linux-kernel - Re: [PATCH v4 03/12] phy: rockchip: samsung-hdptx: Fix clock ratio setup

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Message-ID: <20250304-small-mindful-mongrel-bd6f8b@houat>
Date: Tue, 4 Mar 2025 09:13:20 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
Cc: Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Heiko Stuebner <heiko@...ech.de>, 
	Algea Cao <algea.cao@...k-chips.com>, Sandor Yu <Sandor.yu@....com>, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, kernel@...labora.com, linux-kernel@...r.kernel.org, 
	linux-phy@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org, 
	linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v4 03/12] phy: rockchip: samsung-hdptx: Fix clock ratio
 setup

Hi,

On Tue, Mar 04, 2025 at 03:44:02AM +0200, Cristian Ciocaltea wrote:
> The switch from 1/10 to 1/40 clock ratio must happen when exceeding the
> 340 MHz rate limit of HDMI 1.4, i.e. when entering the HDMI 2.0 domain,
> and not before.
> 
> While at it, introduce a define for this rate limit constant.
> 
> Fixes: 553be2830c5f ("phy: rockchip: Add Samsung HDMI/eDP Combo PHY driver")
> Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@...labora.com>
> ---
>  drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> index f88369864c50e4563834ccbb26f1f9f440e99271..cf2c3a46604cb9d8c26fe5ec8346904e0b62848f 100644
> --- a/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> +++ b/drivers/phy/rockchip/phy-rockchip-samsung-hdptx.c
> @@ -320,6 +320,7 @@
>  #define LN3_TX_SER_RATE_SEL_HBR2_MASK	BIT(3)
>  #define LN3_TX_SER_RATE_SEL_HBR3_MASK	BIT(2)
>  
> +#define HDMI14_MAX_RATE			340000000
>  #define HDMI20_MAX_RATE			600000000
>  
>  enum dp_link_rate {
> @@ -1072,7 +1073,7 @@ static int rk_hdptx_ropll_tmds_mode_config(struct rk_hdptx_phy *hdptx,
>  
>  	regmap_write(hdptx->regmap, LNTOP_REG(0200), 0x06);
>  
> -	if (rate >= 3400000) {
> +	if (rate > HDMI14_MAX_RATE / 100) {

The rate seems to come from rk_hdptx_phy_power_on and eventually from
tmds_char_rate in the PHY config options, so its rate is in Hertz.
HDMI14_MAX_RATE and HDMI20_MAX_RATE are both defined in Hertz as well.
It seems super odd to mee that you then convert HDMI14_MAX_RATE to hHz?

Maxime

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