2018-07-05 11:40:58

by Stefan Agner

Subject: [PATCH] mmc: sdhci-esdhc-imx: disable clocks before changing frequency

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
IP variants too. Also fix indent to make disable/enable clock look
alike.

Signed-off-by: Stefan Agner <[email protected]>
---
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);
}

mdelay(1);
--
2.18.0

2018-07-11 15:40:31

by Adrian Hunter

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

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 <[email protected]>
> ---
> 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);
>

2018-07-11 15:45:46

by Ulf Hansson

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

On 11 July 2018 at 14:29, Adrian Hunter <[email protected]> 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 <[email protected]>
>> ---
>> 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