linux-kernel - Re: [PATCH 1/2] ARM: tegra: venice2: add GK20A GPU DT node

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Date:	Thu, 9 Oct 2014 10:00:18 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Alexandre Courbot <acourbot@...dia.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
	gnurou@...il.com, Thierry Reding <treding@...dia.com>
Subject: Re: [PATCH 1/2] ARM: tegra: venice2: add GK20A GPU DT node

On Thu, Oct 09, 2014 at 04:48:56PM +0900, Alexandre Courbot wrote:
> On 10/09/2014 04:43 PM, Thierry Reding wrote:
> >* PGP Signed by an unknown key
> >
> >On Thu, Oct 09, 2014 at 03:11:51PM +0900, Alexandre Courbot wrote:
> >>From: Thierry Reding <treding@...dia.com>
> >>
> >>Add the device-tree node for the GK20A GPU and leave it disabled by
> >>default. It is the responsability of the bootloader to enable it if the
> >>VPR registers have been programmed such as the GPU can operate.
> >>
> >>Signed-off-by: Thierry Reding <treding@...dia.com>
> >>Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> >>---
> >>  arch/arm/boot/dts/tegra124-venice2.dts | 8 +++++++-
> >>  1 file changed, 7 insertions(+), 1 deletion(-)
> >
> >Are you going to send the corresponding patches for U-Boot to update
> >the status property if it's initialized VPR?
> 
> Yes. But maybe I should wait until upstream Nouveau actually works properly
> for that? Right now it will probe successfully, but will crash as soon as
> the GPU is used because there still are memory coherency problems.

I think the same really goes for these patches. Applying these will make
the node available to U-Boot, so technically some future U-Boot version
could modify a kernel DTB and boot a version where nouveau didn't yet
work out-of-the-box.

There's also still the issue about firmware loading and so on, so maybe
holding off on applying these patches until gk20a is fully enabled is a
good idea. Normally I guess this would be done by not adding the kernel
driver until it's expected to be at least usable to some degree, but I
guess it is a bit late for that now.

Thierry

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