linux-kernel - Re: [Nouveau] [PATCH] drm/nouveau/bar/gk20a: Avoid bar teardown during init

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Date:   Wed, 10 Jan 2018 13:20:32 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Ben Skeggs <bskeggs@...hat.com>, David Airlie <airlied@...ux.ie>,
        nouveau@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Guillaume Tucker <guillaume.tucker@...labora.com>
Subject: Re: [Nouveau] [PATCH] drm/nouveau/bar/gk20a: Avoid bar teardown
 during init

On Thu, Jan 04, 2018 at 11:29:09AM +0000, Jon Hunter wrote:
> Commit bbb163e18960 ("drm/nouveau/bar: implement bar1 teardown")
> introduced add a teardown helper function for BAR1. During
> initialisation of the Nouveau, initially all the teardown helpers are
> called once, before calling their init counterparts. For gk20a, after
> the BAR1 teardown function is called, the device is hanging during the
> initialisation of the FB sub-device. At this point it is unclear why
> this is happening and this is still under investigation. However, this
> change is preventing Tegra124 devices from booting when Nouveau is
> enabled. To allow Tegra124 to boot, remove the teardown helper for
> gk20a.
> 
> This is based upon a previous patch by Guillaume Tucker but limits
> the workaround to only gk20a GPUs.
> 
> Fixes: bbb163e18960 ("drm/nouveau/bar: implement bar1 teardown")
> Reported-by: Guillaume Tucker <guillaume.tucker@...labora.com>
> Signed-off-by: Jon Hunter <jonathanh@...dia.com>
> ---
> I am not happy that we do not yet fully understand the cause of
> the hang, but I am talking with a few people at NVIDIA about this
> and have a few things to look into. However, given that we are
> close to v4.15 being released and I am not sure we will have a
> proper fix in place before, I think it is best to workaround
> this for now.
> 
>  drivers/gpu/drm/nouveau/nvkm/subdev/bar/base.c  | 3 ++-
>  drivers/gpu/drm/nouveau/nvkm/subdev/bar/gk20a.c | 1 -
>  2 files changed, 2 insertions(+), 2 deletions(-)

Acked-by: Thierry Reding <treding@...dia.com>

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