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

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Date: Tue, 6 Feb 2024 15:58:15 -0600
From: Judith Mendez <jm@...com>
To: Andrew Davis <afd@...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

Hi Andrew,

On 2/1/24 1:36 PM, Andrew Davis wrote:
> 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().

Really the only reason I did this is because we call
sdhci_am654_write_itapdly() in sdhci_am654_setup_delay_chain and
I wanted to keep the flow for setting up DLL the same.
I agree the patch looks confusing, so I will fix this for v2.

~ Judith

> 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);