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

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Message-ID: <66265f27-2314-40e3-a653-35e037685c1d@ti.com>
Date: Tue, 6 Feb 2024 16:10:38 -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

On 2/6/24 3:58 PM, Judith Mendez wrote:
> 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.

TBH I think it is a good idea to keep the flow the same as it
is for sdhci_am654_setup_delay_chain(). Unless you know of a
strong enough reason to change, I am leaning towards leaving the
patch as is.

> 
> ~ 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);
> 
>