linux-kernel - Re: [PATCH 02/13] drm/panel: ilitek-ili9881c: move display_on/

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Message-ID: <16537c3f-824a-4268-a51e-5efc88a671bf@linaro.org>
Date: Mon, 4 Aug 2025 17:15:41 +0200
From: neil.armstrong@...aro.org
To: Heiko Stuebner <heiko@...ech.de>
Cc: quic_jesszhan@...cinc.com, maarten.lankhorst@...ux.intel.com,
 mripard@...nel.org, tzimmermann@...e.de, robh@...nel.org,
 krzk+dt@...nel.org, conor+dt@...nel.org, hjc@...k-chips.com,
 andy.yan@...k-chips.com, andyshrk@....com, nicolas.frattaroli@...labora.com,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH 02/13] drm/panel: ilitek-ili9881c: move display_on/_off
 dcs calls to (un-)prepare

On 07/07/2025 18:48, Heiko Stuebner wrote:
> At least for panel-bridges, the atomic_enable call is defined as being
> called right after the preceding element in the display pipe is enabled.
> 
> It is also stated that "The bridge can assume that the display pipe (i.e.
> clocks and timing signals) feeding it is running when this callback is
> called"
> 
> This means the DSI controller driving this display would have already
> switched over to video-mode from command mode and thus dcs functions
> should not be called anymore at this point.
> 
> This caused a non-working display for me, when trying to enable
> the rk3576 dsi controller using a display using this controller.
> 
> Therefore move the display_on/off calls the more appropriate
> prepare/unprepare callbacks.
> 
> Signed-off-by: Heiko Stuebner <heiko@...ech.de>
> ---
>   drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 27 +++++--------------
>   1 file changed, 7 insertions(+), 20 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> index d7a17dca2a9c..a20b52181ea0 100644
> --- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> @@ -1315,35 +1315,24 @@ static int ili9881c_prepare(struct drm_panel *panel)
>   	if (ret)
>   		goto disable_power;
>   
> -	return 0;
> -
> -disable_power:
> -	regulator_disable(ctx->power);
> -	return ret;
> -}
> -
> -static int ili9881c_enable(struct drm_panel *panel)
> -{
> -	struct ili9881c *ctx = panel_to_ili9881c(panel);
> -
>   	msleep(120);
>   
> -	mipi_dsi_dcs_set_display_on(ctx->dsi);
> +	ret = mipi_dsi_dcs_set_display_on(ctx->dsi);
> +	if (ret)
> +		goto disable_power;
>   
>   	return 0;
> -}
>   
> -static int ili9881c_disable(struct drm_panel *panel)
> -{
> -	struct ili9881c *ctx = panel_to_ili9881c(panel);
> -
> -	return mipi_dsi_dcs_set_display_off(ctx->dsi);
> +disable_power:
> +	regulator_disable(ctx->power);
> +	return ret;
>   }
>   
>   static int ili9881c_unprepare(struct drm_panel *panel)
>   {
>   	struct ili9881c *ctx = panel_to_ili9881c(panel);
>   
> +	mipi_dsi_dcs_set_display_off(ctx->dsi);
>   	mipi_dsi_dcs_enter_sleep_mode(ctx->dsi);
>   	regulator_disable(ctx->power);
>   	gpiod_set_value_cansleep(ctx->reset, 1);
> @@ -1499,8 +1488,6 @@ static enum drm_panel_orientation ili9881c_get_orientation(struct drm_panel *pan
>   static const struct drm_panel_funcs ili9881c_funcs = {
>   	.prepare	= ili9881c_prepare,
>   	.unprepare	= ili9881c_unprepare,
> -	.enable		= ili9881c_enable,
> -	.disable	= ili9881c_disable,
>   	.get_modes	= ili9881c_get_modes,
>   	.get_orientation = ili9881c_get_orientation,
>   };

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