linux-kernel - Re: [PATCH v1 2/5] mmc: sdhci_am654: Write ITAPDLY for DDR52 timing

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Date: Thu, 1 Feb 2024 13:36:40 -0600
From: Andrew Davis <afd@...com>
To: Judith Mendez <jm@...com>, Ulf Hansson <ulf.hansson@...aro.org>
CC: Adrian Hunter <adrian.hunter@...el.com>, <linux-mmc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, Randolph Sapp <rs@...com>,
        Vignesh
 Raghavendra <vigneshr@...com>
Subject: Re: [PATCH v1 2/5] mmc: sdhci_am654: Write ITAPDLY for DDR52 timing

On 1/31/24 3:50 PM, Judith Mendez wrote:
> For DDR52 timing, DLL is enabled but tuning is not carried
> out, therefore the ITAPDLY value in PHY CTRL 4 register is
> not correct. Fix this by writing ITAPDLY after enabling DLL.
> 
> Fixes: a161c45f2979 ("mmc: sdhci_am654: Enable DLL only for some speed modes")
> Signed-off-by: Judith Mendez <jm@...com>
> ---
>   drivers/mmc/host/sdhci_am654.c | 27 +++++++++++++++------------
>   1 file changed, 15 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci_am654.c b/drivers/mmc/host/sdhci_am654.c
> index a3798c9912f6..ff18a274b6f2 100644
> --- a/drivers/mmc/host/sdhci_am654.c
> +++ b/drivers/mmc/host/sdhci_am654.c
> @@ -170,7 +170,19 @@ struct sdhci_am654_driver_data {
>   #define DLL_CALIB	(1 << 4)
>   };
>   
> -static void sdhci_am654_setup_dll(struct sdhci_host *host, unsigned int clock)
> +static void sdhci_am654_write_itapdly(struct sdhci_am654_data *sdhci_am654,
> +				      u32 itapdly)

This patch is confusing, looks like you switched the place of these two
functions, but diff is not really liking that. You can mess with
--diff-algorithm and the like to get a more readable patch. But in
this case why switch their spots at all?

Seems to be so you can call sdhci_am654_write_itapdly() from
sdhci_am654_setup_dll() without a forward declaration, instead
why not just call sdhci_am654_write_itapdly() after calling
sdhci_am654_setup_dll() below. That also saves to from having
to pass in `timing` to sdhci_am654_write_itapdly() just to
have it pass it right through to sdhci_am654_setup_dll().

Andrew

> +{
> +	/* Set ITAPCHGWIN before writing to ITAPDLY */
> +	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPCHGWIN_MASK,
> +			   0x1 << ITAPCHGWIN_SHIFT);
> +	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPDLYSEL_MASK,
> +			   itapdly << ITAPDLYSEL_SHIFT);
> +	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPCHGWIN_MASK, 0);
> +}
> +
> +static void sdhci_am654_setup_dll(struct sdhci_host *host, unsigned int clock,
> +				  unsigned char timing)
>   {
>   	struct sdhci_pltfm_host *pltfm_host = sdhci_priv(host);
>   	struct sdhci_am654_data *sdhci_am654 = sdhci_pltfm_priv(pltfm_host);
> @@ -236,17 +248,8 @@ static void sdhci_am654_setup_dll(struct sdhci_host *host, unsigned int clock)
>   		dev_err(mmc_dev(host->mmc), "DLL failed to relock\n");
>   		return;
>   	}
> -}
>   
> -static void sdhci_am654_write_itapdly(struct sdhci_am654_data *sdhci_am654,
> -				      u32 itapdly)
> -{
> -	/* Set ITAPCHGWIN before writing to ITAPDLY */
> -	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPCHGWIN_MASK,
> -			   1 << ITAPCHGWIN_SHIFT);
> -	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPDLYSEL_MASK,
> -			   itapdly << ITAPDLYSEL_SHIFT);
> -	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, ITAPCHGWIN_MASK, 0);
> +	sdhci_am654_write_itapdly(sdhci_am654, sdhci_am654->itap_del_sel[timing]);
>   }
>   
>   static void sdhci_am654_setup_delay_chain(struct sdhci_am654_data *sdhci_am654,
> @@ -298,7 +301,7 @@ static void sdhci_am654_set_clock(struct sdhci_host *host, unsigned int clock)
>   	regmap_update_bits(sdhci_am654->base, PHY_CTRL4, mask, val);
>   
>   	if (timing > MMC_TIMING_UHS_SDR25 && clock >= CLOCK_TOO_SLOW_HZ) {
> -		sdhci_am654_setup_dll(host, clock);
> +		sdhci_am654_setup_dll(host, clock, timing);
>   		sdhci_am654->dll_enable = true;
>   	} else {
>   		sdhci_am654_setup_delay_chain(sdhci_am654, timing);