On Fri, Nov 09, 2018 at 12:20:10PM -0800, José Roberto de Souza wrote:
> Some eDP panels do not set a valid sink count value and even for the
> ones that sets is should always be one for eDP, that is why it is not
> cached in intel_edp_init_dpcd().
>
> But intel_dp_short_pulse() compares the old count with the read one
> if there is a mistmatch a full port detection will be executed, what
> was happening in the first short pulse interruption of eDP panels
> that sets sink count.
>
> Instead of just skip the compasison for eDP panels, lets not read
> the sink count at all for eDP.
>
> v2: the previous version of this patch was caching the sink count
> in intel_edp_init_dpcd() but I was pointed out by Ville a patch that
> handled a case of a eDP panel that do not set sink count
>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> Signed-off-by: José Roberto de Souza <jose.souza@xxxxxxxxx>
Yeah, I guess we concluded that never reading it is totally fine.
Reviewed-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 44 +++++++++++++++++++--------------
> 1 file changed, 26 insertions(+), 18 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 2b090609bee2..577c166f6483 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -3936,8 +3936,6 @@ intel_edp_init_dpcd(struct intel_dp *intel_dp)
> static bool
> intel_dp_get_dpcd(struct intel_dp *intel_dp)
> {
> - u8 sink_count;
> -
> if (!intel_dp_read_dpcd(intel_dp))
> return false;
>
> @@ -3947,25 +3945,35 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
> intel_dp_set_common_rates(intel_dp);
> }
>
> - if (drm_dp_dpcd_readb(&intel_dp->aux, DP_SINK_COUNT, &sink_count) <= 0)
> - return false;
> -
> /*
> - * Sink count can change between short pulse hpd hence
> - * a member variable in intel_dp will track any changes
> - * between short pulse interrupts.
> + * Some eDP panels do not set a valid value for sink count, that is why
> + * it don't care about read it here and in intel_edp_init_dpcd().
> */
> - intel_dp->sink_count = DP_GET_SINK_COUNT(sink_count);
> + if (!intel_dp_is_edp(intel_dp)) {
> + u8 count;
> + ssize_t r;
>
> - /*
> - * SINK_COUNT == 0 and DOWNSTREAM_PORT_PRESENT == 1 implies that
> - * a dongle is present but no display. Unless we require to know
> - * if a dongle is present or not, we don't need to update
> - * downstream port information. So, an early return here saves
> - * time from performing other operations which are not required.
> - */
> - if (!intel_dp_is_edp(intel_dp) && !intel_dp->sink_count)
> - return false;
> + r = drm_dp_dpcd_readb(&intel_dp->aux, DP_SINK_COUNT, &count);
> + if (r < 1)
> + return false;
> +
> + /*
> + * Sink count can change between short pulse hpd hence
> + * a member variable in intel_dp will track any changes
> + * between short pulse interrupts.
> + */
> + intel_dp->sink_count = DP_GET_SINK_COUNT(count);
> +
> + /*
> + * SINK_COUNT == 0 and DOWNSTREAM_PORT_PRESENT == 1 implies that
> + * a dongle is present but no display. Unless we require to know
> + * if a dongle is present or not, we don't need to update
> + * downstream port information. So, an early return here saves
> + * time from performing other operations which are not required.
> + */
> + if (!intel_dp->sink_count)
> + return false;
> + }
>
> if (!drm_dp_is_branch(intel_dp->dpcd))
> return true; /* native DP sink */
> --
> 2.19.1
--
Ville Syrjälä
Intel
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