[PATCH] mmc: sdhci-sprd: Fix minimum clock limit

[PATCH] mmc: sdhci-sprd: Fix minimum clock limit

[Wenchao Chen]

From: Wenchao Chen <wenchao.chen@unisoc.com>

The minimum clock supported by SPRD Host is 100000.

Signed-off-by: Wenchao Chen <wenchao.chen@unisoc.com>
---
 drivers/mmc/host/sdhci-sprd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
index 46c55ab4884c..b92a408f138d 100644
--- a/drivers/mmc/host/sdhci-sprd.c
+++ b/drivers/mmc/host/sdhci-sprd.c
@@ -309,7 +309,7 @@ static unsigned int sdhci_sprd_get_max_clock(struct sdhci_host *host)
 
 static unsigned int sdhci_sprd_get_min_clock(struct sdhci_host *host)
 {
-	return 400000;
+	return 100000;
 }
 
 static void sdhci_sprd_set_uhs_signaling(struct sdhci_host *host,
-- 
2.17.1

Re: [PATCH] mmc: sdhci-sprd: Fix minimum clock limit

[Adrian Hunter]

On 11/10/22 09:30, Wenchao Chen wrote:
> From: Wenchao Chen <wenchao.chen@unisoc.com>
> 
> The minimum clock supported by SPRD Host is 100000.

Commit messages are better if they say why a change
is being made.

This begs the question, was there a problem with 400 kHz?
Are there cases that benefit from this change?
Should it have a fixes tag,cc stable?

> 
> Signed-off-by: Wenchao Chen <wenchao.chen@unisoc.com>
> ---
>  drivers/mmc/host/sdhci-sprd.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
> index 46c55ab4884c..b92a408f138d 100644
> --- a/drivers/mmc/host/sdhci-sprd.c
> +++ b/drivers/mmc/host/sdhci-sprd.c
> @@ -309,7 +309,7 @@ static unsigned int sdhci_sprd_get_max_clock(struct sdhci_host *host)
>  
>  static unsigned int sdhci_sprd_get_min_clock(struct sdhci_host *host)
>  {
> -	return 400000;
> +	return 100000;
>  }
>  
>  static void sdhci_sprd_set_uhs_signaling(struct sdhci_host *host,

Re: [PATCH] mmc: sdhci-sprd: Fix minimum clock limit

[Wenchao Chen]

On Tue, Oct 11, 2022 at 2:45 PM Adrian Hunter <adrian.hunter@intel.com> wrote:
>
> On 11/10/22 09:30, Wenchao Chen wrote:
> > From: Wenchao Chen <wenchao.chen@unisoc.com>
> >
> > The minimum clock supported by SPRD Host is 100000.
>
> Commit messages are better if they say why a change
> is being made.
>
> This begs the question, was there a problem with 400 kHz?
> Are there cases that benefit from this change?
> Should it have a fixes tag,cc stable?
>

Code show as below:
static struct sdhci_ops sdhci_sprd_ops = {
...
.get_min_clock = sdhci_sprd_get_min_clock,
...
};

int sdhci_setup_host(struct sdhci_host *host)
{
...
if (host->ops->get_min_clock)
mmc->f_min = host->ops->get_min_clock(host);
...
}

static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
void mmc_rescan(struct work_struct *work)
{
...
for (i = 0; i < ARRAY_SIZE(freqs); i++) {
unsigned int freq = freqs[i];
if (freq > host->f_max) {
if (i + 1 < ARRAY_SIZE(freqs))
continue;
freq = host->f_max;
}
if (!mmc_rescan_try_freq(host, max(freq, host->f_min)))
break;
if (freqs[i] <= host->f_min) // If you start at 100K, you will try
400K, 300K, 200K, 100K.
break;
}
...
}

Our controller supports 100K. During the test, it was found that mmc_rescan
failed to scan the card at 400K, and did not try 300K, 200K, and 100K. After
modifying the minimum clock limit to 100K, the card scan was successful.

> >
> > Signed-off-by: Wenchao Chen <wenchao.chen@unisoc.com>
> > ---
> >  drivers/mmc/host/sdhci-sprd.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
> > index 46c55ab4884c..b92a408f138d 100644
> > --- a/drivers/mmc/host/sdhci-sprd.c
> > +++ b/drivers/mmc/host/sdhci-sprd.c
> > @@ -309,7 +309,7 @@ static unsigned int sdhci_sprd_get_max_clock(struct sdhci_host *host)
> >
> >  static unsigned int sdhci_sprd_get_min_clock(struct sdhci_host *host)
> >  {
> > -     return 400000;
> > +     return 100000;
> >  }
> >
> >  static void sdhci_sprd_set_uhs_signaling(struct sdhci_host *host,
>

Re: [PATCH] mmc: sdhci-sprd: Fix minimum clock limit

[Adrian Hunter]

On 11/10/22 11:40, Wenchao Chen wrote:
> On Tue, Oct 11, 2022 at 2:45 PM Adrian Hunter <adrian.hunter@intel.com> wrote:
>>
>> On 11/10/22 09:30, Wenchao Chen wrote:
>>> From: Wenchao Chen <wenchao.chen@unisoc.com>
>>>
>>> The minimum clock supported by SPRD Host is 100000.
>>
>> Commit messages are better if they say why a change
>> is being made.
>>
>> This begs the question, was there a problem with 400 kHz?
>> Are there cases that benefit from this change?
>> Should it have a fixes tag,cc stable?
>>
> 
> Code show as below:
> static struct sdhci_ops sdhci_sprd_ops = {
> ...
> .get_min_clock = sdhci_sprd_get_min_clock,
> ...
> };
> 
> int sdhci_setup_host(struct sdhci_host *host)
> {
> ...
> if (host->ops->get_min_clock)
> mmc->f_min = host->ops->get_min_clock(host);
> ...
> }
> 
> static const unsigned freqs[] = { 400000, 300000, 200000, 100000 };
> void mmc_rescan(struct work_struct *work)
> {
> ...
> for (i = 0; i < ARRAY_SIZE(freqs); i++) {
> unsigned int freq = freqs[i];
> if (freq > host->f_max) {
> if (i + 1 < ARRAY_SIZE(freqs))
> continue;
> freq = host->f_max;
> }
> if (!mmc_rescan_try_freq(host, max(freq, host->f_min)))
> break;
> if (freqs[i] <= host->f_min) // If you start at 100K, you will try
> 400K, 300K, 200K, 100K.
> break;
> }
> ...
> }
> 
> Our controller supports 100K. During the test, it was found that mmc_rescan
> failed to scan the card at 400K, and did not try 300K, 200K, and 100K. After
> modifying the minimum clock limit to 100K, the card scan was successful.

Please add those last 3 lines to the commit message, then you can add:

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

Also please consider adding a Fixes: tag.

> 
>>>
>>> Signed-off-by: Wenchao Chen <wenchao.chen@unisoc.com>
>>> ---
>>>  drivers/mmc/host/sdhci-sprd.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/mmc/host/sdhci-sprd.c b/drivers/mmc/host/sdhci-sprd.c
>>> index 46c55ab4884c..b92a408f138d 100644
>>> --- a/drivers/mmc/host/sdhci-sprd.c
>>> +++ b/drivers/mmc/host/sdhci-sprd.c
>>> @@ -309,7 +309,7 @@ static unsigned int sdhci_sprd_get_max_clock(struct sdhci_host *host)
>>>
>>>  static unsigned int sdhci_sprd_get_min_clock(struct sdhci_host *host)
>>>  {
>>> -     return 400000;
>>> +     return 100000;
>>>  }
>>>
>>>  static void sdhci_sprd_set_uhs_signaling(struct sdhci_host *host,
>>