From f36203be608a38a5b5523a7aa52cc72f757b9679 Mon Sep 17 00:00:00 2001 From: Ville Syrjälä Date: Wed, 26 Aug 2015 22:55:07 +0300 Subject: drm/dp: Add dp_aux_i2c_speed_khz module param to set the assume i2c bus speed MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: moosotc@gmail.com Signed-off-by: Ville Syrjälä Reviewed-by: Simon Farnsworth Reviewed-by: Daniel Vetter Signed-off-by: Jani Nikula --- drivers/gpu/drm/drm_dp_helper.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) (limited to 'drivers/gpu/drm/drm_dp_helper.c') 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 @@ -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); -- cgit v1.2.3-59-g8ed1b