From: Thierry Reding <treding@xxxxxxxxxx>
If the transmitter supports pre-emphasis post cursor2 the sink will
request adjustments in a similar way to how it requests adjustments to
the voltage swing and pre-emphasis settings.
Add a helper to extract these adjustments on a per-lane basis from the
DPCD link status.
Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
---
drivers/gpu/drm/drm_dp_helper.c | 10 ++++++++++
include/drm/drm_dp_helper.h | 10 ++++++++++
2 files changed, 20 insertions(+)
diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index dabac772dfc3..f1a7f18ab795 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -118,6 +118,16 @@ u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SI
}
EXPORT_SYMBOL(drm_dp_get_adjust_request_pre_emphasis);
+u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE],
+ unsigned int lane)
+{
+ unsigned int offset = DP_ADJUST_REQUEST_POST_CURSOR2;
+ u8 value = dp_link_status(link_status, offset);
+
+ return (value >> (lane << 1)) & 0x3;
+}
+EXPORT_SYMBOL(drm_dp_get_adjust_request_post_cursor);
+
void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE])
{
unsigned int min = drm_dp_aux_rd_interval(dpcd);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index 8213f1c53f9b..4c7badcde945 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -512,6 +512,14 @@
# define DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT 6
#define DP_ADJUST_REQUEST_POST_CURSOR2 0x20c
+# define DP_ADJUST_POST_CURSOR2_LANE0_MASK 0x03
+# define DP_ADJUST_POST_CURSOR2_LANE0_SHIFT 0
+# define DP_ADJUST_POST_CURSOR2_LANE1_MASK 0x0c
+# define DP_ADJUST_POST_CURSOR2_LANE1_SHIFT 2
+# define DP_ADJUST_POST_CURSOR2_LANE2_MASK 0x30
+# define DP_ADJUST_POST_CURSOR2_LANE2_SHIFT 4
+# define DP_ADJUST_POST_CURSOR2_LANE3_MASK 0xc0
+# define DP_ADJUST_POST_CURSOR2_LANE3_SHIFT 6
#define DP_TEST_REQUEST 0x218
# define DP_TEST_LINK_TRAINING (1 << 0)
@@ -892,6 +900,8 @@ u8 drm_dp_get_adjust_request_voltage(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane);
u8 drm_dp_get_adjust_request_pre_emphasis(const u8 link_status[DP_LINK_STATUS_SIZE],
int lane);
+u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE],
+ unsigned int lane);
#define DP_BRANCH_OUI_HEADER_SIZE 0xc
#define DP_RECEIVER_CAP_SIZE 0xf
--
2.15.1
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