mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-25 02:09:42 +00:00
drm/i915: Increase poll time for BDW FCLK_DONE
During IGT testing it has been shown that the specification defined polling time of 1 us for FCLK_DONE, is sometimes not enough. The issue is still reproducible while disabling C-states through the PM QoS framework and also while disabling preemtion. From this the most plausible explanation is that the issue is due to a firmware flaw. As a workaround, it is better to wait a little bit longer for the FCLK_DONE to come around, than to leave with an DRM_ERROR and having FCLK_DONE at a randome time after. While spinning a list of igt tests prone to reproduce the issue the FCLK_DONE poll failed at approximately 2% of the invocations of the bdw_set_cdclk function. The longest poll time during this testing was measured to ~7us. So, the suggested new poll time of 100us is on the safe side. v2: Added more documentation about investigations done. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102243 Signed-off-by: Marta Lofstedt <marta.lofstedt@intel.com> Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20170908132829.6312-1-marta.lofstedt@intel.com
This commit is contained in:
parent
d0d5e0d7b1
commit
3164888a40
1 changed files with 5 additions and 1 deletions
|
@ -669,8 +669,12 @@ static void bdw_set_cdclk(struct drm_i915_private *dev_priv,
|
|||
val |= LCPLL_CD_SOURCE_FCLK;
|
||||
I915_WRITE(LCPLL_CTL, val);
|
||||
|
||||
/*
|
||||
* According to the spec, it should be enough to poll for this 1 us.
|
||||
* However, extensive testing shows that this can take longer.
|
||||
*/
|
||||
if (wait_for_us(I915_READ(LCPLL_CTL) &
|
||||
LCPLL_CD_SOURCE_FCLK_DONE, 1))
|
||||
LCPLL_CD_SOURCE_FCLK_DONE, 100))
|
||||
DRM_ERROR("Switching to FCLK failed\n");
|
||||
|
||||
val = I915_READ(LCPLL_CTL);
|
||||
|
|
Loading…
Reference in a new issue