linux-kernel - [PATCH v4 2/6] drm/bridge: dw-hdmi-qp: Fixup timer base setup

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Message-Id: <20250903-rk3588-hdmi-cec-v4-2-fa25163c4b08@collabora.com>
Date: Wed, 03 Sep 2025 21:51:00 +0300
From: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
To: Sandy Huang <hjc@...k-chips.com>, 
 Heiko Stübner <heiko@...ech.de>, 
 Andy Yan <andy.yan@...k-chips.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>, 
 Andrzej Hajda <andrzej.hajda@...el.com>, 
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>, 
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Cc: kernel@...labora.com, dri-devel@...ts.freedesktop.org, 
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org, 
 linux-kernel@...r.kernel.org
Subject: [PATCH v4 2/6] drm/bridge: dw-hdmi-qp: Fixup timer base setup

Currently the TIMER_BASE_CONFIG0 register gets initialized to a fixed
value as initially found in vendor driver code supporting the RK3588
SoC.  As a matter of fact the value matches the rate of the HDMI TX
reference clock, which is roughly 428.57 MHz.

However, on RK3576 SoC that rate is slightly lower, i.e. 396.00 MHz, and
the incorrect register configuration breaks CEC functionality.

Set the timer base according to the actual reference clock rate that
shall be provided by the platform driver.  Otherwise fallback to the
vendor default.

While at it, also drop the unnecessary empty lines in
dw_hdmi_qp_init_hw().

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c | 12 +++++++++---
 include/drm/bridge/dw_hdmi_qp.h              |  1 +
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
index fc98953672b6fb388d05201e280d24b8f214498a..4ba7b339eff62592aa748429a3bfca82494679d1 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi-qp.c
@@ -161,6 +161,7 @@ struct dw_hdmi_qp {
 		void *data;
 	} phy;
 
+	unsigned long ref_clk_rate;
 	struct regmap *regm;
 
 	unsigned long tmds_char_rate;
@@ -1210,13 +1211,11 @@ static void dw_hdmi_qp_init_hw(struct dw_hdmi_qp *hdmi)
 {
 	dw_hdmi_qp_write(hdmi, 0, MAINUNIT_0_INT_MASK_N);
 	dw_hdmi_qp_write(hdmi, 0, MAINUNIT_1_INT_MASK_N);
-	dw_hdmi_qp_write(hdmi, 428571429, TIMER_BASE_CONFIG0);
+	dw_hdmi_qp_write(hdmi, hdmi->ref_clk_rate, TIMER_BASE_CONFIG0);
 
 	/* Software reset */
 	dw_hdmi_qp_write(hdmi, 0x01, I2CM_CONTROL0);
-
 	dw_hdmi_qp_write(hdmi, 0x085c085c, I2CM_FM_SCL_CONFIG0);
-
 	dw_hdmi_qp_mod(hdmi, 0, I2CM_FM_EN, I2CM_INTERFACE_CONTROL0);
 
 	/* Clear DONE and ERROR interrupts */
@@ -1262,6 +1261,13 @@ struct dw_hdmi_qp *dw_hdmi_qp_bind(struct platform_device *pdev,
 	hdmi->phy.ops = plat_data->phy_ops;
 	hdmi->phy.data = plat_data->phy_data;
 
+	if (plat_data->ref_clk_rate) {
+		hdmi->ref_clk_rate = plat_data->ref_clk_rate;
+	} else {
+		hdmi->ref_clk_rate = 428571429;
+		dev_warn(dev, "Set ref_clk_rate to vendor default\n");
+	}
+
 	dw_hdmi_qp_init_hw(hdmi);
 
 	ret = devm_request_threaded_irq(dev, plat_data->main_irq,
diff --git a/include/drm/bridge/dw_hdmi_qp.h b/include/drm/bridge/dw_hdmi_qp.h
index b4a9b739734ec7b67013b683fe6017551aa19172..76ecf31301997718604a05f70ce9eab8695e26b5 100644
--- a/include/drm/bridge/dw_hdmi_qp.h
+++ b/include/drm/bridge/dw_hdmi_qp.h
@@ -24,6 +24,7 @@ struct dw_hdmi_qp_plat_data {
 	void *phy_data;
 	int main_irq;
 	int cec_irq;
+	unsigned long ref_clk_rate;
 };
 
 struct dw_hdmi_qp *dw_hdmi_qp_bind(struct platform_device *pdev,

-- 
2.51.0