From: Thierry Reding treding@nvidia.com
Store the AUX read interval from DPCD, so that it can be used to wait for the durations given in the specification during link training.
Signed-off-by: Thierry Reding treding@nvidia.com --- include/drm/drm_dp_helper.h | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+)
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 7a537ffc2fb1..6c12de6f7e46 100644 --- a/include/drm/drm_dp_helper.h +++ b/include/drm/drm_dp_helper.h @@ -25,8 +25,11 @@
#include <linux/delay.h> #include <linux/i2c.h> +#include <linux/time64.h> #include <linux/types.h>
+#include <drm/drm_print.h> + /* * Unless otherwise noted, all values are from the DP 1.1a spec. Note that * DP and DPCD versions are independent. Differences from 1.0 are not noted, @@ -1297,6 +1300,36 @@ drm_dp_alternate_scrambler_reset_cap(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) DP_ALTERNATE_SCRAMBLER_RESET_CAP; }
+/** + * drm_dp_read_aux_interval() - read the AUX read interval from the DPCD + * @dpcd: receiver capacity buffer + * + * Reads the AUX read interval (in microseconds) from the DPCD. Note that the + * TRAINING_AUX_RD_INTERVAL stores the value in units of 4 milliseconds. If no + * read interval is specified and for DPCD v1.4 and later, the read interval + * is always 100 microseconds. + * + * Returns: + * The read AUX interval in microseconds. + */ +static inline unsigned int +drm_dp_aux_rd_interval(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) +{ + unsigned int rd_interval = dpcd[DP_TRAINING_AUX_RD_INTERVAL] & + DP_TRAINING_AUX_RD_MASK; + + if (rd_interval > 4) + DRM_DEBUG_KMS("AUX interval %u, out of range (max: 4)\n", + rd_interval); + + if (rd_interval > 0 && dpcd[DP_DPCD_REV] < DP_DPCD_REV_14) + rd_interval *= 4 * USEC_PER_MSEC; + else + rd_interval = 100; + + return rd_interval; +} + /* * DisplayPort AUX channel */