Imre Deak <imre.deak@xxxxxxxxx> writes: > 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: Oh yes, extra paranoia in here is warranted. I will add that. > Reviewed-by: Imre Deak <imre.deak@xxxxxxxxx> Thanks, -Mika > >> + } 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
