linux-kernel - Re: [PATCH v4 1/5] pwm-backlight: enable/disable the PWM before/after LCD enable toggle.

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Message-ID: <3e986794-f09c-b1be-6b28-ab33befdc64f@linaro.org>
Date:   Mon, 24 Jul 2017 16:13:55 +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 v4 1/5] pwm-backlight: enable/disable the PWM before/after
 LCD enable toggle.

On 21/07/17 11:48, Enric Balletbo i Serra wrote:
> Before this patch the enable signal was set before the PWM signal and
> vice-versa on power off. This sequence is wrong, at least, it is on
> the different panels datasheets that I checked, so I inverted the sequence
> to follow the specs.
> 
> For reference the following panels have the mentioned sequence:
>    - N133HSE-EA1 (Innolux)
>    - N116BGE (Innolux)
>    - N156BGE-L21 (Innolux)
>    - B101EAN0 (Auo)
>    - B101AW03 (Auo)
>    - LTN101NT05 (Samsung)
>    - CLAA101WA01A (Chunghwa)
> 
> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>

Acked-by: Daniel Thompson <daniel.thompson@...aro.org>

> ---
> Changes since v3:
>   - List the part numbers for the panel checked (Daniel Thompson)
> Changes since v2:
>   - Add this as a separate patch (Thierry Reding)
> Changes since v1:
>   - None
> 
>   drivers/video/backlight/pwm_bl.c | 9 +++++----
>   1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
> index 002f1ce..909a686 100644
> --- a/drivers/video/backlight/pwm_bl.c
> +++ b/drivers/video/backlight/pwm_bl.c
> @@ -54,10 +54,11 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb, int brightness)
>   	if (err < 0)
>   		dev_err(pb->dev, "failed to enable power supply\n");
>   
> +	pwm_enable(pb->pwm);
> +
>   	if (pb->enable_gpio)
>   		gpiod_set_value_cansleep(pb->enable_gpio, 1);
>   
> -	pwm_enable(pb->pwm);
>   	pb->enabled = true;
>   }
>   
> @@ -66,12 +67,12 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb)
>   	if (!pb->enabled)
>   		return;
>   
> -	pwm_config(pb->pwm, 0, pb->period);
> -	pwm_disable(pb->pwm);
> -
>   	if (pb->enable_gpio)
>   		gpiod_set_value_cansleep(pb->enable_gpio, 0);
>   
> +	pwm_config(pb->pwm, 0, pb->period);
> +	pwm_disable(pb->pwm);
> +
>   	regulator_disable(pb->power_supply);
>   	pb->enabled = false;
>   }
>