linux-kernel - Re: [PATCH v2 2/2] drm: fsl-dcu: enable PIXCLK on LS1021A

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Message-ID: <2754373.mvXUDI8C0e@steina-w>
Date: Thu, 26 Sep 2024 16:09:03 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Stefan Agner <stefan@...er.ch>, Alison Wang <alison.wang@....com>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, Matthias Schiffer <matthias.schiffer@...group.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, Simona Vetter <simona@...ll.ch>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] drm: fsl-dcu: enable PIXCLK on LS1021A

Hi Dmitry,

Am Donnerstag, 26. September 2024, 08:05:56 CEST schrieb Dmitry Baryshkov:
> On Thu, Sep 26, 2024 at 07:55:51AM GMT, Alexander Stein wrote:
> > From: Matthias Schiffer <matthias.schiffer@...group.com>
> > 
> > The PIXCLK needs to be enabled in SCFG before accessing certain DCU
> > registers, or the access will hang. For simplicity, the PIXCLK is enabled
> > unconditionally, resulting in increased power consumption.
> 
> By this description it looks like a fix. What is the first broken
> commit? It needs to be mentioned in the Fixes: tag. Or is it hat
> existing devices have been enabling SCFG in some other way?

We discussed this internally and it seems this never worked, unless PIXCLK
was already enabled in SCFG by a different way, e.g. firmware, etc.

Best regards,
Alexander

> > 
> > Signed-off-by: Matthias Schiffer <matthias.schiffer@...group.com>
> > Signed-off-by: Alexander Stein <alexander.stein@...tq-group.com>
> > ---
> > Changes in v2:
> > * Add note about power consumption in commit message
> > * Add note about power consumption in comment
> > * Fix alignment
> > 
> 
> 


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