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.
v2: use USEC_PER_MSEC instead of MSEC_PER_SEC for clarity
Signed-off-by: Thierry Reding treding@nvidia.com --- drivers/gpu/drm/drm_dp_helper.c | 3 +++ include/drm/drm_dp_helper.h | 35 +++++++++++++++++++++++++++++++++ 2 files changed, 38 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c index 5b36e8e39ca7..4112570dbe67 100644 --- a/drivers/gpu/drm/drm_dp_helper.c +++ b/drivers/gpu/drm/drm_dp_helper.c @@ -382,6 +382,7 @@ static void drm_dp_link_reset(struct drm_dp_link *link) link->max_lanes = 0;
drm_dp_link_caps_reset(&link->caps); + link->aux_rd_interval = 0; link->edp = 0;
link->rate = 0; @@ -435,6 +436,8 @@ int drm_dp_link_probe(struct drm_dp_aux *aux, struct drm_dp_link *link) link->edp = edp_revs[value]; }
+ link->aux_rd_interval = drm_dp_aux_rd_interval(values); + link->rate = link->max_rate; link->lanes = link->max_lanes;
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h index 13c50e905205..e28b0941a8be 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, @@ -1229,6 +1232,36 @@ 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 */ @@ -1405,6 +1438,7 @@ void drm_dp_link_caps_copy(struct drm_dp_link_caps *dest, * @max_rate: maximum clock rate supported on the link * @max_lanes: maximum number of lanes supported on the link * @caps: capabilities supported on the link (see &drm_dp_link_caps) + * @aux_rd_interval: AUX read interval to use for training (in microseconds) * @edp: eDP revision (0x11: eDP 1.1, 0x12: eDP 1.2, ...) * @rate: currently configured link rate * @lanes: currently configured number of lanes @@ -1415,6 +1449,7 @@ struct drm_dp_link { unsigned int max_lanes;
struct drm_dp_link_caps caps; + unsigned int aux_rd_interval; unsigned char edp;
unsigned int rate;