[Intel-gfx] [PATCH v2 1/8] drm/dp: add drm_dp_128b132b_read_aux_rd_interval()

Jani Nikula
2022-02-03T09:04:15Z

The DP 2.0 errata changes DP_128B132B_TRAINING_AUX_RD_INTERVAL (DPCD
0x2216) completely. Add a new function to read that. Follow-up will need
to clean up existing functions.

v2: fix reversed interpretation of bit 7 meaning (Uma)

Cc: Uma Shankar <uma.shankar@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
drivers/gpu/drm/dp/drm_dp.c | 20 ++++++++++++++++++++
include/drm/dp/drm_dp_helper.h | 3 +++
2 files changed, 23 insertions(+)

diff --git a/drivers/gpu/drm/dp/drm_dp.c b/drivers/gpu/drm/dp/drm_dp.c
index 6d43325acca5..52c6da510142 100644
--- a/drivers/gpu/drm/dp/drm_dp.c
+++ b/drivers/gpu/drm/dp/drm_dp.c
@@ -281,6 +281,26 @@ int drm_dp_read_channel_eq_delay(struct drm_dp_aux *aux, const u8 dpcd[DP_RECEIV
}
EXPORT_SYMBOL(drm_dp_read_channel_eq_delay);

+/* Per DP 2.0 Errata */
+int drm_dp_128b132b_read_aux_rd_interval(struct drm_dp_aux *aux)
+{
+ int unit;
+ u8 val;
+
+ if (drm_dp_dpcd_readb(aux, DP_128B132B_TRAINING_AUX_RD_INTERVAL, &val) != 1) {
+ drm_err(aux->drm_dev, "%s: failed rd interval read\n",
+ aux->name);
+ /* default to max */
+ val = DP_128B132B_TRAINING_AUX_RD_INTERVAL_MASK;
+ }
+
+ unit = (val & DP_128B132B_TRAINING_AUX_RD_INTERVAL_1MS_UNIT) ? 1 : 2;
+ val &= DP_128B132B_TRAINING_AUX_RD_INTERVAL_MASK;
+
+ return (val + 1) * unit * 1000;
+}
+EXPORT_SYMBOL(drm_dp_128b132b_read_aux_rd_interval);
+
void drm_dp_link_train_clock_recovery_delay(const struct drm_dp_aux *aux,
const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
diff --git a/include/drm/dp/drm_dp_helper.h b/include/drm/dp/drm_dp_helper.h
index 98d020835b49..aa73dfc817ff 100644
--- a/include/drm/dp/drm_dp_helper.h
+++ b/include/drm/dp/drm_dp_helper.h
@@ -1112,6 +1112,7 @@ struct drm_panel;
# define DP_UHBR13_5 (1 << 2)

#define DP_128B132B_TRAINING_AUX_RD_INTERVAL 0x2216 /* 2.0 */
+# define DP_128B132B_TRAINING_AUX_RD_INTERVAL_1MS_UNIT (1 << 7)
# define DP_128B132B_TRAINING_AUX_RD_INTERVAL_MASK 0x7f
# define DP_128B132B_TRAINING_AUX_RD_INTERVAL_400_US 0x00
# define DP_128B132B_TRAINING_AUX_RD_INTERVAL_4_MS 0x01
@@ -1549,6 +1550,8 @@ void drm_dp_link_train_channel_eq_delay(const struct drm_dp_aux *aux,
void drm_dp_lttpr_link_train_channel_eq_delay(const struct drm_dp_aux *aux,
const u8 caps[DP_LTTPR_PHY_CAP_SIZE]);

+int drm_dp_128b132b_read_aux_rd_interval(struct drm_dp_aux *aux);
+
u8 drm_dp_link_rate_to_bw_code(int link_rate);
int drm_dp_bw_code_to_link_rate(u8 link_bw);

--
2.30.2