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From: Thierry Reding <thierry.reding@gmail.com>
To: dri-devel@lists.freedesktop.org
Subject: [PATCH v3 06/13] drm/dp: Do not busy-loop during link training
Date: Mon, 21 Oct 2019 16:34:30 +0200	[thread overview]
Message-ID: <20191021143437.1477719-7-thierry.reding@gmail.com> (raw)
In-Reply-To: <20191021143437.1477719-1-thierry.reding@gmail.com>

From: Thierry Reding <treding@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. Also switch to
using an unsigned int for the AUX read interval to match the data type
of the parameters to usleep_range().

v2: use correct multiplier for training delays (Philipp Zabel)
v3: clarify data type change in commit message

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
 drivers/gpu/drm/drm_dp_helper.c | 30 ++++++++++++++++++------------
 1 file changed, 18 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 8f2d7c4850ca..ac802b04f120 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -120,33 +120,39 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI
 }
 EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
 
-void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
-	int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
-			  DP_TRAINING_AUX_RD_MASK;
+void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	unsigned long rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
+					 DP_TRAINING_AUX_RD_MASK;
 
 	if (rd_interval > 4)
-		DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n",
+		DRM_DEBUG_KMS("AUX interval %lu, out of range (max 4)\n",
 			      rd_interval);
 
 	if (rd_interval == 0 || dpcd[DP_DPCD_REV] >= DP_DPCD_REV_14)
-		udelay(100);
+		rd_interval = 100;
 	else
-		mdelay(rd_interval * 4);
+		rd_interval *= 4 * USEC_PER_MSEC;
+
+	usleep_range(rd_interval, rd_interval * 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]) {
-	int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
-			  DP_TRAINING_AUX_RD_MASK;
+void drm_dp_link_train_channel_eq_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
+{
+	unsigned long rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] &
+					 DP_TRAINING_AUX_RD_MASK;
 
 	if (rd_interval > 4)
-		DRM_DEBUG_KMS("AUX interval %d, out of range (max 4)\n",
+		DRM_DEBUG_KMS("AUX interval %lu, out of range (max 4)\n",
 			      rd_interval);
 
 	if (rd_interval == 0)
-		udelay(400);
+		rd_interval = 400;
 	else
-		mdelay(rd_interval * 4);
+		rd_interval *= 4 * USEC_PER_MSEC;
+
+	usleep_range(rd_interval, rd_interval * 2);
 }
 EXPORT_SYMBOL(drm_dp_link_train_channel_eq_delay);
 
-- 
2.23.0

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  parent reply	other threads:[~2019-10-21 14:34 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-21 14:34 [PATCH v3 00/13] drm/dp: Move drm_dp_link helpers to Tegra DRM Thierry Reding
2019-10-21 14:34 ` [PATCH v3 01/13] drm/dp: Sort includes alphabetically Thierry Reding
2019-10-21 14:34 ` [PATCH v3 02/13] drm/dp: Remove a gratuituous blank line Thierry Reding
2019-10-21 14:34 ` [PATCH v3 03/13] drm/dp: Add drm_dp_fast_training_cap() helper Thierry Reding
2019-10-21 14:34 ` [PATCH v3 04/13] drm/dp: Add drm_dp_channel_coding_supported() helper Thierry Reding
2019-10-21 14:34 ` [PATCH v3 05/13] drm/dp: Add drm_dp_alternate_scrambler_reset_cap() helper Thierry Reding
2019-10-21 14:34 ` Thierry Reding [this message]
2019-10-22 14:04   ` [PATCH v3 06/13] drm/dp: Do not busy-loop during link training Daniel Vetter
2019-10-21 14:34 ` [PATCH v3 07/13] drm/dp: Add helper to get post-cursor adjustments Thierry Reding
2019-10-21 14:34 ` [PATCH v3 08/13] drm/bridge: analogix-anx78xx: Avoid drm_dp_link helpers Thierry Reding
2019-10-22 13:29   ` Daniel Vetter
2019-10-22 14:52     ` [PATCH v4] " Thierry Reding
2019-10-23  9:13       ` Daniel Vetter
2019-10-21 14:34 ` [PATCH v3 09/13] drm/bridge: tc358767: " Thierry Reding
2019-10-22 13:38   ` Daniel Vetter
2019-10-21 14:34 ` [PATCH v3 10/13] drm/bridge: tc358767: Use DP nomenclature Thierry Reding
2019-10-21 14:34 ` [PATCH v3 11/13] drm/msm: edp: Avoid drm_dp_link helpers Thierry Reding
2019-10-22 13:53   ` Daniel Vetter
2019-10-21 14:34 ` [PATCH v3 12/13] drm/rockchip: " Thierry Reding
2019-10-22 14:01   ` Daniel Vetter
2019-10-21 14:34 ` [PATCH v3 13/13] drm/tegra: Move drm_dp_link helpers to Tegra DRM Thierry Reding
2019-10-22 14:03   ` Daniel Vetter

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