linux-kernel - Re: [PATCH 2/2] drm/bridge: samsung-dsim: Fix porch calcalcuation rounding

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Message-ID: <e2688a01-47d2-4f89-ab92-252f378d37ba@kontron.de>
Date: Mon, 29 Jan 2024 09:17:48 +0100
From: Frieder Schrempf <frieder.schrempf@...tron.de>
To: Adam Ford <aford173@...il.com>, dri-devel@...ts.freedesktop.org
Cc: aford@...conembedded.com, Inki Dae <inki.dae@...sung.com>,
 Jagan Teki <jagan@...rulasolutions.com>,
 Marek Szyprowski <m.szyprowski@...sung.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>, Daniel Vetter <daniel@...ll.ch>,
 Michael Tretter <m.tretter@...gutronix.de>,
 Marco Felsch <m.felsch@...gutronix.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] drm/bridge: samsung-dsim: Fix porch calcalcuation
 rounding

On 25.01.24 19:44, Adam Ford wrote:
> On Mon, Dec 11, 2023 at 9:33 PM Adam Ford <aford173@...il.com> wrote:
>>
>> When using video sync pulses, the HFP, HBP, and HSA are divided between
>> the available lanes if there is more than one lane.  For certain
>> timings and lane configurations, the HFP may not be evenly divisible.
>> If the HFP is rounded down, it ends up being too small which can cause
>> some monitors to not sync properly. In these instances, adjust htotal
>> and hsync to round the HFP up, and recalculate the htotal.
>>
>> Tested-by: Frieder Schrempf <frieder.schrempf@...tron.de> # Kontron BL i.MX8MM with HDMI monitor
>> Signed-off-by: Adam Ford <aford173@...il.com>
> 
> Gentle nudge on this one.  Basically this fixes an issue with the 8MP,
> but it's still unknown why it doesn't work on 8MM or 8MN, but Frieder
> confirmed there are no regressions on 8MM or 8MN.

I only tested two specific display setups on i.MX8MM. So of course I
can't confirm the absence of regressions in general.

Anyway, I think this should be applied.