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

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Message-ID: <20250306-masked-voracious-octopus-be05b8@houat>
Date: Thu, 6 Mar 2025 14:35:19 +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

On Tue, Mar 04, 2025 at 02:04:18PM +0200, Cristian Ciocaltea wrote:
> Hi Maxime,
> 
> On 3/4/25 10:13 AM, Maxime Ripard wrote:
> > 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.
> 
> The rate coming from rk_hdptx_phy_power_on() is in hHz, since it passed
> via dw_hdmi_qp_rockchip_encoder_enable() as
> 
>   phy_set_bus_width(hdmi->phy, div_u64(rate, 100));
> 
> > 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?
> 
> This stems from the ropll_tmds_cfg table containing the configuration
> params for the supported rates which requires the search keys to be
> provided in hHz rather than Hz.
> 
> I agree this is nothing but confusing, that's why I fixed this up in
> "phy: rockchip: samsung-hdptx: Avoid Hz-hHz unit conversion overhead"

Yeah, sorry, I noticed it after sending the review. Still, I'd advise to
put that patch first, it's a bit weird to add more patch we're going to
rework later on.

Maxime

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