linux-kernel - [PATCH v11 05/14] drm/bridge: cdns-dsi: Wait for Clk and Data Lanes to be ready

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Message-Id: <20250329113925.68204-6-aradhya.bhatia@linux.dev>
Date: Sat, 29 Mar 2025 17:09:16 +0530
From: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
	Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Cc: Nishanth Menon <nm@...com>,
	Vignesh Raghavendra <vigneshr@...com>,
	Devarsh Thakkar <devarsht@...com>,
	Praneeth Bajjuri <praneeth@...com>,
	Udit Kumar <u-kumar1@...com>,
	Jayesh Choudhary <j-choudhary@...com>,
	Alexander Sverdlin <alexander.sverdlin@...mens.com>,
	Dominik Haller <d.haller@...tec.de>,
	DRI Development List <dri-devel@...ts.freedesktop.org>,
	Linux Kernel List <linux-kernel@...r.kernel.org>,
	Aradhya Bhatia <aradhya.bhatia@...ux.dev>,
	stable@...r.kernel.org
Subject: [PATCH v11 05/14] drm/bridge: cdns-dsi: Wait for Clk and Data Lanes to be ready

From: Aradhya Bhatia <a-bhatia1@...com>

Once the DSI Link and DSI Phy are initialized, the code needs to wait
for Clk and Data Lanes to be ready, before continuing configuration.
This is in accordance with the DSI Start-up procedure, found in the
Technical Reference Manual of Texas Instrument's J721E SoC[0] which
houses this DSI TX controller.

If the previous bridge (or crtc/encoder) are configured pre-maturely,
the input signal FIFO gets corrupt. This introduces a color-shift on the
display.

Allow the driver to wait for the clk and data lanes to get ready during
DSI enable.

[0]: See section 12.6.5.7.3 "Start-up Procedure" in J721E SoC TRM
     TRM Link: http://www.ti.com/lit/pdf/spruil1

Fixes: e19233955d9e ("drm/bridge: Add Cadence DSI driver")
Cc: stable@...r.kernel.org
Tested-by: Dominik Haller <d.haller@...tec.de>
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Tested-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Signed-off-by: Aradhya Bhatia <a-bhatia1@...com>
Signed-off-by: Aradhya Bhatia <aradhya.bhatia@...ux.dev>
---
 drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
index 741d676b8266..93c3d5f1651d 100644
--- a/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
+++ b/drivers/gpu/drm/bridge/cadence/cdns-dsi-core.c
@@ -776,7 +776,7 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge,
 	struct drm_connector *connector;
 	unsigned long tx_byte_period;
 	struct cdns_dsi_cfg dsi_cfg;
-	u32 tmp, reg_wakeup, div;
+	u32 tmp, reg_wakeup, div, status;
 	int nlanes;
 
 	if (WARN_ON(pm_runtime_get_sync(dsi->base.dev) < 0))
@@ -796,6 +796,19 @@ static void cdns_dsi_bridge_atomic_enable(struct drm_bridge *bridge,
 	cdns_dsi_hs_init(dsi);
 	cdns_dsi_init_link(dsi);
 
+	/*
+	 * Now that the DSI Link and DSI Phy are initialized,
+	 * wait for the CLK and Data Lanes to be ready.
+	 */
+	tmp = CLK_LANE_RDY;
+	for (int i = 0; i < nlanes; i++)
+		tmp |= DATA_LANE_RDY(i);
+
+	if (readl_poll_timeout(dsi->regs + MCTL_MAIN_STS, status,
+			       (tmp == (status & tmp)), 100, 500000))
+		dev_err(dsi->base.dev,
+			"Timed Out: DSI-DPhy Clock and Data Lanes not ready.\n");
+
 	writel(HBP_LEN(dsi_cfg.hbp) | HSA_LEN(dsi_cfg.hsa),
 	       dsi->regs + VID_HSIZE1);
 	writel(HFP_LEN(dsi_cfg.hfp) | HACT_LEN(dsi_cfg.hact),
-- 
2.34.1