[PATCH] drm/dp: Do not busy-loop during link training

[Thierry Reding]

From: Thierry Reding <treding at nvidia.com>

Use microsecond sleeps for the clock recovery and channel equalization
delays during link training. The duration of these delays can be from
100 us up to 16 ms. It is rude to busy-loop for that amount of time.

While at it, also convert to standard coding style by putting the
opening braces in a function definition on a new line.

Signed-off-by: Thierry Reding <treding at nvidia.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 73a3e0544f36..2dcc4efcd34c 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -125,19 +125,29 @@ u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZ
 }
 EXPORT_SYMBOL(drm_dp_get_adjust_request_post_cursor);
 
-void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
-	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
-		udelay(100);
+void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	unsigned int min;
+
+	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] != 0)
+		min = dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4000;
 	else
-		mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
+		min = 100;
+
+	usleep_range(min, min * 2);
 }
 EXPORT_SYMBOL(drm_dp_link_train_clock_recovery_delay);
 
-void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
-	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
-		udelay(400);
+void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	unsigned int min;
+
+	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] != 0)
+		min = dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4000;
 	else
-		mdelay(dpcd[DP_TRAINING_AUX_RD_INTERVAL] * 4);
+		min = 400;
+
+	usleep_range(min, min * 2);
 }
 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
 
-- 
2.5.0