On to, 2016-02-18 at 17:21 +0200, Mika Kuoppala wrote: > It has been observed that sometimes disabling the dc6 fails > and dc6 state pops back up, brief moment after disabling. This > has to be dmc save/restore timing issue or other bug in the > way dc states are handled. > > Try to work around this issue as we don't have firmware fix > yet available. Verify that the value we wrote for the dmc sticks, > and also enforce it by rewriting it, if it didn't. > > Testcase: kms_flip/basic-flip-vs-dpms > References: https://bugs.freedesktop.org/show_bug.cgi?id=93768 > Cc: Patrik Jakobsson <patrik.jakobsson@xxxxxxxxxxxxxxx> > Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> > Cc: Imre Deak <imre.deak@xxxxxxxxx> > Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx> > --- > drivers/gpu/drm/i915/intel_runtime_pm.c | 40 > +++++++++++++++++++++++++++++++-- > 1 file changed, 38 insertions(+), 2 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c > b/drivers/gpu/drm/i915/intel_runtime_pm.c > index 8b9290fdb3b2..cb91540cfbad 100644 > --- a/drivers/gpu/drm/i915/intel_runtime_pm.c > +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c > @@ -470,6 +470,42 @@ static void > gen9_set_dc_state_debugmask_memory_up( > } > } > > +static void gen9_write_dc_state(struct drm_i915_private *dev_priv, > + u32 state) > +{ > + int rewrites = 0; > + int rereads = 0; > + u32 v; > + > + I915_WRITE(DC_STATE_EN, state); > + > + /* It has been observed that disabling the dc6 state > sometimes > + * doesn't stick and dmc keeps returning old value. Make > sure > + * the write really sticks enough times and also force > rewrite until > + * we are confident that state is exactly what we want. > + */ > + do { > + v = I915_READ(DC_STATE_EN); > + > + if (v != state) { > + I915_WRITE(DC_STATE_EN, state); > + rewrites++; Could be rereads = 0; for extra paranoia. Either way: Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx> > + } else if (rereads++ > 5) { > + break; > + } > + > + } while (rewrites < 100); > + > + if (v != state) > + DRM_ERROR("Writing dc state to 0x%x failed, now > 0x%x\n", > + state, v); > + > + /* Most of the times we need one retry, avoid spam */ > + if (rewrites > 1) > + DRM_DEBUG_KMS("Rewrote dc state to 0x%x %d times\n", > + state, rewrites); > +} > + > static void gen9_set_dc_state(struct drm_i915_private *dev_priv, > uint32_t state) > { > uint32_t val; > @@ -502,8 +538,8 @@ static void gen9_set_dc_state(struct > drm_i915_private *dev_priv, uint32_t state) > > val &= ~mask; > val |= state; > - I915_WRITE(DC_STATE_EN, val); > - POSTING_READ(DC_STATE_EN); > + > + gen9_write_dc_state(dev_priv, val); > > dev_priv->csr.dc_state = val & mask; > } _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
