Re: [PATCH v4 2/2] leds: add LED driver for EL15203000 board

[Jacek Anaszewski <jacek.anaszewski@gmail.com>]

Hi Oleh,

Please find my review remarks below.

On 8/8/19 10:32 PM, Oleh Kravchenko wrote:
> This patch adds a LED class driver for the RGB LEDs found on
> the Crane Merchandising System EL15203000 LEDs board
> (aka RED LEDs board).
> 
> Signed-off-by: Oleh Kravchenko <oleg@kaa.org.ua>
> ---
>  .../testing/sysfs-class-led-driver-el15203000 |  22 +
>  drivers/leds/Kconfig                          |  13 +
>  drivers/leds/Makefile                         |   1 +
>  drivers/leds/leds-el15203000.c                | 478 ++++++++++++++++++
>  4 files changed, 514 insertions(+)
>  create mode 100644 Documentation/ABI/testing/sysfs-class-led-driver-el15203000
>  create mode 100644 drivers/leds/leds-el15203000.c
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-led-driver-el15203000 b/Documentation/ABI/testing/sysfs-class-led-driver-el15203000
> new file mode 100644
> index 000000000000..91a483e493d9
> --- /dev/null
> +++ b/Documentation/ABI/testing/sysfs-class-led-driver-el15203000
> @@ -0,0 +1,22 @@
> +What:		/sys/class/leds/<led>/hw_pattern
> +Date:		August 2019
> +KernelVersion:	5.3
> +Description:
> +		Specify a hardware pattern for the EL15203000 LED.
> +		The LEDs board supports only predefined patterns by firmware
> +		for specific LEDs.
> +
> +		Breathing mode for Screen frame light tube:
> +		"0 4000 1 4000"
> +
> +		Cascade mode for Pipe LED:
> +		"1 800 2 800 4 800 8 800 16 800 1 800 2 800 4 800 8 800 16 800"

There's no point in repeating same sequence. Just require to provide it
once:

"1 800 2 800 4 800 8 800 16 800"

> +
> +		Inverted cascade mode for Pipe LED:
> +		"30 800 29 800 27 800 23 800 15 800 30 800 29 800 27 800 23 800 15 800"

The same story:

"30 800 29 800 27 800 23 800 15 800"

> +
> +		Bounce mode for Pipe LED:
> +		"1 800 2 800 4 800 8 800 16 800 16 800 8 800 4 800 2 800 1 800"
> +
> +		Inverted bounce mode for Pipe LED:
> +		"30 800 29 800 27 800 23 800 15 800 15 800 23 800 27 800 29 800 30 800"

These can be left as they are now.

> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 760f73a49c9f..0cbdb9ba5213 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -129,6 +129,19 @@ config LEDS_CR0014114
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called leds-cr0014114.
>  
> +config LEDS_EL15203000
> +	tristate "LED Support for Crane EL15203000"
> +	depends on LEDS_CLASS
> +	depends on SPI
> +	depends on OF
> +	help
> +	  This option enables support for EL15203000 LED Board
> +	  (aka RED LED board) which is widely used in coffee vending
> +	  machines produced by Crane Merchandising Systems.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called leds-el15203000.
> +
>  config LEDS_LM3530
>  	tristate "LCD Backlight driver for LM3530"
>  	depends on LEDS_CLASS
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index 1e9702ebffee..1f193ffc2feb 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -85,6 +85,7 @@ obj-$(CONFIG_LEDS_LM3601X)		+= leds-lm3601x.o
>  # LED SPI Drivers
>  obj-$(CONFIG_LEDS_CR0014114)		+= leds-cr0014114.o
>  obj-$(CONFIG_LEDS_DAC124S085)		+= leds-dac124s085.o
> +obj-$(CONFIG_LEDS_EL15203000)		+= leds-el15203000.o
>  
>  # LED Userspace Drivers
>  obj-$(CONFIG_LEDS_USER)			+= uleds.o
> diff --git a/drivers/leds/leds-el15203000.c b/drivers/leds/leds-el15203000.c
> new file mode 100644
> index 000000000000..c62da5ec6630
> --- /dev/null
> +++ b/drivers/leds/leds-el15203000.c
> @@ -0,0 +1,478 @@
> +// SPDX-License-Identifier: GPL-2.0
> +// Copyright (c) 2019 Crane Merchandising Systems. All rights reserved.
> +// Copyright (C) 2019 Oleh Kravchenko <oleg@kaa.org.ua>
> +
> +#include <linux/delay.h>
> +#include <linux/leds.h>
> +#include <linux/limits.h>
> +#include <linux/module.h>
> +#include <linux/of_device.h>
> +#include <linux/spi/spi.h>
> +#include <uapi/linux/uleds.h>
> +
> +/*
> + * EL15203000 SPI protocol description:
> + * +-----+------------+
> + * | LED | BRIGHTNESS |
> + * +-----+------------+
> + * |  1  |      1     |
> + * +-----+------------+
> + * (*) LEDs MCU board expects 20 msec delay per byte.
> + *
> + * LEDs:
> + * +----------+--------------+-------------------------------------------+
> + * |    ID    |     NAME     |         DESCRIPTION                       |
> + * +----------+--------------+-------------------------------------------+
> + * | 'P' 0x50 |     Pipe     | Consists from 5 LEDs, controlled by board |
> + * +----------+--------------+-------------------------------------------+
> + * | 'S' 0x53 | Screen frame | Light tube around the screen              |
> + * +----------+--------------+-------------------------------------------+
> + * | 'V' 0x56 | Vending area | Highlights a cup of coffee                |
> + * +----------+--------------+-------------------------------------------+
> + *
> + * BRIGHTNESS:
> + * +----------+-----------------+--------------+--------------+
> + * |  VALUES  |       PIPE      | SCREEN FRAME | VENDING AREA |
> + * +----------+-----------------+--------------+--------------+
> + * | '0' 0x30 |                      Off                      |
> + * +----------+-----------------------------------------------+
> + * | '1' 0x31 |                      On                       |
> + * +----------+-----------------+--------------+--------------+
> + * | '2' 0x32 |     Cascade     |   Breathing  |
> + * +----------+-----------------+--------------+
> + * | '3' 0x33 | Inverse cascade |
> + * +----------+-----------------+
> + * | '4' 0x34 |     Bounce      |
> + * +----------+-----------------+
> + * | '5' 0x35 | Inverse bounce  |
> + * +----------+-----------------+
> + */
> +
> +/* EL15203000 default settings */
> +#define EL_FW_DELAY_USEC	20000
> +
> +enum el15203000_brightness {

Please change 'brightness' to 'command' or so. Brightness is misleading
since this device supports in fact only one level of brightness for
non-pattern use case.

> +	/* for all LEDs */
> +	EL_OFF			= '0',
> +	EL_ON			= '1',
> +
> +	/* for Screen LED */
> +	EL_SCREEN_BREATHING	= '2',
> +
> +	/* for Pipe LED */
> +	EL_PIPE_CASCADE		= '2',
> +	EL_PIPE_INV_CASCADE	= '3',
> +	EL_PIPE_BOUNCE		= '4',
> +	EL_PIPE_INV_BOUNCE	= '5',
> +};
> +
> +struct el15203000_led {
> +	struct el15203000	*priv;
> +	struct led_classdev	ldev;
> +	char			name[LED_MAX_NAME_SIZE];

This field will not be needed if we switch to
devm_led_classdev_register_ext().

> +	u8			reg;
> +};
> +
> +struct el15203000 {
> +	struct device		*dev;
> +	struct mutex		lock;
> +	struct spi_device	*spi;
> +	unsigned long		delay;
> +	size_t			count;
> +	struct el15203000_led	leds[];
> +};
> +
> +static int el15203000_cmd(struct el15203000_led *led, u8 brightness)
> +{
> +	int		ret;
> +	u8		cmd[2];
> +	size_t		i;
> +	unsigned long	jdelay, udelay, now;
> +
> +	mutex_lock(&led->priv->lock);
> +
> +	dev_dbg(led->priv->dev, "Set brightness of %s to %d",
> +		led->name, brightness);
> +
> +	/* to avoid SPI mistiming with firmware we should wait some time */
> +	now = jiffies;
> +	if (time_after(led->priv->delay, now)) {
> +		jdelay = led->priv->delay - now;
> +		udelay = jiffies_to_usecs(jdelay);
> +
> +		dev_dbg(led->priv->dev, "Wait %luus (%lu jiffies) to sync",
> +			udelay, jdelay);
> +
> +		usleep_range(udelay, udelay + 1);
> +	}
> +
> +	cmd[0] = led->reg;
> +	cmd[1] = brightness;
> +
> +	for (i = 0; i < ARRAY_SIZE(cmd); i++) {
> +		if (i)
> +			usleep_range(EL_FW_DELAY_USEC,
> +				     EL_FW_DELAY_USEC + 1);
> +
> +		ret = spi_write(led->priv->spi, &cmd[i], sizeof(cmd[i]));
> +		if (ret) {
> +			dev_err(led->priv->dev,
> +				"spi_write() error %d", ret);
> +			break;
> +		}
> +	}
> +
> +	led->priv->delay = jiffies + usecs_to_jiffies(EL_FW_DELAY_USEC);
> +
> +	mutex_unlock(&led->priv->lock);
> +
> +	return ret;
> +}
> +
> +static int el15203000_set_blocking(struct led_classdev *ldev,
> +				   enum led_brightness brightness)
> +{
> +	struct el15203000_led	*led = container_of(ldev,
> +						    struct el15203000_led,
> +						    ldev);
> +
> +	return el15203000_cmd(led, brightness == LED_OFF ? EL_OFF : EL_ON);
> +}
> +
> +static int led_pattern_cmp(const struct led_pattern *p1, u32 p1_len,
> +			   const struct led_pattern *p2, u32 p2_len)
> +{
> +	u32 i;
> +
> +	if (p1_len != p2_len)
> +		return -1;
> +
> +	for (i = 0; i < p1_len; i ++)
> +		if (p1[i].delta_t != p2[i].delta_t ||
> +		    p1[i].brightness != p2[i].brightness)
> +			return -1;
> +
> +	return 0;
> +}
> +
> +int el15203000_pattern_set_S(struct led_classdev *ldev,
> +			     struct led_pattern *pattern,
> +			     u32 len, int repeat)
> +{
> +	struct el15203000_led	*led = container_of(ldev,
> +						    struct el15203000_led,
> +						    ldev);
> +	struct led_pattern	scr_pattern[] = {{
> +		.delta_t	= 4000,
> +		.brightness	= 0,
> +	}, {
> +		.delta_t	= 4000,
> +		.brightness	= 1,
> +	}};
> +
> +	if (repeat > 0)
> +		return -EINVAL;
> +
> +	if (led_pattern_cmp(scr_pattern, ARRAY_SIZE(scr_pattern), pattern, len))
> +		return -EINVAL;
> +
> +	dev_dbg(led->priv->dev, "Breathing mode for '%s'", led->name);
> +
> +	return el15203000_cmd(led, EL_SCREEN_BREATHING);
> +}
> +
> +int el15203000_pattern_set_P(struct led_classdev *ldev,
> +			   struct led_pattern *pattern,
> +			   u32 len, int repeat)
> +{
> +	struct el15203000_led	*led = container_of(ldev,
> +						    struct el15203000_led,
> +						    ldev);
> +
> +	struct led_pattern cascade[] = {{
> +		.delta_t	= 800,
> +		.brightness	= 1,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 2,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 4,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 8,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 16,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 1,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 2,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 4,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 8,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 16,
> +	}};
> +
> +	struct led_pattern inv_cascade[] = {{
> +		.delta_t	= 800,
> +		.brightness	= 30,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 29,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 27,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 23,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 15,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 30,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 29,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 27,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 23,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 15,
> +	}};
> +
> +	struct led_pattern	bounce[] = {{
> +		.delta_t	= 800,
> +		.brightness	= 1,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 2,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 4,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 8,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 16,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 16,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 8,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 4,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 2,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 1,
> +	}};
> +
> +	struct led_pattern	inv_bounce[] = {{
> +		.delta_t	= 800,
> +		.brightness	= 30,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 29,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 27,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 23,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 15,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 15,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 23,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 27,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 29,
> +	}, {
> +		.delta_t	= 800,
> +		.brightness	= 30,
> +	}};

There is no need for these arrays. We can come up with formulas for
validating the pattern tuples. Basically all of them involve differences
in brightness being powers of two:

"1 800 2 800 4 800 8 800 16 800"

Here each next step should be equal to (1 << i) staring from i = 0.

"30 800 29 800 27 800 23 800 15 800"

brightness = 30;
for (i = 0; i < pattern_len; i++) {
	br_diff = (i > 0) ? (1 << (i - 1)) : 0;
	brightness -= br_diff;
}

"1 800 2 800 4 800 8 800 16 800 16 800 8 800 4 800 2 800 1 800"

"30 800 29 800 27 800 23 800 15 800 15 800 23 800 27 800 29 800 30 800"

Above two can be handled by slightly modifying what I proposed above.

And for delta_t just require by default always 800.

> +	if (repeat > 0)
> +		return -EINVAL;
> +
> +	if (!led_pattern_cmp(cascade, ARRAY_SIZE(cascade), pattern, len)) {
> +		dev_dbg(led->priv->dev, "Cascade mode for '%s'", led->name);
> +		return el15203000_cmd(led, EL_PIPE_CASCADE);
> +	} else if (!led_pattern_cmp(inv_cascade, ARRAY_SIZE(inv_cascade), pattern, len)) {
> +		dev_dbg(led->priv->dev, "Inverse cascade mode for '%s'", led->name);
> +		return el15203000_cmd(led, EL_PIPE_INV_CASCADE);
> +	} else if (!led_pattern_cmp(bounce, ARRAY_SIZE(bounce), pattern, len)) {
> +		dev_dbg(led->priv->dev, "Bounce mode for '%s'", led->name);
> +		return el15203000_cmd(led, EL_PIPE_BOUNCE);
> +	} else if (!led_pattern_cmp(inv_bounce, ARRAY_SIZE(inv_bounce), pattern, len)) {
> +		dev_dbg(led->priv->dev, "Inverse bounce mode for '%s'", led->name);
> +		return el15203000_cmd(led, EL_PIPE_INV_BOUNCE);
> +	}
> +
> +	return -EINVAL;
> +}
> +
> +int el15203000_pattern_clear(struct led_classdev *ldev)
> +{
> +	struct el15203000_led	*led = container_of(ldev,
> +						    struct el15203000_led,
> +						    ldev);
> +
> +	return el15203000_cmd(led, EL_OFF);
> +}
> +
> +static int el15203000_probe_dt(struct el15203000 *priv)
> +{
> +	size_t			i = 0;
> +	struct el15203000_led	*led;
> +	struct fwnode_handle	*child;
> +	int			ret;
> +	const char		*str;
> +	u32			reg;
> +
> +	device_for_each_child_node(priv->dev, child) {
		struct led_init_data init_data = {};

Please add above declaration here.

> +		led = &priv->leds[i];
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret) {
> +			dev_err(priv->dev, "LED without ID number");
> +			fwnode_handle_put(child);
> +
> +			return ret;
> +		}
> +
> +		if (reg > U8_MAX) {
> +			dev_err(priv->dev, "LED value %d is invalid", reg);
> +			fwnode_handle_put(child);
> +
> +			return -EINVAL;
> +		}
> +
> +		led->reg = reg;
> +
> +		ret = fwnode_property_read_string(child, "label", &str);
> +		if (ret)
> +			str = ":";
> +		snprintf(led->name, sizeof(led->name), "el15203000:%s", str);

And instead of the four above lines please just do the below assignment:

		init_data.fwnode = child;

but let's do it right before calling devm_led_classdev_register_ext().

> +
> +		fwnode_property_read_string(child, "linux,default-trigger",
> +					    &led->ldev.default_trigger);
> +
> +		led->ldev.max_brightness	  = LED_ON;
> +		led->priv			  = priv;
> +		led->ldev.name			  = led->name;

Please also remove the above line.

> +		led->ldev.brightness_set_blocking = el15203000_set_blocking;
> +
> +		if (reg == 'S') {
> +			led->ldev.pattern_set	= el15203000_pattern_set_S;
> +			led->ldev.pattern_clear	= el15203000_pattern_clear;
> +		} else if (reg == 'P') {
> +			led->ldev.pattern_set	= el15203000_pattern_set_P;
> +			led->ldev.pattern_clear	= el15203000_pattern_clear;
> +		}
> +
> +		ret = devm_led_classdev_register(priv->dev, &led->ldev);

And here let's switch to the new LED registration API:

		ret = devm_led_classdev_register_ext(priv->dev, &led->ldev, &init_data);


> +		if (ret) {
> +			dev_err(priv->dev,
> +				"failed to register LED device %s, err %d",
> +				led->name, ret);
> +			fwnode_handle_put(child);
> +			return ret;
> +		}
> +
> +		i++;
> +	}
> +
> +	return ret;
> +}
> +
> +static int el15203000_probe(struct spi_device *spi)
> +{
> +	struct el15203000	*priv;
> +	size_t			count;
> +	int			ret;
> +
> +	count = device_get_child_node_count(&spi->dev);
> +	if (!count) {
> +		dev_err(&spi->dev, "LEDs are not defined in device tree!");
> +		return -ENODEV;
> +	}
> +
> +	priv = devm_kzalloc(&spi->dev, struct_size(priv, leds, count),
> +			    GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	mutex_init(&priv->lock);
> +	priv->count	= count;
> +	priv->dev	= &spi->dev;
> +	priv->spi	= spi;
> +	priv->delay	= jiffies -
> +			  usecs_to_jiffies(EL_FW_DELAY_USEC);
> +
> +	ret = el15203000_probe_dt(priv);
> +	if (ret)
> +		return ret;
> +
> +	spi_set_drvdata(spi, priv);
> +	dev_dbg(priv->dev, "%zd LEDs registered", priv->count);

Please remove this debug log.

> +
> +	return 0;
> +}
> +
> +static int el15203000_remove(struct spi_device *spi)
> +{
> +	struct el15203000 *priv = spi_get_drvdata(spi);
> +
> +	mutex_destroy(&priv->lock);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id el15203000_dt_ids[] = {
> +	{ .compatible = "crane,el15203000", },
> +	{},
> +};
> +
> +MODULE_DEVICE_TABLE(of, el15203000_dt_ids);
> +
> +static struct spi_driver el15203000_driver = {
> +	.probe		= el15203000_probe,
> +	.remove		= el15203000_remove,
> +	.driver = {
> +		.name		= KBUILD_MODNAME,
> +		.of_match_table	= el15203000_dt_ids,
> +	},
> +};
> +
> +module_spi_driver(el15203000_driver);
> +
> +MODULE_AUTHOR("Oleh Kravchenko <oleg@kaa.org.ua>");
> +MODULE_DESCRIPTION("el15203000 LED driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_ALIAS("spi:el15203000");
> 

Please also fix the issues checkpatch.pl complains about.

-- 
Best regards,
Jacek Anaszewski