The section 5.1.4 of the v1.2 DisplayPort standard says
> The Source device shall respond to Hot Plug event/Hot Re-plug event by
> first reading DPCD Link/Sink Device Status registers at DPCD 00200h
> through 00205h.... If the link is unstable or lost, the Source device
> then reads the DPCD Receiver Capabilities registers at DPCD 00000h
> through 0000Fh to determine the appropriate information needed to
> train the link. The Source device shall then initiate link training.
However, zynqmp_dp_hpd_work_func does not check the link status. This
may prevent the sink from detecting the source if, for example, the user
disconnects the cable and then reconnects it. I encountered this problem
when testing a mini DP connector (although I had no problem when using a
full-size connector with the existing driver).
Follow the spec by checking the link status after a HPD event and
retraining if necessary.
Fixes: d76271d22694 ("drm: xlnx: DRM/KMS driver for Xilinx ZynqMP DisplayPort
Subsystem")
Signed-off-by: Sean Anderson <[email protected]>
---
Changes in v2:
- needs_retain -> needs_retrain
- Actually retrain the loop (accidentally removed while rebasing)
drivers/gpu/drm/xlnx/zynqmp_dp.c | 38 ++++++++++++++++++++------------
1 file changed, 24 insertions(+), 14 deletions(-)
diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index caf2e0ce3644..1619aa61f7e1 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -1677,6 +1677,24 @@ static int zynqmp_dp_bridge_atomic_check(struct
drm_bridge *bridge,
return 0;
}
+static bool zynqmp_hpd_needs_retrain(struct zynqmp_dp *dp)
+{
+ u8 status[DP_LINK_STATUS_SIZE + 2];
+ int err;
+
+ err = drm_dp_dpcd_read(&dp->aux, DP_SINK_COUNT, status,
+ DP_LINK_STATUS_SIZE + 2);
+ if (err < 0) {
+ dev_dbg_ratelimited(dp->dev,
+ "could not read sink status: %d\n", err);
+ return false;
+ }
+
+ return status[4] & DP_LINK_STATUS_UPDATED ||
+ !drm_dp_clock_recovery_ok(&status[2], dp->mode.lane_cnt) ||
+ !drm_dp_channel_eq_ok(&status[2], dp->mode.lane_cnt);
+}
+
static enum drm_connector_status __zynqmp_dp_bridge_detect(struct zynqmp_dp
*dp)
{
struct zynqmp_dp_link_config *link_config = &dp->link_config;
@@ -1698,6 +1716,9 @@ static enum drm_connector_status
__zynqmp_dp_bridge_detect(struct zynqmp_dp *dp)
if (state & ZYNQMP_DP_INTERRUPT_SIGNAL_STATE_HPD) {
WRITE_ONCE(dp->status, connector_status_connected);
+ if (!zynqmp_hpd_needs_retrain(dp))
+ return connector_status_connected;
+
ret = drm_dp_dpcd_read(&dp->aux, 0x0, dp->dpcd,
sizeof(dp->dpcd));
if (ret < 0) {
@@ -1712,6 +1733,7 @@ static enum drm_connector_status
__zynqmp_dp_bridge_detect(struct zynqmp_dp *dp)
drm_dp_max_lane_count(dp->dpcd),
dp->num_lanes);
+ zynqmp_dp_train_loop(dp);
return connector_status_connected;
}
@@ -2335,25 +2357,13 @@ static void zynqmp_dp_hpd_irq_work_func(struct
work_struct *work)
{
struct zynqmp_dp *dp = container_of(work, struct zynqmp_dp,
hpd_irq_work);
- u8 status[DP_LINK_STATUS_SIZE + 2];
- int err;
guard(mutex)(&dp->lock);
if (dp->ignore_hpd)
return;
- err = drm_dp_dpcd_read(&dp->aux, DP_SINK_COUNT, status,
- DP_LINK_STATUS_SIZE + 2);
- if (err < 0) {
- dev_dbg_ratelimited(dp->dev,
- "could not read sink status: %d\n", err);
- } else {
- if (status[4] & DP_LINK_STATUS_UPDATED ||
- !drm_dp_clock_recovery_ok(&status[2], dp->mode.lane_cnt) ||
- !drm_dp_channel_eq_ok(&status[2], dp->mode.lane_cnt)) {
- zynqmp_dp_train_loop(dp);
- }
- }
+ if (zynqmp_hpd_needs_retrain(dp))
+ zynqmp_dp_train_loop(dp);
}
static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
--
2.35.1.1320.gc452695387.dirty
