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

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Message-ID: <2753758.X9hSmTKtgW@diego>
Date: Wed, 15 Oct 2025 17:44:01 +0200
From: Heiko Stübner <heiko@...ech.de>
To: Sandy Huang <hjc@...k-chips.com>, 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>,
 Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
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: Re: [PATCH v4 2/6] drm/bridge: dw-hdmi-qp: Fixup timer base setup

Am Mittwoch, 3. September 2025, 20:51:00 Mitteleuropäische Sommerzeit schrieb Cristian Ciocaltea:
> 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>

Reviewed-by: Heiko Stuebner <heiko@...ech.de>

This _does_ look ok to me, but as that touches the main bridge, could
we get a 2nd set of eyes?

Thanks
Heiko

> ---
>  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,
> 
>