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

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Message-ID: <2007957.usQuhbGJ8B@steina-w>
Date: Thu, 17 Oct 2024 08:50:43 +0200
From: Alexander Stein <alexander.stein@...tq-group.com>
To: Stefan Agner <stefan@...er.ch>, Alison Wang <alison.wang@....com>, David Airlie <airlied@...il.com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, Simona Vetter <simona@...ll.ch>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Daniel Vetter <daniel@...ll.ch>, Matthias Schiffer <matthias.schiffer@...group.com>, Thomas Zimmermann <tzimmermann@...e.de>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] drm: fsl-dcu: enable PIXCLK on LS1021A

Hi everyone,

Am Freitag, 27. September 2024, 01:13:57 CEST schrieb Dmitry Baryshkov:
> On Thu, Sep 26, 2024 at 04:09:03PM GMT, Alexander Stein wrote:
> > 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.
> 
> My bet was on the firmware, but I never touched Layerscape platforms.
> Anyway,
> 
> Fixes: 109eee2f2a18 ("drm/layerscape: Add Freescale DCU DRM driver")
> Acked-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

Any additional feedback?

Best regards,
Alexander
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