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 >> 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). 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.
