (WiFi) - allow software control */
> +	if (reg == 6 && !(val_sw_override & BIT(6))) {
> +		if (!(val_sw_disable & BIT(6))) {
> +			val_sw_disable |= BIT(6);
> +			writeb(val_sw_disable,
> +			       leds->regs + TURRIS1X_LED_SW_DISABLE_REG);
> +		}
> +		val_sw_override |= BIT(6);
> +		writeb(val_sw_override,
> +		       leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG);

Again, is the register write that expensive that you try to avoid it if
the corresponding bit has the value you want?

> +	}
> +
> +	if (!(val_sw_override & BIT(reg)))
> +		cdev->default_trigger = turris1x_hw_trigger.name;
> +
> +	if (!(val_sw_override & BIT(reg)) || !(val_sw_disable & BIT(reg)))
> +		cdev->brightness = LED_ON;

s/LED_ON/1/

> +	ret = devm_led_classdev_multicolor_register_ext(dev, &led->mc_cdev,
> +							&init_data);
> +	if (ret) {
> +		dev_err(dev, "Cannot register LED %pOF: %i\n", np, ret);
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static ssize_t brightness_show(struct device *dev, struct device_attribute *a,
> +			       char *buf)
> +{
> +	struct turris1x_leds *leds = dev_get_drvdata(dev);
> +	unsigned int brightness;
> +
> +	/*
> +	 * Current brightness value is available in read-only register
> +	 * TURRIS1X_LED_GET_GLOBAL_BRIGHTNESS_REG. Equivalent code is:
> +	 * level = readb(leds->regs + TURRIS1X_LED_GLOBAL_LEVEL_REG) & 7;
> +	 * brightness = readb(leds->regs + TURRIS1X_LED_GLOBAL_BRIGHTNESS_REG(level));
> +	 */
> +	brightness = readb(leds->regs + TURRIS1X_LED_GET_GLOBAL_BRIGHTNESS_REG);
> +
> +	return sprintf(buf, "%u\n", brightness);
> +}
> +
> +static ssize_t brightness_store(struct device *dev, struct device_attribute *a,
> +				const char *buf, size_t count)
> +{
> +	struct turris1x_leds *leds = dev_get_drvdata(dev);
> +	int best_error, error, level, value;
> +	unsigned long brightness;
> +	u8 best_level;
> +
> +	if (kstrtoul(buf, 10, &brightness))
> +		return -EINVAL;
> +
> +	if (brightness > 255)
> +		return -EINVAL;
> +
> +	/*
> +	 * Brightness can be set only to one of 8 predefined value levels
> +	 * available in TURRIS1X_LED_GLOBAL_BRIGHTNESS_REG(level) registers.
> +	 * Choose level which has nearest value to the specified brightness.
> +	 */

Hmm. Wouldn't it make more sense to simply have the global brightness
accept values from 0 to 7, instead of mapping it to 256 values? And
call it something like selected_brightness_index?

> +	best_level = 0;
> +	best_error = INT_MAX;
> +	for (level = 0; level < 8; level++) {
> +		value = readb(leds->regs +
> +			      TURRIS1X_LED_GLOBAL_BRIGHTNESS_REG(level));
> +		error = abs(value - (int)brightness);
> +		if (best_error > error) {
> +			best_error = error;
> +			best_level = level;
> +		}
> +	}
> +
> +	writeb(best_level, leds->regs + TURRIS1X_LED_GLOBAL_LEVEL_REG);
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RW(brightness);
> +
> +static ssize_t brightness_values_show(struct device *dev,
> +				      struct device_attribute *a, char *buf)
> +{
> +	struct turris1x_leds *leds = dev_get_drvdata(dev);
> +	unsigned int vals[8];
> +	int i;
> +
> +	for (i = 0; i < 8; i++)
> +		vals[i] = readb(leds->regs +
> +				TURRIS1X_LED_GLOBAL_BRIGHTNESS_REG(i));
> +
> +	return sprintf(buf, "%u %u %u %u %u %u %u %u\n", vals[0], vals[1],
> +		       vals[2], vals[3], vals[4], vals[5], vals[6], vals[7]);
> +}
> +
> +static ssize_t brightness_values_store(struct device *dev,
> +				       struct device_attribute *a,
> +				       const char *buf, size_t count)
> +{
> +	struct turris1x_leds *leds = dev_get_drvdata(dev);
> +	unsigned int vals[8];
> +	int nchars;
> +	int i;
> +
> +	if (sscanf(buf, "%u %u %u %u %u %u %u %u%n", &vals[0], &vals[1],
> +		   &vals[2], &vals[3], &vals[4], &vals[5], &vals[6], &vals[7],
> +		   &nchars) != 8 || nchars + 1 < count)
> +		return -EINVAL;
> +
> +	for (i = 0; i < 8; i++)
> +		writeb(vals[i],
> +		       leds->regs + TURRIS1X_LED_GLOBAL_BRIGHTNESS_REG(i));
> +
> +	return count;
> +}
> +static DEVICE_ATTR_RW(brightness_values);
> +
> +static struct attribute *turris1x_leds_controller_attrs[] = {
> +	&dev_attr_brightness.attr,
> +	&dev_attr_brightness_values.attr,
> +	NULL,
> +};
> +ATTRIBUTE_GROUPS(turris1x_leds_controller);
> +
> +static int turris1x_leds_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct device_node *np = dev_of_node(dev);
> +	struct device_node *child;
> +	struct turris1x_leds *leds;
> +	struct resource *res;
> +	void __iomem *regs;
> +	u8 val_sw_override;
> +	u8 val_sw_disable;
> +	int ret;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res)
> +		return -ENODEV;
> +
> +	regs = devm_ioremap_resource(dev, res);
> +	if (IS_ERR(regs))
> +		return PTR_ERR(regs);
> +
> +	leds = devm_kzalloc(dev, sizeof(*leds), GFP_KERNEL);
> +	if (!leds)
> +		return -ENOMEM;
> +
> +	platform_set_drvdata(pdev, leds);
> +
> +	leds->regs = regs;
> +	mutex_init(&leds->lock);
> +
> +	ret = devm_led_trigger_register(dev, &turris1x_hw_trigger);
> +	if (ret) {
> +		dev_err(dev, "Cannot register private LED trigger: %d\n", ret);
> +		return ret;
> +	}
> +
> +	val_sw_override = readb(leds->regs + TURRIS1X_LED_SW_OVERRIDE_REG);
> +	val_sw_disable = readb(leds->regs + TURRIS1X_LED_SW_DISABLE_REG);
> +
> +	for_each_available_child_of_node(np, child) {
> +		ret = turris1x_led_register(dev, leds, child,
> +					    val_sw_override, val_sw_disable);
> +		if (ret) {
> +			of_node_put(child);
> +			return ret;
> +		}
> +	}
> +
> +	ret = devm_device_add_groups(dev, turris1x_leds_controller_groups);
> +	if (ret) {
> +		dev_err(dev, "Could not add attribute group!\n");
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id of_turris1x_leds_match[] = {
> +	{ .compatible = "cznic,turris1x-leds" },
> +	{},
> +};
> +
> +static struct platform_driver turris1x_leds_driver = {
> +	.probe = turris1x_leds_probe,
> +	.driver = {
> +		.name = "turris1x_leds",
> +		.of_match_table = of_turris1x_leds_match,
> +	},
> +};
> +module_platform_driver(turris1x_leds_driver);
> +
> +MODULE_AUTHOR("Pali Rohár <pali@...nel.org>");
> +MODULE_DESCRIPTION("CZ.NIC's Turris 1.x LEDs");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("platform:turris1x_leds");

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