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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <6e886700-24a8-4127-9324-7245b6cbf6b7@gmail.com>
Date: Tue, 16 Sep 2025 17:28:49 +0200
From: Emanuele Ghidoli <ghidoliemanuele@...il.com>
To: Doug Anderson <dianders@...omium.org>
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



On 16/09/2025 16:45, Doug Anderson wrote:
> 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

Hi Doug,
thanks for the test.
According to the datasheet, LP is recommended for the front porch and optional
for the back porch.
Could you please run another test by keeping only MIPI_DSI_MODE_VIDEO_NO_HFP
and removing MIPI_DSI_MODE_VIDEO_NO_HBP?

dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_NO_HFP;

Kind regards,
Emanuele