[Intel-gfx] [PATCHv6] 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
v6: check return value of __intel_de_wait_for_register

Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
---
 drivers/gpu/drm/i915/display/intel_dp_aux.c | 15 +++++----------
 1 file changed, 5 insertions(+), 10 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..dec88f41380e 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
@@ -40,21 +40,16 @@ 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));
+	u32 status, ret;
 
-	/* just trace the final value */
-	trace_i915_reg_rw(false, ch_ctl, status, sizeof(status), true);
+	ret = __intel_de_wait_for_register(i915, ch_ctl,
+				     DP_AUX_CH_CTL_SEND_BUSY, 0,
+				     500, timeout_ms, &status);
 
-	if (!done)
+	if (ret == -ETIMEDOUT)
 		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;
 }
-- 
2.25.1