drm/msm/dp: Restore aux retry tuning logic

In commit 9fc41843 ("drm/msm/dp: unplug interrupt missed after
irq_hpd handler") we dropped a reset of the aux phy during aux transfers
because resetting the phy during active communication caused us to miss
an hpd irq in some cases. Unfortunately, we also dropped the part of the
code that changes the aux phy tuning when an aux transfer fails due to a
timeout. That part of the code was calling into the phy driver to
reconfigure the aux TX swing controls, working around poor channel
quality. Let's restore this phy setting code so that aux channel
communication is more reliable.

Cc: Kuogee Hsieh <khsieh@codeaurora.org>
Fixes: 9fc41843 ("drm/msm/dp: unplug interrupt missed after irq_hpd handler")
Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/dp/dp_aux.c

@@ -32,6 +32,8 @@ struct dp_aux_private {
 	struct drm_dp_aux dp_aux;
 };
 
+#define MAX_AUX_RETRIES			5
+
 static const char *dp_aux_get_error(u32 aux_error)
 {
 	switch (aux_error) {
@@ -377,6 +379,11 @@ static ssize_t dp_aux_transfer(struct drm_dp_aux *dp_aux,
 	ret = dp_aux_cmd_fifo_tx(aux, msg);
 
 	if (ret < 0) {
+		if (aux->native) {
+			aux->retry_cnt++;
+			if (!(aux->retry_cnt % MAX_AUX_RETRIES))
+				dp_catalog_aux_update_cfg(aux->catalog);
+		}
 		usleep_range(400, 500); /* at least 400us to next try */
 		goto unlock_exit;
 	}