linux-kernel - Re: [PATCH v7 4/8] drm/panel: sw43408: Separate reset sequence into own function

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Message-ID: <6c04c58e-339b-4b5c-a2b4-8a9509612335@linaro.org>
Date: Tue, 16 Dec 2025 10:53:37 +0100
From: Neil Armstrong <neil.armstrong@...aro.org>
To: david@...t.cz, Bjorn Andersson <andersson@...nel.org>,
 Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>,
 Casey Connolly <casey.connolly@...aro.org>,
 Jessica Zhang <jesszhan0024@...il.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Marijn Suijten <marijn.suijten@...ainline.org>,
 Dmitry Baryshkov <lumag@...nel.org>, Vinod Koul <vkoul@...nel.org>,
 Petr Hodina <phodina@...tonmail.com>,
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v7 4/8] drm/panel: sw43408: Separate reset sequence into
 own function

On 12/14/25 15:51, David Heidelberg via B4 Relay wrote:
> From: David Heidelberg <david@...t.cz>
> 
> Splitting reset() from prepare() follows clean coding practices and lets
> us potentially make reset optional in the future for flicker-less
> takeover from a bootloader or framebuffer driver where the panel is
> already configured.
> 
> Signed-off-by: David Heidelberg <david@...t.cz>
> ---
>   drivers/gpu/drm/panel/panel-lg-sw43408.c | 17 +++++++++++------
>   1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-lg-sw43408.c b/drivers/gpu/drm/panel/panel-lg-sw43408.c
> index dcca7873acf8e..ed9c7452ea846 100644
> --- a/drivers/gpu/drm/panel/panel-lg-sw43408.c
> +++ b/drivers/gpu/drm/panel/panel-lg-sw43408.c
> @@ -119,6 +119,16 @@ static int sw43408_program(struct drm_panel *panel)
>   	return ctx.accum_err;
>   }
>   
> +static void sw43408_reset(struct sw43408_panel *ctx)
> +{
> +	gpiod_set_value(ctx->reset_gpio, 0);
> +	usleep_range(9000, 10000);
> +	gpiod_set_value(ctx->reset_gpio, 1);
> +	usleep_range(1000, 2000);
> +	gpiod_set_value(ctx->reset_gpio, 0);
> +	usleep_range(9000, 10000);
> +}
> +
>   static int sw43408_prepare(struct drm_panel *panel)
>   {
>   	struct sw43408_panel *ctx = to_panel_info(panel);
> @@ -130,12 +140,7 @@ static int sw43408_prepare(struct drm_panel *panel)
>   
>   	usleep_range(5000, 6000);
>   
> -	gpiod_set_value(ctx->reset_gpio, 0);
> -	usleep_range(9000, 10000);
> -	gpiod_set_value(ctx->reset_gpio, 1);
> -	usleep_range(1000, 2000);
> -	gpiod_set_value(ctx->reset_gpio, 0);
> -	usleep_range(9000, 10000);
> +	sw43408_reset(ctx);
>   
>   	ret = sw43408_program(panel);
>   	if (ret)
> 

Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>