From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter De Schrijver Subject: Re: [PATCH 0/3] drm/gk20a: support for reclocking Date: Thu, 10 Jul 2014 12:43:00 +0300 Message-ID: <20140710094300.GP23218@tbergstrom-lnx.Nvidia.com> References: <1404977677-22248-1-git-send-email-acourbot@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Return-path: Content-Disposition: inline In-Reply-To: <1404977677-22248-1-git-send-email-acourbot-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Alexandre Courbot Cc: Ben Skeggs , "nouveau-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" , "dri-devel-PD4FTy7X32lNgt0PjOBp9y5qC8QIuHrW@public.gmane.org" , "linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , "gnurou-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org" List-Id: nouveau.vger.kernel.org On Thu, Jul 10, 2014 at 09:34:34AM +0200, Alexandre Courbot wrote: > This series adds support for reclocking on GK20A. The first two patches touch > the clock subsystem to allow GK20A to operate, by making the presence of the > thermal and voltage devices optional, and allowing pstates to be provided > directly instead of being probed using the BIOS (which Tegra does not have). > > The last patch adds the GK20A clock device. Arguably the clock can be seen as a > stripped-down version of what is seen on NVE0, however instead of using NVE0 > support has been written from scratch using the ChromeOS kernel as a basis. > There are several reasons for this: > > - The ChromeOS driver uses a lookup table for the P coefficient which I could > not find in the NVE0 driver, > - Some registers that NVE0 expects to find are not present on GK20A (e.g. > 0x137120 and 0x137140), > - Calculation of MNP is done differently from what is performed in > nva3_pll_calc(), and it might be interesting to compare the two methods, > - All the same, the programming sequence is done differently in the ChromeOS > driver and NVE0 could possibly benefit from it (?) > > It would be interesting to try and merge both, but for now I prefer to have the > two coexisting to ensure proper operation on GK20A and besure I don't break > dGPU support. :) > > Regarding the first patch, one might argue that I could as well add thermal > and voltage devices to GK20A. The reason this is not done is because these > currently depend heavily on the presence of a BIOS, and will require a rework > similar to that done in patch 2 for clocks. I would like to make sure this > approach is approved because applying it to other subdevs. I think this should use CCF so we can use pre and post rate change notifiers to hookup vdd_gpu DVS. Thanks, Peter.