Re: [Intel-gfx] [PATCH 1/1] drm/i915: re-disable RC6p on Sandy Bridge

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Dec 21, 2022 at 09:09:17AM -0500, Rodrigo Vivi wrote:
> On Tue, Dec 20, 2022 at 12:32:05PM +0200, Ville Syrjälä wrote:
> > On Mon, Dec 19, 2022 at 06:29:27PM +0100, Sasa Dragic wrote:
> > > RC6p on Sandy Bridge got re-enabled over time, causing visual glitches
> > > and GPU hangs.
> > > 
> > > Disabled originally in commit 1c8ecf80fdee ("drm/i915: do not enable
> > > RC6p on Sandy Bridge").
> > 
> > re cover letter:
> > > It was originally disabled in commit 1c8ecf80fdee ("drm/i915: do not
> > > enable RC6p on Sandy Bridge"), and subsequently re-enabled by
> > > 13c5a577b342 ("drm/i915/gt: Select the deepest available parking mode
> > > for rc6"), which seems to focus only on Ivy Bridge.
> > 
> > That only kicks in while parked (ie. fully idle from
> > software POV). I think the real bad commit is
> > fb6db0f5bf1d ("drm/i915: Remove unsafe i915.enable_rc6")
> > which seems to affects which rc6 level is selected while
> > unparked.
> > 
> > We should mention both of those commits here:
> > Fixes: fb6db0f5bf1d ("drm/i915: Remove unsafe i915.enable_rc6")
> > Fixes: 13c5a577b342 ("drm/i915/gt: Select the deepest available parking mode for rc6")
> > 
> > Also we want
> > Cc: stable@vger.kernel.org
> > 
> > We can add those while pushing, so no need to resend for that.
> 
> agreed.
> 
> Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Pushed to drm-intel-gt-next. Thanks for the patch and review.

> 
> > 
> > > 
> > > Signed-off-by: Sasa Dragic <sasa.dragic@gmail.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_pci.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.c
> > > index 668e9da52584..69377564028a 100644
> > > --- a/drivers/gpu/drm/i915/i915_pci.c
> > > +++ b/drivers/gpu/drm/i915/i915_pci.c
> > > @@ -423,7 +423,8 @@ static const struct intel_device_info ilk_m_info = {
> > >  	.has_coherent_ggtt = true, \
> > >  	.has_llc = 1, \
> > >  	.has_rc6 = 1, \
> > > -	.has_rc6p = 1, \
> > > +	/* snb does support rc6p, but enabling it causes various issues */ \
> > > +	.has_rc6p = 0, \
> > 
> > The one downside of doing it this way is that we also lose
> > the debugfs/sysfs files so we can't monitor rc6+/++
> > residency anymore to make sure they are not entered.
> > 
> > I think ideally we'd split this into two parts: which rc6
> > states the hw actually has vs. which rc6 states we actually
> > want to use. But at least for the time being I think this
> > simple should be sufficient, and should be easy to backport
> > to stable releases.
> > 
> > >  	.has_rps = true, \
> > >  	.dma_mask_size = 40, \
> > >  	.__runtime.ppgtt_type = INTEL_PPGTT_ALIASING, \
> > > -- 
> > > 2.37.2
> > 
> > -- 
> > Ville Syrjälä
> > Intel

-- 
Ville Syrjälä
Intel