linux-kernel - Re: [5/5] ARM: tegra: jetson-tk1: enable GK20A GPU

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Date:	Thu, 25 Sep 2014 20:10:31 +0200
From:	Sjoerd Simons <sjoerd@...n.net>
To:	Thierry Reding <thierry.reding@...il.com>
Cc:	Stephen Warren <swarren@...dotorg.org>,
	Alexandre Courbot <acourbot@...dia.com>,
	Ben Skeggs <bskeggs@...hat.com>, nouveau@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
	linux-kernel@...r.kernel.org, gnurou@...il.com
Subject: Re: [5/5] ARM: tegra: jetson-tk1: enable GK20A GPU

On Thu, 2014-09-25 at 18:41 +0200, Thierry Reding wrote:
> On Thu, Sep 25, 2014 at 09:48:01AM -0600, Stephen Warren wrote:
> > On 09/25/2014 07:27 AM, Sjoerd Simons wrote:
> > >Playing a bit with todays linux-next on my jetson, it seems this patch is
> > >still required for enabling the GPU. Is there anything blocking it (firmware
> > >not available yet in liux-firmware?)
> > 
> > I think initially I was waiting for the DRM patch "drm/nouvea: support for
> > probing platform devices" to be applied, but it looks like that's been
> > applied already, so only patches 4 and 5 in this series are still
> > outstanding.
> > 
> > Alex, wasn't there also some issue where the VPR register had to be
> > programmed, and if it wasn't there'd be a hang when the GPU registers were
> > touched? If we've added code to Nouveau/tegradrm to detect that and avoid
> > the problem, then I guess we can commit these last two patches for 3.19. A
> > resend after the 3.18 merge window might help.
> 
> A patch that programs VPR was merged into U-Boot (though I don't think
> it's made it into master yet).

Assuming you're talking about "ARM: tegra: Disable VPR",that has landed
in u-boot master and released as part of v2014.10-rc2 [0]

>  I'm not sure we can reasonably check for
> that in Nouveau, given that the register is somewhere completely
> unrelated. In fact I think the U-Boot patch was triggered by some
> discussion about how to solve this and it was decided that it shouldn't
> be done in the kernel, but U-Boot should set it up.
> 
> That said, perhaps one solution would be to make U-Boot enable the gk20a
> device if it's set up the VPR and disable it otherwise?

I guess in that case the vdd-supply should still be added to the dts
with u-boot toggling the status field of the node?


0: http://git.denx.de/?p=u-boot.git;a=commit;h=df3443dfa449ad02bef8ddf6e2c90a6fd9394fc9
-- 
Sjoerd Simons <sjoerd@...n.net>
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