The number of AUX retries specified in the DP specs is 7. Currently, to make Dell 4k monitors happier, the number of retries are 32.
i915 also retries 5 times (intel_dp_aux_xfer) which means in the case of AUX timeout we actually retries 32 * 5 = 160 times.
So making the number of aux retires a variable to allow for fine tuning and optimization of aux timing.
Signed-off-by: Khaled Almahallawy <khaled.almahallawy@xxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 10 +++-------
include/drm/drm_dp_helper.h | 1 +
2 files changed, 4 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index eedbb48815b7..8fdf57b4a06c 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -249,13 +249,7 @@ static int drm_dp_dpcd_access(struct drm_dp_aux *aux, u8 request,
mutex_lock(&aux->hw_mutex);
- /*
- * The specification doesn't give any recommendation on how often to
- * retry native transactions. We used to retry 7 times like for
- * aux i2c transactions but real world devices this wasn't
- * sufficient, bump to 32 which makes Dell 4k monitors happier.
- */
- for (retry = 0; retry < 32; retry++) {
+ for (retry = 0; retry < aux->num_retries; retry++) {
if (ret != 0 && ret != -ETIMEDOUT) {
usleep_range(AUX_RETRY_INTERVAL,
AUX_RETRY_INTERVAL + 100);
@@ -1744,6 +1738,8 @@ void drm_dp_aux_init(struct drm_dp_aux *aux)
aux->ddc.retries = 3;
aux->ddc.lock_ops = &drm_dp_i2c_lock_ops;
+ /*Still making the Dell 4k monitors happier*/
+ aux->num_retries = 32;
}
EXPORT_SYMBOL(drm_dp_aux_init);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index edffd1dcca3e..16cbfc8f5e66 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1876,6 +1876,7 @@ struct drm_dp_aux {
struct mutex hw_mutex;
struct work_struct crc_work;
u8 crc_count;
+ int num_retries;
ssize_t (*transfer)(struct drm_dp_aux *aux,
struct drm_dp_aux_msg *msg);
/**
--
2.25.1
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