On Fri, 2018-05-11 at 12:51 -0700, Dhinakaran Pandiyan wrote:
> Noticed that we assume the best case of 0 latency when the DPCD read
> fails, reasonable pessimism is safer.
>
> eDP spec does say that if latency is greater than 8, the panel
> supplier needs to provide it. I didn't see anything specific in the
> VBT
> for this, so let's go with 8 frames as a fallback.
>
> Cc: Jose Roberto de Souza <jose.souza@xxxxxxxxx>
> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Reviewed-by: José Roberto de Souza <jose.souza@xxxxxxxxx>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> ---
> drivers/gpu/drm/i915/intel_psr.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_psr.c
> b/drivers/gpu/drm/i915/intel_psr.c
> index 381dbdbf30f4..b4a4f5d3a2bb 100644
> --- a/drivers/gpu/drm/i915/intel_psr.c
> +++ b/drivers/gpu/drm/i915/intel_psr.c
> @@ -223,13 +223,13 @@ static bool intel_dp_get_alpm_status(struct
> intel_dp *intel_dp)
>
> static u8 intel_dp_get_sink_sync_latency(struct intel_dp *intel_dp)
> {
> - u8 val = 0;
> + u8 val = 8; /* assume the worst if we can't read the value
> */
>
> if (drm_dp_dpcd_readb(&intel_dp->aux,
> DP_SYNCHRONIZATION_LATENCY_IN_SINK,
> &val) == 1)
> val &= DP_MAX_RESYNC_FRAME_COUNT_MASK;
> else
> - DRM_ERROR("Unable to get sink synchronization
> latency\n");
> + DRM_DEBUG_KMS("Unable to get sink synchronization
> latency, assuming 8 frames\n");
Maybe have this at least as a warning.
> return val;
> }
>
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