linux-kernel - Re: [PATCH v1] gpu: host1x: Ignore clients initialization failure

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Date:   Fri, 3 Aug 2018 12:50:55 +0200
From:   Thierry Reding <thierry.reding@...il.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Mikko Perttunen <cyndis@...si.fi>, Kyle Evans <kvans32@...il.com>,
        linux-tegra@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] gpu: host1x: Ignore clients initialization failure

On Wed, Aug 01, 2018 at 06:08:07PM +0300, Dmitry Osipenko wrote:
> From time to time new bugs are popping up, causing some host1x client to
> fail its initialization. Currently a single clients initialization failure
> causes whole host1x device registration to fail, as a result a single DRM
> sub-device initialization failure makes whole DRM initialization to fail.
> Let's ignore clients initialization failure, as a result display panel
> lights up even if some DRM clients (say GR2D or VIC) fail to initialize.
> 
> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
> ---
>  drivers/gpu/host1x/bus.c | 18 +++++++-----------
>  1 file changed, 7 insertions(+), 11 deletions(-)

This is actually done on purpose. I can't think of a case where we would
actively like to keep a half-broken DRM device operational. The errors
that you're talking about should only happen during development, and the
device not showing up is a pretty good indicator that something is wrong
as opposed to everything booting normally and then getting some cryptic
error at runtime because one of the clients didn't initialize.

From my perspective, all clients should always be operational in
whatever baseline version you use. If it isn't that's a bug that should
be fixed. Ideally those bugs should get fixed before making it into a
baseline version (mainline, linux-next, ...), so that this never impacts
even developers, unless they break it themselves, in which case refusing
to register the DRM device is a pretty good incentive to fix it.

Thierry

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