[Intel-gfx] [PATCH] drm/i915: Perform link quality check unconditionally during long pulse
Manasi Navare
manasi.d.navare at intel.com
Thu Feb 16 17:07:53 UTC 2017
On Thu, Feb 16, 2017 at 05:30:07PM +0200, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
>
> Apparently some DP sinks are a little nuts and cause HPD to drop
> intermittently during modesets. This happens eg. on an ASUS PB287Q.
> In oder to recover from this we can't really use the previous
> connector status to determine if the link needs retraining, so let's
> just ignore that piece of information and do the retrain
> unconditionally. We do of course still check whether the link is
> supposed to be running or not.
>
> Cc: stable at vger.kernel.org
> Cc: Palmer Dabbelt <palmer at dabbelt.com>
> Reported-by: Palmer Dabbelt <palmer at dabbelt.com>
> References: https://lists.freedesktop.org/archives/intel-gfx/2017-February/119779.html
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
> drivers/gpu/drm/i915/intel_dp.c | 15 +++++++++++----
> 1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index 024798a9c016..37a746f7fbc3 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4648,11 +4648,18 @@ intel_dp_long_pulse(struct intel_connector *intel_connector)
> */
> status = connector_status_disconnected;
> goto out;
> - } else if (connector->status == connector_status_connected) {
> + } else {
> /*
> - * If display was connected already and is still connected
> - * check links status, there has been known issues of
> - * link loss triggerring long pulse!!!!
> + * If display is now connected check links status,
> + * there has been known issues of link loss triggerring
> + * long pulse.
> + *
> + * Some sinks (eg. ASUS PB287Q) seem to perform some
> + * weird HPD ping pong during modesets. So we can apparely
> + * end up with HPD going low during a modeset, and then
> + * going back up soon after. And once that happens we must
> + * retrain the link to get a picture. That's in case no
> + * userspace component reacted to intermittent HPD dip.
> */
> drm_modeset_lock(&dev->mode_config.connection_mutex, NULL);
> intel_dp_check_link_status(intel_dp);
> --
So here we basically just ignore the connector status and retrain irrespectively.
But that means even if we have newer values now for max link rate/lane count from
DPCD, during this retrain we are just using the stale value of intel_dp->link_rate
and intel_dp->lane_count. I think intel_dp->link_rate and lane count values
should be set to 0 on HPD pulse, they would be set only during a modeset.
Regards
Manasi
> 2.10.2
>
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