On Fri, Sep 08, 2017 at 12:37:12PM +0300, Marta Lofstedt wrote: > During IGT testing it has been shown that the specification > defined polling time of 1 us for FCLK_DONE, is sometimes not > enough. This is most probably 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. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102243 > Signed-off-by: Marta Lofstedt <marta.lofstedt@xxxxxxxxx> I think it'd be good to add a summary of the alternate approaches you've tested (preempt_disable, pm_qos, ...), just for the record to indicate that there's quite a story hiding behind this patch. With that fixed, plus ofc assuming full igt doesn't spot any issues: Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx> Neat piece of hw r/eing here :-) -Daniel > --- > drivers/gpu/drm/i915/intel_cdclk.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c > index d32911816fc2..f89232e0f6fa 100644 > --- a/drivers/gpu/drm/i915/intel_cdclk.c > +++ b/drivers/gpu/drm/i915/intel_cdclk.c > @@ -669,8 +669,11 @@ 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); > -- > 2.11.0 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
