Re: [PATCH] drm/i915/edp: Increase T12 panel delay to 900 ms to fix DP AUX CH timeouts

[Manasi Navare <manasi.d.navare@intel.com>]

On Wed, Aug 16, 2017 at 03:54:35PM -0700, Clint Taylor wrote:
> 
> 
> On 08/16/2017 02:19 PM, Rodrigo Vivi wrote:
> >It seems this quirk is randomly masking the real issue.
> It could be masking the real issue. The most likely cause of this issue is a
> slow power fall off to the panel when the PPS requests power-off. We would
> need physical access to the platform itself to confirm by measuring the
> power fall off with a scope. We could also instrument a Gen9 platform and
> confirm the panel power sequencer is working correctly. However that will
> not show why this particular tcon appears to no longer communicate after a
> reset.
> 
> -Clint
> 
>

Yes I had actually added debug prints to check the status of the HPD pin
before the link training and it is 0. That means that the eDP panel power
never actually turned back on. But if we give enough time for this panel
power cycling then it turns the panel power correctly and issue is gone.
So I think increasing this delay is the fix for the issue on this specific
panel.

Regards
Manasi
 
> 
> >
> >On Wed, Aug 16, 2017 at 12:35 PM, Manasi Navare
> ><manasi.d.navare@intel.com> wrote:
> >>Hi Daniel/Clint,
> >>
> >>Could you review this one, we need this patch to get pushed
> >>to drm-tip so that we can see if SKL 6700hq is stable with this patch.
> >>Thanks a lot in advanvce!
> >>
> >>Regards
> >>Manasi
> >>
> >>On Tue, Aug 15, 2017 at 11:59:51AM -0700, Manasi Navare wrote:
> >>>This patch fixes the DP AUX CH timeouts observed during CI runs causing
> >>>CI Failures on a specific PCI device. This issue was fixed previously
> >>>by adding a quirk but looks like we need to increase this delay even more
> >>>in order to get rid all the DP AUX CH timeouts.
> >>>
> >>>Fixes: c99a259b4b5192ba ("drm/i915/edp: Add a T12 panel delay quirk to fix
> >>>DP AUX CH timeouts")
> >>>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101144
> >>>Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> >>>Cc: Clinton Taylor <clinton.a.taylor@intel.com>
> >>>Cc: Daniel Vetter <daniel.vetter@intel.com>
> >>>Cc: Tomi Sarvela <tomi.p.sarvela@intel.com>
> >>>---
> >>>  drivers/gpu/drm/i915/intel_dp.c | 2 +-
> >>>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>>
> >>>diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> >>>index 5ba8366..c4d8afa 100644
> >>>--- a/drivers/gpu/drm/i915/intel_dp.c
> >>>+++ b/drivers/gpu/drm/i915/intel_dp.c
> >>>@@ -5246,7 +5246,7 @@ intel_dp_init_panel_power_sequencer(struct drm_device *dev,
> >>>        * seems sufficient to avoid this problem.
> >>>        */
> >>>       if (dev_priv->quirks & QUIRK_INCREASE_T12_DELAY) {
> >>>-             vbt.t11_t12 = max_t(u16, vbt.t11_t12, 800 * 10);
> >>>+             vbt.t11_t12 = max_t(u16, vbt.t11_t12, 900 * 10);
> >>>               DRM_DEBUG_KMS("Increasing T12 panel delay as per the quirk to %d\n",
> >>>                             vbt.t11_t12);
> >>>       }
> >>>--
> >>>2.1.4
> >>>
> >>_______________________________________________
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> >>Intel-gfx@lists.freedesktop.org
> >>https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> >
> >
> 
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