linux-kernel - Re: [PATCH v3 3/5] pwm-backlight: add support for PWM delays proprieties.

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Message-ID: <d38fa016-ea9c-edf8-9684-5c1235d27c82@linaro.org>
Date:   Tue, 18 Jul 2017 10:38:19 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Rob Herring <robh+dt@...nel.org>, Pavel Machek <pavel@....cz>,
        Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Heiko Stuebner <heiko@...ech.de>
Cc:     linux-pwm@...r.kernel.org, linux-fbdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 3/5] pwm-backlight: add support for PWM delays
 proprieties.

On 17/07/17 22:28, Enric Balletbo i Serra wrote:
> Some panels (i.e. N116BGE-L41), in their power sequence specifications,
> request a delay between set the PWM signal and enable the backlight and
> between clear the PWM signal and disable the backlight. Add support for
> the new post-pwm-on-delay-us and pwm-off-delay-us proprieties to meet
> the timings.
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> ---
> Changes since v2:
>   - Move the pwm/enable sequence to another patch (Thierry Reding)
> Changes since v1:
>   - As suggested by Daniel Thompson
>     - Do not assume power-on delay and power-off delay will be the same
>   - Move the check of dt property to the parse dt function.
> 
>   drivers/video/backlight/pwm_bl.c | 17 +++++++++++++++++
>   include/linux/pwm_backlight.h    |  1 +
>   2 files changed, 18 insertions(+)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 909a686..528155d 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -10,6 +10,7 @@
>    * published by the Free Software Foundation.
>    */
>   
> +#include <linux/delay.h>
>   #include <linux/gpio/consumer.h>
>   #include <linux/gpio.h>
>   #include <linux/module.h>
> @@ -35,6 +36,7 @@ struct pwm_bl_data {
>   	struct gpio_desc	*enable_gpio;
>   	unsigned int		scale;
>   	bool			legacy;
> +	unsigned int		pwm_delay[2];

Two named members would be better here (eliminating the "magic" 0 and 1).


>   	int			(*notify)(struct device *,
>   					  int brightness);
>   	void			(*notify_after)(struct device *,
> @@ -56,6 +58,9 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
>   
>   	pwm_enable(pb->pwm);
>   
> +	if (pb->pwm_delay[0])
> +		usleep_range(pb->pwm_delay[0], pb->pwm_delay[0] * 2);
> +
>   	if (pb->enable_gpio)
>   		gpiod_set_value_cansleep(pb->enable_gpio, 1);
>   
> @@ -70,6 +75,9 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
>   	if (pb->enable_gpio)
>   		gpiod_set_value_cansleep(pb->enable_gpio, 0);
>   
> +	if (pb->pwm_delay[1])
> +		usleep_range(pb->pwm_delay[1], pb->pwm_delay[1] * 2);
> +
>   	pwm_config(pb->pwm, 0, pb->period);
>   	pwm_disable(pb->pwm);
>   
> @@ -175,6 +183,14 @@ static int pwm_backlight_parse_dt(struct device *dev,
>   		data->max_brightness--;
>   	}
>   
> +	/*
> +	 * These values are optional and set as 0 by default, the out values
> +	 * are modified only if a valid u32 value can be decoded.
> +	 */
> +	of_property_read_u32(node, "post-pwm-on-delay-us",
> +			     &data->pwm_delay[0]);
> +	of_property_read_u32(node, "pwm-off-delay-us", &data->pwm_delay[1]);
> +
>   	data->enable_gpio = -EINVAL;
>   	return 0;
>   }
> @@ -273,6 +289,7 @@ static int pwm_backlight_probe(struct platform_device *pdev)
>   	pb->exit = data->exit;
>   	pb->dev = &pdev->dev;
>   	pb->enabled = false;
> +	memcpy(pb->pwm_delay, data->pwm_delay, sizeof(pb->pwm_delay));
>   
>   	pb->enable_gpio = devm_gpiod_get_optional(&pdev->dev, "enable",
>   						  GPIOD_ASIS);
> diff --git a/include/linux/pwm_backlight.h b/include/linux/pwm_backlight.h
> index efdd922..bf37131 100644
> --- a/include/linux/pwm_backlight.h
> +++ b/include/linux/pwm_backlight.h
> @@ -13,6 +13,7 @@ struct platform_pwm_backlight_data {
>   	unsigned int lth_brightness;
>   	unsigned int pwm_period_ns;
>   	unsigned int *levels;
> +	unsigned int pwm_delay[2];
>   	/* TODO remove once all users are switched to gpiod_* API */
>   	int enable_gpio;
>   	int (*init)(struct device *dev);
>