drm/i915/bxt, glk: Increase PCODE timeouts during CDCLK freq changing
authorImre Deak <imre.deak@intel.com>
Tue, 30 Jan 2018 14:29:38 +0000 (16:29 +0200)
committerImre Deak <imre.deak@intel.com>
Thu, 1 Feb 2018 19:13:12 +0000 (21:13 +0200)
commite76019a81921e87a4d9e7b3d86102bc708a6c227
tree4433ef69ad995871de15a24c1f420bb2841fa498
parent28647b52ec0e20f84eb1b5e13095134e2b371759
drm/i915/bxt, glk: Increase PCODE timeouts during CDCLK freq changing

Currently we see sporadic timeouts during CDCLK changing both on BXT and
GLK as reported by the Bugzilla: ticket. It's easy to reproduce this by
changing the frequency in a tight loop after blanking the display. The
upper bound for the completion time is 800us based on my tests, so
increase it from the current 500us to 2ms; with that I couldn't trigger
the problem either on BXT or GLK.

Note that timeouts happened during both the change notification and the
voltage level setting PCODE request. (For the latter one BSpec doesn't
require us to wait for completion before further HW programming.)

This issue is similar to
commit 2c7d0602c815 ("drm/i915/gen9: Fix PCODE polling during CDCLK
change notification")
but there the PCODE request does complete (as shown by the mbox
busy flag), only the reply we get from PCODE indicates a failure.
So there we keep resending the request until a success reply, here we
just have to increase the timeout for the one PCODE request we send.

v2:
- s/snb_pcode_request/sandybridge_pcode_write_timeout/ (Ville)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: <stable@vger.kernel.org> # v4.4+
Acked-by: Chris Wilson <chris@chris-wilson.co.uk> (v1)
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103326
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180130142939.17983-1-imre.deak@intel.com
drivers/gpu/drm/i915/i915_drv.h
drivers/gpu/drm/i915/intel_cdclk.c
drivers/gpu/drm/i915/intel_pm.c