[Intel-gfx] [PATCH v3 04/13] drm/dp: add helper for extracting adjust 128b/132b TX FFE preset

Jani Nikula
2021-09-09T12:52:45Z

The DP 2.0 128b/132b channel coding uses TX FFE presets instead of
vswing and pre-emphasis.

Cc: dri-devel@lists.freedesktop.org
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
---
drivers/gpu/drm/drm_dp_helper.c | 14 ++++++++++++++
include/drm/drm_dp_helper.h | 2 ++
2 files changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 2e74b02ed96b..4d0d1e8e51fa 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -130,6 +130,20 @@ 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);

+/* DP 2.0 128b/132b */
+u8 drm_dp_get_adjust_tx_ffe_preset(const u8 link_status[DP_LINK_STATUS_SIZE],
+ int lane)
+{
+ int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
+ int s = ((lane & 1) ?
+ DP_ADJUST_TX_FFE_PRESET_LANE1_SHIFT :
+ DP_ADJUST_TX_FFE_PRESET_LANE0_SHIFT);
+ u8 l = dp_link_status(link_status, i);
+
+ return (l >> s) & 0xf;
+}
+EXPORT_SYMBOL(drm_dp_get_adjust_tx_ffe_preset);
+
u8 drm_dp_get_adjust_request_post_cursor(const u8 link_status[DP_LINK_STATUS_SIZE],
unsigned int lane)
{
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index f3a61341011d..3ee0b3ffb8a5 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -1494,6 +1494,8 @@ 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_tx_ffe_preset(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);

--
2.30.2