linux-kernel - Re: [PATCH v1] drm/bridge: ti-sn65dsi86: Transition to LP mode on every video line

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Message-ID: <CAD=FV=Uftrv=x6CuG7edLCSAi16Kv=ka7qxPViuLM=BEG8pC3Q@mail.gmail.com>
Date: Tue, 16 Sep 2025 07:45:59 -0700
From: Doug Anderson <dianders@...omium.org>
To: Emanuele Ghidoli <ghidoliemanuele@...il.com>
Cc: Emanuele Ghidoli <emanuele.ghidoli@...adex.com>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...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>, 
	Jayesh Choudhary <j-choudhary@...com>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] drm/bridge: ti-sn65dsi86: Transition to LP mode on
 every video line

Hi,

On Tue, Sep 16, 2025 at 7:22 AM Emanuele Ghidoli
<ghidoliemanuele@...il.com> wrote:
>
> From: Emanuele Ghidoli <emanuele.ghidoli@...adex.com>
>
> The component datasheet recommends, to reduce power consumption,
> transitioning to LP mode on every video line.
>
> Enable the MIPI_DSI_MODE_VIDEO_NO_HFP and MIPI_DSI_MODE_VIDEO_NO_HBP
> flags so that the bridge can enter LP mode during the horizontal front
> porch and back porch periods.
>
> Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@...adex.com>
> ---
> Cc: Douglas Anderson <dianders@...omium.org>
> Cc: Andrzej Hajda <andrzej.hajda@...el.com>
> Cc: Neil Armstrong <neil.armstrong@...aro.org>
> Cc: Robert Foss <rfoss@...nel.org>
> Cc: Laurent Pinchart <Laurent.pinchart@...asonboard.com>
> Cc: Jonas Karlman <jonas@...boo.se>
> Cc: Jernej Skrabec <jernej.skrabec@...il.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
> Cc: Maxime Ripard <mripard@...nel.org>
> Cc: Thomas Zimmermann <tzimmermann@...e.de>
> Cc: David Airlie <airlied@...il.com>
> Cc: Simona Vetter <simona@...ll.ch>
> Cc: Jayesh Choudhary <j-choudhary@...com>
> Cc: <dri-devel@...ts.freedesktop.org>
> Cc: <linux-kernel@...r.kernel.org>
> ---
>  drivers/gpu/drm/bridge/ti-sn65dsi86.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

I put this on a sc7180-trogdor based Chromebook and the display no
longer comes up. I don't personally know the MIPI side of the spec too
well so I have no idea why that would be.

-Doug