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

[Souza, Jose]

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.