linux-kernel - [PATCH v3 1/3] drm/bridge: ti-sn65dsi86: Support DisplayPort (non-eDP) mode

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Date:   Thu, 10 Mar 2022 15:22:25 +0000
From:   Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
To:     dri-devel@...ts.freedesktop.org, linux-renesas-soc@...r.kernel.org,
        Sam Ravnborg <sam@...nborg.org>,
        Douglas Anderson <dianders@...omium.org>,
        linux-kernel@...r.kernel.org
Cc:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Subject: [PATCH v3 1/3] drm/bridge: ti-sn65dsi86: Support DisplayPort (non-eDP) mode

From: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

Despite the SN65DSI86 being an eDP bridge, on some systems its output is
routed to a DisplayPort connector. Enable DisplayPort mode when the next
component in the display pipeline is detected as a DisplayPort
connector, and disable eDP features in that case.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Reworked to set bridge type based on the next bridge/connector.
Signed-off-by: Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
--
Changes since v1/RFC:
 - Rebased on top of "drm/bridge: ti-sn65dsi86: switch to
   devm_drm_of_get_bridge"
 - eDP/DP mode determined from the next bridge connector type.

Changes since v2:
 - Remove setting of Standard DP Scrambler Seed. (It's read-only).
 - Prevent setting DP_EDP_CONFIGURATION_SET in
   ti_sn_bridge_atomic_enable()
 - Use Doug's suggested text for disabling ASSR on DP mode.

 drivers/gpu/drm/bridge/ti-sn65dsi86.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi86.c b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
index c892ecba91c7..93b54fcba8ba 100644
--- a/drivers/gpu/drm/bridge/ti-sn65dsi86.c
+++ b/drivers/gpu/drm/bridge/ti-sn65dsi86.c
@@ -62,6 +62,7 @@
 #define SN_LN_ASSIGN_REG			0x59
 #define  LN_ASSIGN_WIDTH			2
 #define SN_ENH_FRAME_REG			0x5A
+#define  ASSR_CONTROL				BIT(0)
 #define  VSTREAM_ENABLE				BIT(3)
 #define  LN_POLRS_OFFSET			4
 #define  LN_POLRS_MASK				0xf0
@@ -93,6 +94,8 @@
 #define SN_DATARATE_CONFIG_REG			0x94
 #define  DP_DATARATE_MASK			GENMASK(7, 5)
 #define  DP_DATARATE(x)				((x) << 5)
+#define SN_TRAINING_SETTING_REG			0x95
+#define  SCRAMBLE_DISABLE			BIT(4)
 #define SN_ML_TX_MODE_REG			0x96
 #define  ML_TX_MAIN_LINK_OFF			0
 #define  ML_TX_NORMAL_MODE			BIT(0)
@@ -982,6 +985,17 @@ static int ti_sn_link_training(struct ti_sn65dsi86 *pdata, int dp_rate_idx,
 		goto exit;
 	}
 
+	/*
+	 * eDP panels use an Alternate Scrambler Seed compared to displays
+	 * hooked up via a full DisplayPort connector. SN65DSI86 only supports
+	 * the alternate scrambler seed, not the normal one, so the only way we
+	 * can support full DisplayPort displays is by fully turning off the
+	 * scrambler.
+	 */
+	if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort)
+		regmap_update_bits(pdata->regmap, SN_TRAINING_SETTING_REG,
+				   SCRAMBLE_DISABLE, SCRAMBLE_DISABLE);
+
 	/*
 	 * We'll try to link train several times.  As part of link training
 	 * the bridge chip will write DP_SET_POWER_D0 to DP_SET_POWER.  If
@@ -1046,12 +1060,13 @@ static void ti_sn_bridge_atomic_enable(struct drm_bridge *bridge,
 
 	/*
 	 * The SN65DSI86 only supports ASSR Display Authentication method and
-	 * this method is enabled by default. An eDP panel must support this
+	 * this method is enabled for eDP panels. An eDP panel must support this
 	 * authentication method. We need to enable this method in the eDP panel
 	 * at DisplayPort address 0x0010A prior to link training.
 	 */
-	drm_dp_dpcd_writeb(&pdata->aux, DP_EDP_CONFIGURATION_SET,
-			   DP_ALTERNATE_SCRAMBLER_RESET_ENABLE);
+	if (pdata->bridge.type == DRM_MODE_CONNECTOR_eDP)
+		drm_dp_dpcd_writeb(&pdata->aux, DP_EDP_CONFIGURATION_SET,
+				   DP_ALTERNATE_SCRAMBLER_RESET_ENABLE);
 
 	/* Set the DP output format (18 bpp or 24 bpp) */
 	val = (ti_sn_bridge_get_bpp(old_bridge_state) == 18) ? BPP_18_RGB : 0;
@@ -1215,6 +1230,8 @@ static int ti_sn_bridge_probe(struct auxiliary_device *adev,
 
 	pdata->bridge.funcs = &ti_sn_bridge_funcs;
 	pdata->bridge.of_node = np;
+	pdata->bridge.type = pdata->next_bridge->type == DRM_MODE_CONNECTOR_DisplayPort
+			   ? DRM_MODE_CONNECTOR_DisplayPort : DRM_MODE_CONNECTOR_eDP;
 
 	drm_bridge_add(&pdata->bridge);
 
-- 
2.32.0