linux-kernel - Re: [PATCH v4 4/5] drm/panel: samsung-s6e88a0-ams427ap24: Add brightness control

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Message-ID: <CACRpkdZfJqhUFrpv7BmMiuQYJJ8dveJyaKVh9dpVYbz-QDnKGg@mail.gmail.com>
Date: Mon, 28 Oct 2024 13:47:09 +0100
From: Linus Walleij <linus.walleij@...aro.org>
To: Jakob Hauser <jahau@...ketmail.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Thierry Reding <thierry.reding@...il.com>, 
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, dri-devel@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	~postmarketos/upstreaming@...ts.sr.ht
Subject: Re: [PATCH v4 4/5] drm/panel: samsung-s6e88a0-ams427ap24: Add
 brightness control

On Mon, Oct 28, 2024 at 12:42 AM Jakob Hauser <jahau@...ketmail.com> wrote:

> The tables for brightness to candela, aid and elvss were taken from downstream
> kernel file "dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi" [1][2][3].
>
> The gamma table gets generated in "ss_dsi_smart_dimming_S6E88A0_AMS427AP24.c" [4]
> with hard-coded starting values. The function smart_dimming_init() [5] goes
> through the v{*}_adjustments, generate_gray_scale and gamma_init procedure.
> Instead of calculating it manually, it's easier to compile a custom downstream
> kernel with SMART_DIMMING_DEBUG enabled and read out dmesg early at boot.
>
> Selection of the values for aid and elvss are again according to downstream
> file "dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi" [6][7].
>
> The set of write commands is guided by downstream file "ss_dsi_panel_common.c" [8]
> followed by "ss_dsi_panel_S6E88A0_AMS427AP24.c" [9].
>
> The dsi mode flag MIPI_DSI_MODE_VIDEO_NO_HFP prevents screen flickering while
> changing the brightness.
>
> [1] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi#L341-L397
> [2] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi#L214-L254
> [3] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi#L301-L320
> [4] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/ss_dsi_smart_dimming_S6E88A0_AMS427AP24.c
> [5] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/ss_dsi_smart_dimming_S6E88A0_AMS427AP24.c#L1816-L1900
> [6] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi#L256-L268
> [7] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/dsi_panel_S6E88A0_AMS427AP24_qhd_octa_video.dtsi#L322-L334
> [8] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/ss_dsi_panel_common.c#L1389-L1517
> [9] https://github.com/msm8916-mainline/linux-downstream/blob/GT-I9195I/drivers/video/msm/mdss/samsung/S6E88A0_AMS427AP24/ss_dsi_panel_S6E88A0_AMS427AP24.c#L666-L678
>
> Signed-off-by: Jakob Hauser <jahau@...ketmail.com>
> Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>

Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij