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Either the command might be wrong or sink in > an unknown/sleep state can cause this. So try waking the sink device. > Before reading the DPCD caps wake the sink for eDP and for DP after > reading the lttpr caps if present and before reading the dpcd caps wake > up the sink device. > > v2: Use poll_timeout_us (Jani N) > Add the reason, why this change is required (Ville) > > Closes: https://issues.redhat.com/browse/RHEL-120913 I wonder what should be the rule with non-public links like the above. For instance, we do not put VLK-xxx links exactly because those are non-public. Should/could we demand that RedHat opens a public ticket? Jani? > Signed-off-by: Arun R Murthy > --- > drivers/gpu/drm/i915/display/intel_dp.c | 38 +++++++++++++++++++ > drivers/gpu/drm/i915/display/intel_dp.h | 1 + > .../drm/i915/display/intel_dp_link_training.c | 3 ++ > 3 files changed, 42 insertions(+) > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.c b/drivers/gpu/drm/i915/display/intel_dp.c > index 025e906b63a9..fa0730f7b92a 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.c > +++ b/drivers/gpu/drm/i915/display/intel_dp.c > @@ -4705,6 +4705,42 @@ intel_edp_set_sink_rates(struct intel_dp *intel_dp) > intel_edp_set_data_override_rates(intel_dp); > } > > +/* Spec says to try for 3 times, its doubled to add the software overhead */ > +#define AUX_CH_WAKE_RETRY 6 > + > +void intel_dp_wake_sink(struct intel_dp *intel_dp) > +{ > + u8 value = 0; > + int ret = 0; > + > + intel_dp_dpcd_set_probe(intel_dp, false); Is there any particular reason to turn off/on the probing? I don't see any reason why the DP_SET_POWER polling would need that. In any case turning it off/on this way is not ok: reading the DPRX caps, which would call this function, could happen at any time after a sink gets connected, so turning probing back on at the end of this function would re-enable it incorrectly for sinks where it's been already established that the probing workaround is not needed and should stay disabled. > + > + /* > + * Wake the sink device > + * Spec DP2.1 section 2.3.1.2 if AUX CH is powered down by writing 0x02 > + * to DP_SET_POWER dpcd reg, 1ms time would be required to wake it up > + */ > + ret = poll_timeout_us(ret = drm_dp_dpcd_readb(&intel_dp->aux, DP_SET_POWER, &value), > + ret > 0, > + 1000, AUX_CH_WAKE_RETRY * 1000, true); > + > + /* > + * If sink is in D3 then it may not respond to the AUX tx so > + * wake it up to D3_AUX_ON state > + * If the above poll_timeout_us fails, try waking the sink. > + */ > + if (value == DP_SET_POWER_D3 || ret < 0) { > + /* After setting to D0 need a min of 1ms to wake(Spec DP2.1 sec 2.3.1.2) */ > + drm_dp_dpcd_writeb(&intel_dp->aux, DP_SET_POWER, > + DP_SET_POWER_D0); > + fsleep(1000); > + drm_dp_dpcd_writeb(&intel_dp->aux, DP_SET_POWER, > + DP_SET_POWER_D3_AUX_ON); > + } > + > + intel_dp_dpcd_set_probe(intel_dp, true); > +} > + > static bool > intel_edp_init_dpcd(struct intel_dp *intel_dp, struct intel_connector *connector) > { > @@ -4713,6 +4749,8 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp, struct intel_connector *connector > /* this function is meant to be called only once */ > drm_WARN_ON(display->drm, intel_dp->dpcd[DP_DPCD_REV] != 0); > > + intel_dp_wake_sink(intel_dp); > + > if (drm_dp_read_dpcd_caps(&intel_dp->aux, intel_dp->dpcd) != 0) > return false; > > diff --git a/drivers/gpu/drm/i915/display/intel_dp.h b/drivers/gpu/drm/i915/display/intel_dp.h > index b0bbd5981f57..3f16077c0cc7 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp.h > +++ b/drivers/gpu/drm/i915/display/intel_dp.h > @@ -232,6 +232,7 @@ bool intel_dp_dotclk_valid(struct intel_display *display, > bool intel_dp_joiner_candidate_valid(struct intel_connector *connector, > int hdisplay, > int num_joined_pipes); > +void intel_dp_wake_sink(struct intel_dp *intel_dp); > > #define for_each_joiner_candidate(__connector, __mode, __num_joined_pipes) \ > for ((__num_joined_pipes) = 1; (__num_joined_pipes) <= (I915_MAX_PIPES); (__num_joined_pipes)++) \ > diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_training.c b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > index 54c585c59b90..cbb712ea9f60 100644 > --- a/drivers/gpu/drm/i915/display/intel_dp_link_training.c > +++ b/drivers/gpu/drm/i915/display/intel_dp_link_training.c > @@ -270,6 +270,9 @@ int intel_dp_init_lttpr_and_dprx_caps(struct intel_dp *intel_dp) > lttpr_count = intel_dp_init_lttpr(intel_dp, dpcd); > } > > + /* After reading LTTPR wake up the sink before reading DPRX caps */ > + intel_dp_wake_sink(intel_dp); > + > /* > * The DPTX shall read the DPRX caps after LTTPR detection, so re-read > * it here. > -- > 2.25.1 >