On Tue, 2019-10-15 at 16:35 +0200, Thierry Reding wrote:
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);
Do you think it might be worth clamping the value to 4 here?
- if (rd_interval > 0 && dpcd[DP_DPCD_REV] < DP_DPCD_REV_14)
Also small nit pick: you can just use rd_interval instead of rd_interval > 0
rd_interval *= 4 * USEC_PER_MSEC;- else
rd_interval = 100;- return rd_interval;
+}
/*
- DisplayPort AUX channel
*/