Date:	Tue, 21 Jun 2016 17:29:09 +0200
From:	Jacek Anaszewski <j.anaszewski@...sung.com>
To:	Florian Vaussard <florian.vaussard@...il.com>
Cc:	devicetree@...r.kernel.org, Richard Purdie <rpurdie@...ys.net>,
	Rob Herring <robh+dt@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org,
	Florian Vaussard <florian.vaussard@...g-vd.ch>
Subject: Re: [PATCH 2/2] leds: Add driver for NCP5623 3-channel I2C LED driver

Hi Florian,

Thanks for the patch. Please refer to my comments in the code.

On 06/21/2016 09:29 AM, Florian Vaussard wrote:
> The NCP5623 is a 3-channel LED driver from On Semiconductor controlled
> through I2C. The PWM of each channel can be independently set with 32
> distinct levels. In addition, the intensity of the current source can be
> globally set using an external bias resistor fixing the reference
> current (Iref) and a dedicated register (ILED), following the
> relationship:
>
> I = 2400*Iref/(31-ILED)
>
> with Iref = Vref/Rbias, and Vref = 0.6V.
>
> Signed-off-by: Florian Vaussard <florian.vaussard@...g-vd.ch>
> ---
>   drivers/leds/Kconfig        |  11 ++
>   drivers/leds/Makefile       |   1 +
>   drivers/leds/leds-ncp5623.c | 265 ++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 277 insertions(+)
>   create mode 100644 drivers/leds/leds-ncp5623.c
>
> diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
> index 5ae2834..6d3e44d 100644
> --- a/drivers/leds/Kconfig
> +++ b/drivers/leds/Kconfig
> @@ -588,6 +588,17 @@ config LEDS_BLINKM
>   	  This option enables support for the BlinkM RGB LED connected
>   	  through I2C. Say Y to enable support for the BlinkM LED.
>
> +config LEDS_NCP5623
> +	tristate "LED Support for NCP5623 I2C chip"
> +	depends on LEDS_CLASS
> +	depends on I2C
> +	help
> +	  This option enables support for LEDs connected to NCP5623
> +	  LED driver chips accessed via the I2C bus.
> +	  Driver supports brightness control.
> +
> +	  Say Y to enable this driver.
> +
>   config LEDS_POWERNV
>   	tristate "LED support for PowerNV Platform"
>   	depends on LEDS_CLASS
> diff --git a/drivers/leds/Makefile b/drivers/leds/Makefile
> index cb2013d..a2f0e10 100644
> --- a/drivers/leds/Makefile
> +++ b/drivers/leds/Makefile
> @@ -67,6 +67,7 @@ obj-$(CONFIG_LEDS_KTD2692)		+= leds-ktd2692.o
>   obj-$(CONFIG_LEDS_POWERNV)		+= leds-powernv.o
>   obj-$(CONFIG_LEDS_SEAD3)		+= leds-sead3.o
>   obj-$(CONFIG_LEDS_IS31FL32XX)		+= leds-is31fl32xx.o
> +obj-$(CONFIG_LEDS_NCP5623)		+= leds-ncp5623.o
>
>   # LED SPI Drivers
>   obj-$(CONFIG_LEDS_DAC124S085)		+= leds-dac124s085.o
> diff --git a/drivers/leds/leds-ncp5623.c b/drivers/leds/leds-ncp5623.c
> new file mode 100644
> index 0000000..a341e4a
> --- /dev/null
> +++ b/drivers/leds/leds-ncp5623.c
> @@ -0,0 +1,265 @@
> +/*
> + * Copyright 2016 Florian Vaussard <florian.vaussard@...g-vd.ch>
> + *
> + * Based on leds-tlc591xx.c
> + *
> + * 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 of the License.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/i2c.h>
> +#include <linux/kernel.h>
> +#include <linux/leds.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/slab.h>
> +#include <linux/workqueue.h>
> +
> +#define NCP5623_MAX_LEDS	3
> +#define NCP5623_MAX_STEPS	32
> +#define NCP5623_MAX_CURRENT	31
> +#define NCP5623_MAX_CURRENT_UA	30000
> +
> +#define NCP5623_CMD_SHIFT	5
> +#define CMD_SHUTDOWN		(0x00 << NCP5623_CMD_SHIFT)
> +#define CMD_ILED		(0x01 << NCP5623_CMD_SHIFT)
> +#define CMD_PWM1		(0x02 << NCP5623_CMD_SHIFT)
> +#define CMD_PWM2		(0x03 << NCP5623_CMD_SHIFT)
> +#define CMD_PWM3		(0x04 << NCP5623_CMD_SHIFT)
> +#define CMD_UPWARD_DIM		(0x05 << NCP5623_CMD_SHIFT)
> +#define CMD_DOWNWARD_DIM	(0x06 << NCP5623_CMD_SHIFT)
> +#define CMD_DIM_STEP		(0x07 << NCP5623_CMD_SHIFT)
> +
> +#define NCP5623_DATA_MASK	GENMASK(NCP5623_CMD_SHIFT - 1, 0)
> +
> +#define NCP5623_CMD(cmd, data)	(cmd | (data & NCP5623_DATA_MASK))
> +
> +struct ncp5623_led {
> +	bool active;
> +	unsigned int led_no;
> +	struct led_classdev ldev;
> +	struct work_struct work;
> +	struct ncp5623_priv *priv;
> +};
> +
> +struct ncp5623_priv {
> +	struct ncp5623_led leds[NCP5623_MAX_LEDS];

Please allocate memory dynamically, depending on the number
of LEDs defined in a Device Tree.

> +	u32 led_iref;
> +	u32 led_max_current;
> +	struct i2c_client *client;
> +};
> +
> +static struct ncp5623_led *ldev_to_led(struct led_classdev *ldev)
> +{
> +	return container_of(ldev, struct ncp5623_led, ldev);
> +}
> +
> +static struct ncp5623_led *work_to_led(struct work_struct *work)
> +{
> +	return container_of(work, struct ncp5623_led, work);
> +}

If you registered brightness_set_blocking op instead of brightness_set,
then the workqueue wouldn't be required in the driver.

> +static int ncp5623_send_cmd(struct ncp5623_priv *priv, u8 cmd, u8 data)
> +{
> +	char cmd_data[1] = { NCP5623_CMD(cmd, data) };
> +	int err;
> +
> +	err = i2c_master_send(priv->client, cmd_data, ARRAY_SIZE(cmd_data));

Please add empty line here.

> +	return (err < 0 ? err : 0);
> +}
> +
> +static int ncp5623_set_pwm(struct ncp5623_led *led, u8 brightness)
> +{
> +	struct ncp5623_priv *priv = led->priv;
> +	u8 cmd;
> +
> +	switch (led->led_no) {
> +	case 0:
> +		cmd = CMD_PWM1;
> +		break;
> +	case 1:
> +		cmd = CMD_PWM2;
> +		break;
> +	case 2:
> +		cmd = CMD_PWM3;
> +		break;
> +	default:
> +		return -EINVAL;
> +	}

Macro for calculating cmd basing on led->led_no would allow
for getting rid of the switch statement.

> +
> +	return ncp5623_send_cmd(priv, cmd, brightness);
> +}
> +
> +static void ncp5623_led_work(struct work_struct *work)
> +{
> +	struct ncp5623_led *led = work_to_led(work);
> +	enum led_brightness brightness = led->ldev.brightness;
> +	int err;
> +
> +	err = ncp5623_set_pwm(led, brightness);
> +
> +	if (err < 0)
> +		dev_err(led->ldev.dev, "failed setting brightness\n");
> +}
> +
> +static void ncp5623_brightness_set(struct led_classdev *led_cdev,
> +				   enum led_brightness brightness)
> +{
> +	struct ncp5623_led *led = ldev_to_led(led_cdev);
> +
> +	led->ldev.brightness = brightness;

This is secured by LED core.

> +	schedule_work(&led->work);
> +}
> +
> +static void ncp5623_destroy_devices(struct ncp5623_priv *priv)
> +{
> +	struct ncp5623_led *led;
> +	int i;
> +
> +	for (i = 0; i < NCP5623_MAX_LEDS; i++) {
> +		led = &priv->leds[i];
> +		if (led->active) {
> +			led_classdev_unregister(&led->ldev);
> +			cancel_work_sync(&led->work);
> +		}
> +	}
> +}
> +
> +static int ncp5623_configure(struct device *dev,
> +			     struct ncp5623_priv *priv)
> +{
> +	unsigned int i;
> +	unsigned int n;
> +	struct ncp5623_led *led;
> +	int err;
> +
> +	/* Compute the value of ILED register to honor led_max_current */
> +	n = 2400 * priv->led_iref / priv->led_max_current + 1;
> +	if (n > NCP5623_MAX_CURRENT)
> +		n = NCP5623_MAX_CURRENT;
> +	n = NCP5623_MAX_CURRENT - n;
> +
> +	dev_dbg(dev, "setting maximum current to %u uA\n",
> +		2400 * priv->led_iref / (NCP5623_MAX_CURRENT - n));
> +
> +	err = ncp5623_send_cmd(priv, CMD_ILED, n);
> +	if (err < 0) {
> +		dev_err(dev, "cannot set the current\n");
> +		return err;
> +	}
> +
> +	/* Setup each individual LED */
> +	for (i = 0; i < NCP5623_MAX_LEDS; i++) {
> +		led = &priv->leds[i];
> +
> +		if (!led->active)
> +			continue;
> +
> +		led->priv = priv;
> +		led->led_no = i;
> +		led->ldev.brightness_set = ncp5623_brightness_set;
> +		led->ldev.max_brightness = NCP5623_MAX_STEPS - 1;

max_brightness should be asserted according to led-max-microamp
property.

> +		INIT_WORK(&led->work, ncp5623_led_work);

Please remove it and use brightness_set_blocking op.

> +		err = led_classdev_register(dev, &led->ldev);

Use devm prefixed version.

> +		if (err < 0) {
> +			dev_err(dev, "couldn't register LED %s\n",
> +				led->ldev.name);
> +			goto exit;
> +		}
> +	}
> +
> +	return 0;
> +
> +exit:
> +	ncp5623_destroy_devices(priv);
> +	return err;
> +}
> +
> +static const struct of_device_id ncp5623_of_match[] = {
> +	{ .compatible = "onnn,ncp5623" },
> +	{ /* sentinel */ },
> +};
> +MODULE_DEVICE_TABLE(of, ncp5623_of_match);
> +
> +static int ncp5623_probe(struct i2c_client *client,
> +			 const struct i2c_device_id *id)
> +{
> +	struct device *dev = &client->dev;
> +	struct device_node *np = dev->of_node, *child;
> +	struct ncp5623_priv *priv;
> +	struct ncp5623_led *led;
> +	u32 reg;
> +	int err, count;
> +
> +	count = of_get_child_count(np);
> +	if (!count || count > NCP5623_MAX_LEDS)
> +		return -EINVAL;

Please separate DT parsing from LED class device registration.
You could add ncp5623_parse_dt(). This is kind of standard.

> +
> +	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->client = client;
> +
> +	i2c_set_clientdata(client, priv);
> +
> +	err = of_property_read_u32(np, "onnn,led-iref-microamp",
> +				   &priv->led_iref);
> +	if (err)
> +		return -EINVAL;
> +	err = of_property_read_u32(np, "led-max-microamp",
> +				   &priv->led_max_current);
> +	if (err || priv->led_max_current > NCP5623_MAX_CURRENT_UA)
> +		return -EINVAL;
> +
> +	for_each_child_of_node(np, child) {
> +		err = of_property_read_u32(child, "reg", &reg);
> +		if (err)
> +			return err;
> +		if (reg < 0 || reg >= NCP5623_MAX_LEDS)
> +			return -EINVAL;

You need to call of_node_put if breaking this loop. Please refer
to the other LED class drivers.

> +		led = &priv->leds[reg];
> +		if (led->active)
> +			return -EINVAL;
> +		led->active = true;
> +		led->ldev.name =
> +			of_get_property(child, "label", NULL) ? : child->name;
> +		led->ldev.default_trigger =
> +			of_get_property(child, "linux,default-trigger", NULL);

Please mention also default-trigger property in the DT documenation.

> +	}
> +	return ncp5623_configure(dev, priv);
> +}
> +
> +static int ncp5623_remove(struct i2c_client *client)
> +{
> +	struct ncp5623_priv *priv = i2c_get_clientdata(client);
> +
> +	ncp5623_destroy_devices(priv);
> +
> +	return 0;
> +}
> +
> +static const struct i2c_device_id ncp5623_id[] = {
> +	{ "ncp5623" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(i2c, ncp5623_id);
> +
> +static struct i2c_driver ncp5623_driver = {
> +	.driver = {
> +		.name = "ncp5623",
> +		.of_match_table = of_match_ptr(ncp5623_of_match),
> +	},
> +	.probe = ncp5623_probe,
> +	.remove = ncp5623_remove,
> +	.id_table = ncp5623_id,
> +};
> +
> +module_i2c_driver(ncp5623_driver);
> +
> +MODULE_AUTHOR("Florian Vaussard <florian.vaussard@...g-vd.ch>");
> +MODULE_LICENSE("GPL");

You mentioned GPL v2 at the top.

> +MODULE_DESCRIPTION("NCP5623 LED driver");
>


-- 
Best regards,
Jacek Anaszewski

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