[U-Boot] [PATCH V3 3/6] mmc: tmio: Keep generating clock when clock are enabled

[Marek Vasut]

On 11/27/2018 04:43 AM, Masahiro Yamada wrote:
> On Wed, Nov 14, 2018 at 8:44 AM Marek Vasut <marek.vasut at gmail.com> wrote:
>>
>> The TMIO core has a feature where it can automatically disable clock output
>> when the bus is not in use. While this is useful, it also interferes with
>> switching the bus to 1.8V and other background tasks of the SD/MMC cards,
>> which require clock to be enabled.
>>
>> This patch respects the mmc->clk_disable and only disables the clock when
>> the MMC core requests it. Otherwise the clock are continuously generated
>> on the bus.
>>
>> Signed-off-by: Marek Vasut <marek.vasut+renesas at gmail.com>
>> Cc: Masahiro Yamada <yamada.masahiro at socionext.com>
>> ---
>>  drivers/mmc/tmio-common.c | 10 ++++++++--
>>  1 file changed, 8 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/tmio-common.c b/drivers/mmc/tmio-common.c
>> index 424b60ce52..fad2816ca5 100644
>> --- a/drivers/mmc/tmio-common.c
>> +++ b/drivers/mmc/tmio-common.c
>> @@ -612,10 +612,16 @@ static void tmio_sd_set_clk_rate(struct tmio_sd_priv *priv,
>>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
>>
>>         tmp &= ~TMIO_SD_CLKCTL_DIV_MASK;
>> -       tmp |= val | TMIO_SD_CLKCTL_OFFEN;
>> +       tmp |= val;
>>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
>>
>> -       tmp |= TMIO_SD_CLKCTL_SCLKEN;
>> +       if (!mmc->clk_disable) {
>> +               tmp &= ~TMIO_SD_CLKCTL_OFFEN;
>> +               tmp |= TMIO_SD_CLKCTL_SCLKEN;
>> +       } else {
>> +               tmp |= TMIO_SD_CLKCTL_OFFEN;
>> +               tmp &= ~TMIO_SD_CLKCTL_SCLKEN;
>> +       }
>>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
>>
>>         udelay(1000);
> 
> 
> 
> What is the point of setting TMIO_SD_CLKCTL_OFFEN
> when TMIO_SD_CLKCTL_SCLKEN is unset?
> 
> 
> Why isn't the code like this?
> 
> 
>         if (!mmc->clk_disable)
>                 tmp |= TMIO_SD_CLKCTL_SCLKEN;
>         else
>                 tmp &= ~TMIO_SD_CLKCTL_SCLKEN;
> 
>         /* Never use OFFEN because it interferes with 1.8 switching */
>         tmp &= ~TMIO_SD_CLKCTL_OFFEN;
> 
>         tmio_sd_writel(priv, tmp, TMIO_SD_CLKCTL);
> 

I think this could be done, but I'd have to re-run the entire bulk of
tests on all boards to see if nothing broke. I'd prefer to get this in
(if it doesn't break your system) and then add a patch on top.

> One more thing, you wrote
> 
>         if (!mmc->clk_disable)
>                 ...
>         else
>                 ...
> 
> in this patch.
> 
> 
> Then, soon you will rewrite it to
> 
>         if (mmc->clk_disable)
>                 ...
>         else
>                 ...
> 
> in another patch:
> 
> http://patchwork.ozlabs.org/patch/998542/

I know, I added the other one afterward, since I discovered another card
which had clock problems.

-- 
Best regards,
Marek Vasut