[Intel-gfx] [PATCHv5] drm/i915/dp: change aux_ctl reg read to polling read

[Arun R Murthy <arun.r.murthy@intel.com>]

The busy timeout logic checks for the AUX BUSY, then waits for the
timeout period and then after timeout reads the register for BUSY or
Success.
Instead replace interrupt with polling so as to read the AUX CTL
register often before the timeout period. Looks like there might be some
issue with interrupt-on-read. Hence changing the logic to polling read.

v2: replace interrupt with polling read
v3: use usleep_rang instead of msleep, updated commit msg
v4: use intel_wait_for_regiter internal function
v5: use __intel_de_wait_for_register with 500us slow and 10ms fast timeout

Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 35 ++++++---------------
 1 file changed, 9 insertions(+), 26 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c b/drivers/gpu/drm/i915/display/intel_dp_aux.c
index 91c93c93e5fc..772da38b451f 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -34,31 +34,6 @@ static void intel_dp_aux_unpack(u32 src, u8 *dst, int dst_bytes)
 		dst[i] = src >> ((3 - i) * 8);
 }
 
-static u32
-intel_dp_aux_wait_done(struct intel_dp *intel_dp)
-{
-	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;
-	bool done;
-
-#define C (((status = intel_de_read_notrace(i915, ch_ctl)) & DP_AUX_CH_CTL_SEND_BUSY) == 0)
-	done = wait_event_timeout(i915->display.gmbus.wait_queue, C,
-				  msecs_to_jiffies_timeout(timeout_ms));
-
-	/* just trace the final value */
-	trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
-
-	if (!done)
-		drm_err(&i915->drm,
-			"%s: did not complete or timeout within %ums (status 0x%08x)\n",
-			intel_dp->aux.name, timeout_ms, status);
-#undef C
-
-	return status;
-}
-
 static u32 g4x_get_aux_clock_divider(struct intel_dp *intel_dp, int index)
 {
 	struct drm_i915_private *dev_priv = dp_to_i915(intel_dp);
@@ -264,6 +239,7 @@ intel_dp_aux_xfer(struct intel_dp *intel_dp,
 	}
 
 	while ((aux_clock_divider = intel_dp->get_aux_clock_divider(intel_dp, clock++))) {
+		u32 timeout_ms = 10;
 		u32 send_ctl = intel_dp->get_aux_send_ctl(intel_dp,
 							  send_bytes,
 							  aux_clock_divider);
@@ -281,7 +257,14 @@ 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);
+			__intel_de_wait_for_register(i915, ch_ctl,
+						     DP_AUX_CH_CTL_SEND_BUSY, 0,
+						     500, timeout_ms, &status);
+
+			if ((status & DP_AUX_CH_CTL_SEND_BUSY) != 0)
+				drm_err(&i915->drm,
+					"%s: did not complete or timeout within %ums (status 0x%08x)\n",
+					intel_dp->aux.name, timeout_ms, status);
 
 			/* Clear done status and any errors */
 			intel_de_write(i915, ch_ctl,
-- 
2.25.1