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

[Cristian Ciocaltea]

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@xxxxxxxxxxxxx>
>> ---
>>  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"

Thanks for reviewing!

Regards,
Cristian