From: Ville Syrjälä ville.syrjala@linux.intel.com
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 --- drivers/gpu/drm/drm_dp_helper.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 23b9fcc..ee5cd86 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -497,6 +497,15 @@ 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 @@ -514,10 +523,8 @@ 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);