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

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Date:	Fri, 26 Sep 2014 12:01:03 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Sjoerd Simons <sjoerd@...n.net>
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, Sep 25, 2014 at 08:10:31PM +0200, Sjoerd Simons wrote:
> 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]

Oh, good.

> >  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?

Yes, if that's what we decide on then this patch should be modified to
remove the status = "okay" line.

Thierry

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