[Intel-gfx] [PATCH] drm/i915/dp: Remove aux xfer timeout debug message

[Chris Wilson]

Quoting Souza, Jose (2021-01-04 14:50:59)
> On Thu, 2020-12-31 at 09:17 +0000, Chris Wilson wrote:
> > Quoting Almahallawy, Khaled (2020-12-31 01:24:34)
> > > On Wed, 2020-12-30 at 16:02 -0800, Matt Roper wrote:
> > > > On Wed, Dec 30, 2020 at 10:37:42AM +0000, Chris Wilson wrote:
> > > > > The timeouts are frequent and expected. We will complain if we
> > > > > retry so
> > > > > often as to lose patience and give up, so the cacophony from
> > > > > individual
> > > > > complaints is redundant.
> > > > > 
> > > > > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > > > 
> > > > Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
> > > > 
> > > > > ---
> > > > >  drivers/gpu/drm/i915/display/intel_dp.c | 2 --
> > > > >  1 file changed, 2 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > b/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > index 8ae769b18879..704e4cebf7f3 100644
> > > > > --- a/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > +++ b/drivers/gpu/drm/i915/display/intel_dp.c
> > > > > @@ -1613,8 +1613,6 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
> > > > >     /* Timeouts occur when the device isn't connected, so they're
> > > > >      * "normal" -- don't fill the kernel log with these */
> > > > >     if (status & DP_AUX_CH_CTL_TIME_OUT_ERROR) {
> > > > > -           drm_dbg_kms(&i915->drm, "%s: timeout (status
> > > > > 0x%08x)\n",
> > > > > -                       intel_dp->aux.name, status);
> > > 
> > > AUX timeout logs are very important for TGL TCSS Display debugging. We
> > > actually can get AUX timeout when the display is connected for the
> > > following reasons:
> > > * If AUX orientation is not configured correctly in BIOS
> > > * If USB3 dock is downgraded to USB2 and SBU/AUX lines are disabled
> > > * When LTTPR/Retimer started to act funny and not configured correctly
> > > by EC
> > > * When we have a bug in the PMC mux configuration because of bug in the
> > > following files: drivers/usb/typec/mux/intel_pmc_mux.c and
> > > drivers/platform/x86/intel_scu_ipc.c
> > > * When user space is not cleanly disconnected all MST connectors for
> > > disconnected MST hub with 2+ display. We will be left with enabled
> > > pipes although the cable is disconnected and next connect of type-c
> > > display will give aux timeout: 
> > >   ** User space fix in Chrome: 
> > > https://chromium-review.googlesource.com/c/chromium/src/+/2512550/ 
> > >   ** WA in driver: https://patchwork.freedesktop.org/patch/395901/ 
> > > 
> > > These logs are especially important for Chrome based platforms with
> > > type-C. Seeing these logs we can know who is screwing up (TCSS driver,
> > > CB, or EC).
> > 
> > Then capture the information you require to analyse your failures.
> > Flooding the debug log makes debugging everything else much, much harder.
> > -Chris
> 
> I agree with Khaled this message is helpful to debug why display is not coming up.

Isn't that the case where it falls through to the later timeout warning?

If there's some information in there to explain a display failure, can
it be extracted automatically? Or to turn the table around, if it is so
useful to debug failures, why do we still see it in CI?
-Chris