drm/dp: Define AUX_RETRY_INTERVAL as 500 us

Currently we react to native and i2c defers by waiting either 400-500 us
or 500-600 us, depending on which code path we take. Consolidate them
all to one define AUX_RETRY_INTERVAL which defines the minimum interval.
Since we've been using two different intervals pick the longer of them
and define AUX_RETRY_INTERVAL as 500 us. For the maximum just use
AUX_RETRY_INTERVAL+100 us.

I want to have a define for this so that I can use it when calculating
the estimated duration of i2c-over-aux transfers. Without a define it
would be very easy to change the sleep duration and neglect to update
the i2c-over-aux estimates.

Cc: Simon Farnsworth <simon.farnsworth@onelan.com>
Cc: moosotc@gmail.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Simon Farnsworth <simon.farnsworth@onelan.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 80a02a412607f9c1b38e20b5494033b969c9e800..7069e54e5b43c6bc3e794b19547019846276571f 100644 (file)
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -159,6 +159,8 @@ int drm_dp_bw_code_to_link_rate(u8 link_bw)
 }
 EXPORT_SYMBOL(drm_dp_bw_code_to_link_rate);
 
+#define AUX_RETRY_INTERVAL 500 /* us */
+
 /**
  * DOC: dp helpers
  *
@@ -213,7 +215,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
                        return -EIO;
 
                case DP_AUX_NATIVE_REPLY_DEFER:
-                       usleep_range(400, 500);
+                       usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
                        break;
                }
        }
@@ -476,7 +478,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
                         * For now just defer for long enough to hopefully be
                         * safe for all use-cases.
                         */
-                       usleep_range(500, 600);
+                       usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
                        continue;
 
                default:
@@ -506,7 +508,7 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
                        aux->i2c_defer_count++;
                        if (defer_i2c < 7)
                                defer_i2c++;
-                       usleep_range(400, 500);
+                       usleep_range(AUX_RETRY_INTERVAL, AUX_RETRY_INTERVAL + 100);
                        continue;
 
                default: