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

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>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20191021143437.1477719-7-thierry.reding@gmail.com
This commit is contained in:
Thierry Reding 2019-10-21 16:34:30 +02:00
parent 7624629d06
commit fc6b42045e
1 changed files with 18 additions and 12 deletions
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30
drivers/gpu/drm/drm_dp_helper.c
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@ -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);