Re: [igt PATCH] igt/pm_rps: Remove remaining assert on CUR <= MAX

[Jeff McGee <jeff.mcgee@intel.com>]

On Wed, Jun 21, 2017 at 12:55:42PM +0300, Arkadiusz Hiler wrote:
> On Tue, Jun 20, 2017 at 06:15:52PM +0300, Arkadiusz Hiler wrote:
> > On Tue, Jun 20, 2017 at 01:54:54PM +0000, Szwichtenberg, Radoslaw wrote:
> > > On Wed, 2017-06-14 at 12:44 -0700, jeff.mcgee@intel.com wrote:
> > > > From: Jeff McGee <jeff.mcgee@intel.com>
> > > > 
> > > > This completes the change started by:
> > > > 
> > > > commit 39cccab83b7c515a2b57abe679a8cb304c8933ef
> > > > Author: Chris Wilson <chris@chris-wilson.co.uk>
> > > > Date:   Fri May 19 09:41:40 2017 +0100
> > > > 
> > > >     igt/pm_rps: Allow CUR to be greater than MAX (overclocking)
> > > > 
> > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
> > > Reviewed-by: Radoslaw Szwichtenberg <radoslaw.szwichtenberg@intel.com>
> > 
> > Pushed. Thanks for the patch and the review.
> > 
> > Excerpt from CONTRIBUTING:
> > -----------------------------------------------------------------------------
> > Please use --subject-prefix="PATCH i-g-t" so that i-g-t patches are easily
> > identified in the massive amount mails on intel-gfx. To ensure this is always
> > done, autogen.sh will run:
> > 
> >   git config format.subjectprefix "PATCH i-g-t"
> > 
> > on its first invocation.
> > -----------------------------------------------------------------------------
> > 
> > Lack of proper prefix breaks filtering / patchwork and makes changes
> > harder to track, and effectilvely it takes longer to get the patch in.
> > 
> > The autogen.sh thing is a recent addition.
> 
> Hey Jeff,
> 
> The change has been reverted.
> 
> At first the it looked like a sensible folloup to previous changes and
> it even got r-bed, but as pointed out by Michal, this constraint still
> should hold, as it's checked in a non-boost scenario.
> 
> It hides bug introduced into the kernel by the commit:
> "drm/i915: Define a separate variable and control for RPS waitboost frequency"
> 
> for GuC submission path, as the check below always holds true as we have
> waiters all the time:
>      if (client_boost || any_waiters) max = hw_max;
> 
> What was the point of this change?
> Were you aware of the fail in the guc_submission scenario?
> 
> -- 
> Cheers,
> Arek

Hi Arek. Yes, this was prompted by a regression of this subtest in Yocto
which uses GuC submission. I root caused it to this same i915 commit
from Chris but incorrectly thought that the new "policy" was that sysfs
max freq could be ignored in pretty much any situation. I understand now
that it should be ignored in only boost and real user wait situations
(not those triggered by GuC). So I do agree with this revert.

Is there an i915 fix coming soon? Chris?

Jeff
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