Re: [Intel-gfx] [PATCH 4/4] DO_NOT_MERGE: drm/i915/display: Enable PSR2 selective fetch by default

["Souza, Jose" <jose.souza@intel.com>]

On Thu, 2021-08-05 at 21:26 +0300, Gwan-gyeong Mun wrote:
> 
> On 8/3/21 8:18 PM, Souza, Jose wrote:
> > On Tue, 2021-08-03 at 14:17 +0300, Gwan-gyeong Mun wrote:
> > > 
> > > On 7/31/21 3:10 AM, José Roberto de Souza wrote:
> > > > Only to execute tests with PSR2 selective fetch enabled and check what
> > > > is broken.
> > > > 
> > > > IGT tests know to fail with this:
> > > > - kms_cursor_legacy: all tests that checks if evasion happend, I have
> > > > fix for it making cursor_slowpath() returns true for display 12+.
> > > > 
> > > > - kms_psr2_su: The pageflip test, it needs to have the damage clip set
> > > > otherwise it will update the whole screen and the selective blocks
> > > > will not match with expected.
> > > > 
> > > kms_psr2_su is a test case for intel PSR2 HW tracking and kms_psr2_sf is
> > > used as a test for intel PSR2 manual tracking. Is it necessary to modify
> > > kms_psr2_su for testing PSR2 manual tracking?
> > 
> > kms_psr2_su is to test that PSR2 is sending selective updates, just adding a couple of lines we can make it work with selective fetch.
> > 
> > > > - kms_psr: psr2_*_(mmap_gtt, mmap_cpu, blt and render), all those
> > > > tests should be dropped or skipped for display 12+.
> > > > 
> > > Could you explain in more detail why we need to skip on display 12+?
> > 
> > This are stuff that would end up calling intel_psr_invalidate/flush().
> > 
> 
> Thanks for the explanation.
> And there is an issue confirmed in local tests, so I leave additional 
> comments.
> > > 
> > > > Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
> > > > ---
> > > >    drivers/gpu/drm/i915/display/intel_psr.c | 9 ---------
> > > >    drivers/gpu/drm/i915/i915_params.h       | 2 +-
> > > >    2 files changed, 1 insertion(+), 10 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
> > > > index 894a2d35668a2..e128f0c2aeecc 100644
> > > > --- a/drivers/gpu/drm/i915/display/intel_psr.c
> > > > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
> > > > @@ -877,15 +877,6 @@ static bool intel_psr2_config_valid(struct intel_dp *intel_dp,
> > > >    return false;
> > > >    }
> > > > 
> > > > -/*
> > > > - * We are missing the implementation of some workarounds to enabled PSR2
> > > > - * in Alderlake_P, until ready PSR2 should be kept disabled.
> > > > - */
> > > > -if (IS_ALDERLAKE_P(dev_priv)) {
> > > > -drm_dbg_kms(&dev_priv->drm, "PSR2 is missing the implementation of workarounds\n");
> > > > -return false;
> > > > -}
> > > > -
> > > >    if (!transcoder_has_psr2(dev_priv, crtc_state->cpu_transcoder)) {
> > > >    drm_dbg_kms(&dev_priv->drm,
> > > >        "PSR2 not supported in transcoder %s\n",
> > > > diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
> > > > index f27eceb82c0f5..8d725b64592d8 100644
> > > > --- a/drivers/gpu/drm/i915/i915_params.h
> > > > +++ b/drivers/gpu/drm/i915/i915_params.h
> > > > @@ -55,7 +55,7 @@ struct drm_printer;
> > > >    param(int, enable_fbc, -1, 0600) \
> > > >    param(int, enable_psr, -1, 0600) \
> > > >    param(bool, psr_safest_params, false, 0400) \
> > > > -param(bool, enable_psr2_sel_fetch, false, 0400) \
> > > > +param(bool, enable_psr2_sel_fetch, true, 0400) \
> If we do not modify this part and do not enable it by default at boot 
> time as shown in the original code below,
> param(bool, enable_psr2_sel_fetch, false, 0400) \
> 
> when we execute the kms_psr2_sf test case of igt, the FIFO underrun as 
> below still occurs.
> 
> i915 0000:00:02.0: [drm] *ERROR* CPU pipe A FIFO underrun: port,transcoder,
> 
> When PSR2 panel is used, PSR1 is enabled by default when 
> enable_psr2_sel_fetch is not enabled by default.
> And when kms_psr2_sf is executed, the mode is changed to PSR2, and when 
> kms_psr2_sf is terminated, PSR2 is deactivated and PSR1 is re-enabled. 
> At this point. I suspect there is a problem.

Was able to reproduce this even with enable_psr2_sel_fetch set to true.
Added some debug messages to intel_psr_exit() and intel_psr_activate() and those functions are not called and the underrun still happens.

Could be a regression recently introduced because I was not seeing this underrun a few weeks ago.
Anyways this underrun happens with and without(just doing the changes to allow PSR2 in alderlake-P in intel_psr2_config_valid()) this patches.

> 
> > > >    param(int, disable_power_well, -1, 0400) \
> > > >    param(int, enable_ips, 1, 0600) \
> > > >    param(int, invert_brightness, 0, 0600) \
> > > > 
> >