[PATCH 03/12] drm/dp: add helpers for drm_dp_set_adjust_request_pre_emphasis and drm_dp_set_adjust_request_voltage

[Damian Kos <dkos@cadence.com>]

From: Quentin Schulz <quentin.schulz@free-electrons.com>

We already have functions to get the adjust request voltage and
pre-emphasis for a lane so it makes also sense to be able to set them so
that we can then easily update them via a DPCD write.

Add helpers for drm_dp_set_adjust_request_pre_emphasis and
drm_dp_set_adjust_request_voltage that respectively set the
pre-emphasis and voltage of a lane in the link status array.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Signed-off-by: Damian Kos <dkos@cadence.com>
---
 drivers/gpu/drm/drm_dp_helper.c |   28 ++++++++++++++++++++++++++++
 include/drm/drm_dp_helper.h     |    4 ++++
 2 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_helper.c b/drivers/gpu/drm/drm_dp_helper.c
index 3bc2e98..ca2f469 100644
--- a/drivers/gpu/drm/drm_dp_helper.c
+++ b/drivers/gpu/drm/drm_dp_helper.c
@@ -120,6 +120,34 @@ 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);
 
+void drm_dp_set_adjust_request_voltage(u8 link_status[DP_LINK_STATUS_SIZE],
+				       int lane, u8 volt)
+{
+	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
+	int s = ((lane & 1) ?
+		 DP_ADJUST_VOLTAGE_SWING_LANE1_SHIFT :
+		 DP_ADJUST_VOLTAGE_SWING_LANE0_SHIFT);
+	int idx = i - DP_LANE0_1_STATUS;
+
+	link_status[idx] &= ~(DP_ADJUST_VOLTAGE_SWING_LANE0_MASK << s);
+	link_status[idx] |= volt << s;
+}
+EXPORT_SYMBOL(drm_dp_set_adjust_request_voltage);
+
+void drm_dp_set_adjust_request_pre_emphasis(u8 link_status[DP_LINK_STATUS_SIZE],
+					    int lane, u8 pre_emphasis)
+{
+	int i = DP_ADJUST_REQUEST_LANE0_1 + (lane >> 1);
+	int s = ((lane & 1) ?
+		 DP_ADJUST_PRE_EMPHASIS_LANE1_SHIFT :
+		 DP_ADJUST_PRE_EMPHASIS_LANE0_SHIFT);
+	int idx = i - DP_LANE0_1_STATUS;
+
+	link_status[idx] &= ~(DP_ADJUST_PRE_EMPHASIS_LANE0_MASK << s);
+	link_status[idx] |= pre_emphasis << s;
+}
+EXPORT_SYMBOL(drm_dp_set_adjust_request_pre_emphasis);
+
 void drm_dp_link_train_clock_recovery_delay(const u8 dpcd[DP_RECEIVER_CAP_SIZE]) {
 	if (dpcd[DP_TRAINING_AUX_RD_INTERVAL] == 0)
 		udelay(100);
diff --git a/include/drm/drm_dp_helper.h b/include/drm/drm_dp_helper.h
index a488af0..6e64b2a 100644
--- a/include/drm/drm_dp_helper.h
+++ b/include/drm/drm_dp_helper.h
@@ -946,6 +946,10 @@ 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);
+void drm_dp_set_adjust_request_voltage(u8 link_status[DP_LINK_STATUS_SIZE],
+				       int lane, u8 volt);
+void drm_dp_set_adjust_request_pre_emphasis(u8 link_status[DP_LINK_STATUS_SIZE],
+					    int lane, u8 pre_emphasis);
 
 #define DP_BRANCH_OUI_HEADER_SIZE	0xc
 #define DP_RECEIVER_CAP_SIZE		0xf
-- 
1.7.1