Re: [PATCH 2/4] mmc: sdhci-cadence6: program PHONY_DQS_TIMING for extended-read DDR

[Adrian Hunter]

On 22/09/2026 14:12, tze.yee.ng@xxxxxxxxxx wrote:
> From: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>
> 
> The SD6HC PHY left PHONY_DQS_TIMING (phy_ctrl_reg[9:4]) at 0 in all
> modes. Per the Cadence DLL PHY documentation it must be the rebar (RE#)
> pulse width in clk_phy cycles minus 1 in extended read mode, and 0
> otherwise. Leaving it 0 in extended-read DDR duplicates one DDR edge
> (the silent odd/even edge-capture defect).
> 
> This controller's rebar pulse is a fixed 2 clk_phy cycles, so extended-
> read DDR needs 1; confirmed on DDR50 hardware (1 captures both beats, 2
> corrupts reads). Derive it from the extended-read-mode state and apply
> it only in DDR modes, since SDR extended-read samples a single edge and
> is unaffected. This is generic to any SD6HC-PHY SoC, so it is kept
> separate from the per-SoC read-path tuning.
> 
> Signed-off-by: Tze Yee Ng <tze.yee.ng@xxxxxxxxxx>

Acked-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>

> ---
>  drivers/mmc/host/sdhci-cadence-phy-v6.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-cadence-phy-v6.c b/drivers/mmc/host/sdhci-cadence-phy-v6.c
> index 35f35ef9c710..84592ae42762 100644
> --- a/drivers/mmc/host/sdhci-cadence-phy-v6.c
> +++ b/drivers/mmc/host/sdhci-cadence-phy-v6.c
> @@ -90,6 +90,9 @@
>  #define SDHCI_CDNS6_PHY_CTRL_REG			0x2080
>  #define   SDHCI_CDNS6_PHY_CTRL_PHONY_DQS_TIMING			GENMASK(9, 4)
>  
> +/* Width of this controller's rebar (RE#) pulse in clk_phy cycles. */
> +#define SDHCI_CDNS6_PHY_REBAR_PULSE_CYCLES	2
> +
>  /* Default PHY settings */
>  #define SDHCI_CDNS6_PHY_DEFAULT_IOCELL_DELAY		2500
>  #define SDHCI_CDNS6_PHY_DEFAULT_DELAY_ELEMENT		24
> @@ -143,6 +146,9 @@ struct sdhci_cdns6_phy {
>  	bool cp_use_phony_dqs;		/* bit [20] */
>  	bool cp_use_phony_dqs_cmd;	/* bit [19] */
>  
> +	/* PHY_CTRL register fields */
> +	u32 cp_phony_dqs_timing;
> +
>  	/* HRS07 register - IO delay Information */
>  	u8 sdhc_rw_compensate;		/* bits [20:16] */
>  	u8 sdhc_idelay_val;		/* bits [4:0] */
> @@ -517,6 +523,13 @@ static void sdhci_cdns6_phy_calc_dat_in(struct sdhci_cdns6_phy *phy)
>  	if (phy->mode == MMC_TIMING_MMC_HS200)
>  		phy->cp_read_dqs_delay = phy->hs200_tune_val;
>  
> +	if (phy->sdhc_extended_rd_mode &&
> +	    (phy->mode == MMC_TIMING_UHS_DDR50 ||
> +	     phy->mode == MMC_TIMING_MMC_DDR52))
> +		phy->cp_phony_dqs_timing = SDHCI_CDNS6_PHY_REBAR_PULSE_CYCLES - 1;
> +	else
> +		phy->cp_phony_dqs_timing = 0;
> +
>  	if (strobe_dat) {
>  		/* dqs loopback input via IO cell */
>  		hcsdclkadj += phy->iocell_input_delay;
> @@ -715,6 +728,8 @@ int sdhci_cdns6_phy_init(struct sdhci_cdns_priv *priv)
>  
>  	reg = sdhci_cdns6_read_phy_reg(priv, SDHCI_CDNS6_PHY_CTRL_REG);
>  	reg &= ~SDHCI_CDNS6_PHY_CTRL_PHONY_DQS_TIMING;
> +	reg |= FIELD_PREP(SDHCI_CDNS6_PHY_CTRL_PHONY_DQS_TIMING,
> +			  phy->cp_phony_dqs_timing);
>  	sdhci_cdns6_write_phy_reg(priv, SDHCI_CDNS6_PHY_CTRL_REG, reg);
>  
>  	/*