2018-07-05 12:16:47

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

2018-07-05 13:11:10

by Ulf Hansson

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

On 5 July 2018 at 14:15, Stefan Agner <[email protected]> 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
> IP variants too. Also fix indent to make disable/enable clock look
> alike.
>
> Signed-off-by: Stefan Agner <[email protected]>

Thanks, applied for next!

Please tell if you want this for fixes and if I should add a stable tag.

Kind regards
Uffe

> ---
> 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
>

2018-07-05 14:27:53

by Stefan Agner

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

On 05.07.2018 15:09, Ulf Hansson wrote:
> On 5 July 2018 at 14:15, Stefan Agner <[email protected]> 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
>> IP variants too. Also fix indent to make disable/enable clock look
>> alike.
>>
>> Signed-off-by: Stefan Agner <[email protected]>
>
> Thanks, applied for next!
>
> Please tell if you want this for fixes and if I should add a stable tag.

I haven't seen any direct negative impact by that, so I don't think its
worth back-porting at this point.

--
Stefan

>
> Kind regards
> Uffe
>
>> ---
>> 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
>>