linux-kernel - [PATCH 03/12] drm/dp: add helpers for drm_dp_set_adjust_request_pre_emphasis and drm_dp_set_adjust_request

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Date:   Tue, 3 Jul 2018 11:02:14 +0100
From:   Damian Kos <dkos@...ence.com>
To:     David Airlie <airlied@...ux.ie>, Rob Herring <robh+dt@...nel.org>,
        "Mark Rutland" <mark.rutland@....com>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        Sandy Huang <hjc@...k-chips.com>,
        Heiko Stübner <heiko@...ech.de>,
        Damian Kos <dkos@...ence.com>,
        <dri-devel@...ts.freedesktop.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-rockchip@...ts.infradead.org>
CC:     <ltyrala@...ence.com>, <pgaj@...ence.com>, <stelford@...ence.com>,
        "Quentin Schulz" <quentin.schulz@...e-electrons.com>
Subject: [PATCH 03/12] drm/dp: add helpers for drm_dp_set_adjust_request_pre_emphasis and drm_dp_set_adjust_request_voltage

From: Quentin Schulz <quentin.schulz@...e-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@...e-electrons.com>
Signed-off-by: Damian Kos <dkos@...ence.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