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authorVille Syrjälä <ville.syrjala@linux.intel.com>2015-08-26 22:55:07 +0300
committerJani Nikula <jani.nikula@intel.com>2015-09-02 16:13:43 +0300
commitf36203be608a38a5b5523a7aa52cc72f757b9679 (patch)
treea0cc8fdf761f93bcdb61d15ae4d2928457019510
parent4efa83c8c786ab7ec7982e3dd348cb7e7ecbeb04 (diff)
drm/dp: Add dp_aux_i2c_speed_khz module param to set the assume i2c bus speedtopic/drm-fixes-2015-09-09
To help with debugging i2c-over-aux issues, add a module parameter than can be used to tweak the assumed i2c bus speed, and thus the maximum number of retries we will do for each aux message. 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>
-rw-r--r--drivers/gpu/drm/drm_dp_helper.c13
1 files changed, 10 insertions, 3 deletions
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 214a4c649d56..291734e87fca 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -500,6 +500,15 @@ static int drm_dp_i2c_retry_count(const struct drm_dp_aux_msg *msg,
}
/*
+ * FIXME currently assumes 10 kHz as some real world devices seem
+ * to require it. We should query/set the speed via DPCD if supported.
+ */
+static int dp_aux_i2c_speed_khz __read_mostly = 10;
+module_param_unsafe(dp_aux_i2c_speed_khz, int, 0644);
+MODULE_PARM_DESC(dp_aux_i2c_speed_khz,
+ "Assumed speed of the i2c bus in kHz, (1-400, default 10)");
+
+/*
* Transfer a single I2C-over-AUX message and handle various error conditions,
* retrying the transaction as appropriate. It is assumed that the
* aux->transfer function does not modify anything in the msg other than the
@@ -517,10 +526,8 @@ static int drm_dp_i2c_do_msg(struct drm_dp_aux *aux, struct drm_dp_aux_msg *msg)
* before giving up the AUX transaction.
*
* We also try to account for the i2c bus speed.
- * FIXME currently assumes 10 kHz as some real world devices seem
- * to require it. We should query/set the speed via DPCD if supported.
*/
- int max_retries = max(7, drm_dp_i2c_retry_count(msg, 10));
+ int max_retries = max(7, drm_dp_i2c_retry_count(msg, dp_aux_i2c_speed_khz));
for (retry = 0, defer_i2c = 0; retry < (max_retries + defer_i2c); retry++) {
mutex_lock(&aux->hw_mutex);

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