linux-kernel - Re: [PATCH] mmc: sdhci-esdhc-imx: disable clocks before changing frequency

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Date:   Wed, 11 Jul 2018 15:04:05 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>,
        Stefan Agner <stefan@...er.ch>
Cc:     Fabio Estevam <fabio.estevam@....com>,
        Haibo Chen <haibo.chen@....com>,
        Aisheng Dong <aisheng.dong@....com>,
        "linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mmc: sdhci-esdhc-imx: disable clocks before changing frequency

On 11 July 2018 at 14:29, Adrian Hunter <adrian.hunter@...el.com> wrote:
> On 05/07/18 14:39, Stefan Agner wrote:
>> In the uSDHC case (e.g. i.MX 6) clocks only get disabled if frequency
>> is set to 0. However, it could be that the stack asks for a frequency
>> change while clocks are on. In that case the function clears the
>> divider registers (by clearing ESDHC_CLOCK_MASK) while the clock is
>> enabled! This causes a short period of time where the clock is
>> undivided (on a i.MX 6DL a clock of 196MHz has been measured).
>>
>> For older IP variants the driver disables clock by clearing some bits
>> in ESDHC_SYSTEM_CONTROL.
>>
>> Make sure to disable card clock before chainging frequency for uSDHC
>
> chainging -> changing
>
>> IP variants too. Also fix indent to make disable/enable clock look
>> alike.
>>
>> Signed-off-by: Stefan Agner <stefan@...er.ch>
>> ---
>>  drivers/mmc/host/sdhci-esdhc-imx.c | 14 +++++++-------
>>  1 file changed, 7 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
>> index 85fd5a8b0b6d..aa48f4b2541a 100644
>> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
>> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
>> @@ -708,14 +708,14 @@ static inline void esdhc_pltfm_set_clock(struct sdhci_host *host,
>>       int div = 1;
>>       u32 temp, val;
>>
>> +     if (esdhc_is_usdhc(imx_data)) {
>> +             val = readl(host->ioaddr + ESDHC_VENDOR_SPEC);
>> +             writel(val & ~ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
>> +                     host->ioaddr + ESDHC_VENDOR_SPEC);
>> +     }
>> +
>>       if (clock == 0) {
>>               host->mmc->actual_clock = 0;
>> -
>> -             if (esdhc_is_usdhc(imx_data)) {
>> -                     val = readl(host->ioaddr + ESDHC_VENDOR_SPEC);
>> -                     writel(val & ~ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
>> -                                     host->ioaddr + ESDHC_VENDOR_SPEC);
>> -             }
>>               return;
>>       }
>>
>> @@ -761,7 +761,7 @@ static inline void esdhc_pltfm_set_clock(struct sdhci_host *host,
>>       if (esdhc_is_usdhc(imx_data)) {
>>               val = readl(host->ioaddr + ESDHC_VENDOR_SPEC);
>>               writel(val | ESDHC_VENDOR_SPEC_FRC_SDCLK_ON,
>> -             host->ioaddr + ESDHC_VENDOR_SPEC);
>> +                     host->ioaddr + ESDHC_VENDOR_SPEC);
>
> Ideally each patch does only 1 thing.  Please make white-space fix-up a
> separate patch.
>
>>       }
>>
>>       mdelay(1);
>>
>

It turned out that I had already applied this one. I am going to
re-base my next branch next week, so dropping the patch by then.

Until then, the patch is reverted.

Stefan, please send a new version addressing Adrian's comments.

Kind regards
Uffe