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

From: Stephen Warren
Date: Thu Sep 25 2014 - 14:06:43 EST

On 09/25/2014 10:41 AM, 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

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). 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?

For that to work, we'd need the DT to say status="disabled" by default for the GPU, and for the fixed U-Boot (and indeed every other bootloader...) to enable the GPU node. This would allow people with old versions of U-Boot (or other bootloaders) to continue to boot. This means bootloaders would only have to set status="okay", but never have to set status="disabled", which at least simplifies them a tiny bit.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at