[PATCH] drm/i915/dp: Use poll read for detecting AUX pending transaction

[Arun R Murthy]

While performing a new AUX transfer, check was done to sense any previous
pending transaction in progress with a delayed read in a loop. Replace
this with a polling read function(hybrid scheme with fast register waits).

Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 32 +++++++--------------
 1 file changed, 10 insertions(+), 22 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 5a176bfb10a2..226c730c3219 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -35,11 +35,10 @@ static void intel_dp_aux_unpack(u32 src, u8 *dst, int dst_bytes)
 }
 
 static u32
-intel_dp_aux_wait_done(struct intel_dp *intel_dp)
+intel_dp_aux_wait_done(struct intel_dp *intel_dp, const unsigned int timeout_ms)
 {
 	struct drm_i915_private *i915 = dp_to_i915(intel_dp);
 	i915_reg_t ch_ctl = intel_dp->aux_ch_ctl_reg(intel_dp);
-	const unsigned int timeout_ms = 10;
 	u32 status;
 	int ret;
 
@@ -199,6 +198,8 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	int try, clock = 0;
 	u32 status;
 	bool vdd;
+	const unsigned int write_ack_timeout_ms = 10;
+	const unsigned int transaction_timeout_ms = 3;
 
 	ch_ctl = intel_dp->aux_ch_ctl_reg(intel_dp);
 	for (i = 0; i < ARRAY_SIZE(ch_data); i++)
@@ -230,25 +231,11 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	intel_pps_check_power_unlocked(intel_dp);
 
 	/* Try to wait for any previous AUX channel activity */
-	for (try = 0; try < 3; try++) {
-		status = intel_de_read_notrace(i915, ch_ctl);
-		if ((status & DP_AUX_CH_CTL_SEND_BUSY) == 0)
-			break;
-		msleep(1);
-	}
-	/* just trace the final value */
-	trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
-
-	if (try == 3) {
-		const u32 status = intel_de_read(i915, ch_ctl);
-
-		if (status != intel_dp->aux_busy_last_status) {
-			drm_WARN(&i915->drm, 1,
-				 "%s: not started (status 0x%08x)\n",
-				 intel_dp->aux.name, status);
-			intel_dp->aux_busy_last_status = status;
-		}
-
+	status = intel_dp_aux_wait_done(intel_dp, transaction_timeout_ms);
+	if ((status & DP_AUX_CH_CTL_SEND_BUSY) != 0) {
+		drm_WARN(&i915->drm, 1,
+			 "%s: not started (status 0x%08x)\n",
+			 intel_dp->aux.name, status);
 		ret = -EBUSY;
 		goto out;
 	}
@@ -277,7 +264,8 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 			/* Send the command and wait for it to complete */
 			intel_de_write(i915, ch_ctl, send_ctl);
 
-			status = intel_dp_aux_wait_done(intel_dp);
+			status = intel_dp_aux_wait_done(intel_dp,
+							write_ack_timeout_ms);
 
 			/* Clear done status and any errors */
 			intel_de_write(i915, ch_ctl,
-- 
2.25.1