LinuxLists.cc - [PATCH v2 1/2] mmc: sdhci-esdhc-imx: disable clocks before changing frequency

2018-07-12 08:08:56

Subject: [PATCH v2 1/2] 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 changing frequency for uSDHC
IP variants too.

Signed-off-by: Stefan Agner <[email protected]>
---
drivers/mmc/host/sdhci-esdhc-imx.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index 85fd5a8b0b6d..acacd8481473 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;
}

--
2.18.0

2018-07-12 08:09:03

by Stefan Agner

[permalink] [raw]

Subject: [PATCH v2 2/2] mmc: sdhci-esdhc-imx: fix indent

Fix indent. This also makes disable/enable clock blocks look
alike.

Signed-off-by: Stefan Agner <[email protected]>
---
drivers/mmc/host/sdhci-esdhc-imx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
index acacd8481473..aa48f4b2541a 100644
--- a/drivers/mmc/host/sdhci-esdhc-imx.c
+++ b/drivers/mmc/host/sdhci-esdhc-imx.c
@@ -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

2018-07-12 08:46:49

by Aisheng Dong

[permalink] [raw]

Subject: RE: [PATCH v2 1/2] mmc: sdhci-esdhc-imx: disable clocks before changing frequency

> -----Original Message-----
> From: Stefan Agner [mailto:[email protected]]
> Sent: Thursday, July 12, 2018 4:07 PM
> To: [email protected]; [email protected]
> Cc: Fabio Estevam <[email protected]>; Bough Chen
> <[email protected]>; A.s. Dong <[email protected]>; linux-
> [email protected]; [email protected]; Stefan Agner
> <[email protected]>
> Subject: [PATCH v2 1/2] 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 changing frequency for uSDHC IP
> variants too.

Looks ok to me.
Acked-by: Dong Aisheng <[email protected]>

Regards
Dong Aisheng

>
> Signed-off-by: Stefan Agner <[email protected]>
> ---
> drivers/mmc/host/sdhci-esdhc-imx.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-
> esdhc-imx.c
> index 85fd5a8b0b6d..acacd8481473 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;
> }
>
> --
> 2.18.0

2018-07-12 08:47:11

by Aisheng Dong

[permalink] [raw]

Subject: RE: [PATCH v2 2/2] mmc: sdhci-esdhc-imx: fix indent

2018-07-12 12:53:48

by Adrian Hunter

[permalink] [raw]

Subject: Re: [PATCH v2 1/2] mmc: sdhci-esdhc-imx: disable clocks before changing frequency

On 12/07/18 11:07, 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 changing frequency for uSDHC
> IP variants too.
>
> Signed-off-by: Stefan Agner <[email protected]>

Acked-by: Adrian Hunter <[email protected]>

> ---
> drivers/mmc/host/sdhci-esdhc-imx.c | 12 ++++++------
> 1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 85fd5a8b0b6d..acacd8481473 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;
> }
>
>

2018-07-12 12:54:19

by Adrian Hunter

[permalink] [raw]

Subject: Re: [PATCH v2 2/2] mmc: sdhci-esdhc-imx: fix indent

On 12/07/18 11:07, Stefan Agner wrote:
> Fix indent. This also makes disable/enable clock blocks look
> alike.
>
> Signed-off-by: Stefan Agner <[email protected]>

Acked-by: Adrian Hunter <[email protected]>

> ---
> drivers/mmc/host/sdhci-esdhc-imx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index acacd8481473..aa48f4b2541a 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -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);
>

2018-07-16 10:12:28

by Ulf Hansson

[permalink] [raw]

Subject: Re: [PATCH v2 2/2] mmc: sdhci-esdhc-imx: fix indent

On 12 July 2018 at 10:07, Stefan Agner <[email protected]> wrote:
> Fix indent. This also makes disable/enable clock blocks look
> alike.
>
> Signed-off-by: Stefan Agner <[email protected]>

Thanks, applied for next!

Kind regards
Uffe

> ---
> drivers/mmc/host/sdhci-esdhc-imx.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index acacd8481473..aa48f4b2541a 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -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
>