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Commit f36203be authored by Ville Syrjälä's avatar Ville Syrjälä Committed by Jani Nikula
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drm/dp: Add dp_aux_i2c_speed_khz module param to set the assume i2c bus speed 



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: default avatarVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: default avatarSimon Farnsworth <simon.farnsworth@onelan.com>
Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
parent 4efa83c8

drivers/gpu/drm/drm_dp_helper.c

+10 −3
Original line number Diff line number Diff line
@@ -499,6 +499,15 @@ static int drm_dp_i2c_retry_count(const struct drm_dp_aux_msg *msg, 
	return DIV_ROUND_UP(i2c_time_us, aux_time_us + AUX_RETRY_INTERVAL);

}



/*

 * 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
@@ -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);