linux-kernel - Re: [PATCH v2 2/4] video: ssd1307fb: Do not hard code active-low reset sequence

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Date:   Thu, 20 Dec 2018 13:33:59 +0100
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Vokáč Michal <Michal.Vokac@...ft.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Fabio Estevam <fabio.estevam@....com>,
        Maxime Ripard <maxime.ripard@...tlin.com>,
        "linux-fbdev@...r.kernel.org" <linux-fbdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] video: ssd1307fb: Do not hard code active-low
 reset sequence

On 20/12/2018 12:13:55+0000, Vokáč Michal wrote:
> The SSD130x OLED display reset signal is active low. Now the reset
> sequence is implemented in such a way that users are forced to
> define reset-gpios as GPIO_ACTIVE_HIGH in DT to make the reset work.
> 
> Do not hard code the active-low sequence into the driver but instead
> allow the user to specify the gpio as GPIO_ACTIVE_LOW to reflect
> the real world.
> 
> Reviewed-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Michal Vokáč <michal.vokac@...ft.com>
Reviewed-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

> ---
> Changes from v1:
>  - Add R-by from Rob
> 
>  drivers/video/fbdev/ssd1307fb.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/video/fbdev/ssd1307fb.c b/drivers/video/fbdev/ssd1307fb.c
> index 4061a20..3b361bc 100644
> --- a/drivers/video/fbdev/ssd1307fb.c
> +++ b/drivers/video/fbdev/ssd1307fb.c
> @@ -667,10 +667,10 @@ static int ssd1307fb_probe(struct i2c_client *client,
>  
>  	if (par->reset) {
>  		/* Reset the screen */
> -		gpiod_set_value_cansleep(par->reset, 0);
> -		udelay(4);
>  		gpiod_set_value_cansleep(par->reset, 1);
>  		udelay(4);
> +		gpiod_set_value_cansleep(par->reset, 0);
> +		udelay(4);
>  	}
>  
>  	if (par->vbat_reg) {
> -- 
> 2.1.4
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com