[PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Erick Shepherd]

Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
the SD card clock parameters only after first disabling the external card
clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
SD controllers which otherwise breaks voltage switching with a specific
Swissbit SD card.

Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
Signed-off-by: Brad Mouring <brad.mouring@ni.com>
Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>
---
 drivers/mmc/host/sdhci.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
index f4a7733a8ad2..5f91b44891f9 100644
--- a/drivers/mmc/host/sdhci.c
+++ b/drivers/mmc/host/sdhci.c
@@ -2065,10 +2065,15 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
 
 	host->mmc->actual_clock = 0;
 
-	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
+	clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+	if (clk & SDHCI_CLOCK_CARD_EN)
+		sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN,
+			SDHCI_CLOCK_CONTROL);
 
-	if (clock == 0)
+	if (clock == 0) {
+		sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
 		return;
+	}
 
 	clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
 	sdhci_enable_clk(host, clk);
-- 
2.43.0

Re: [PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Adrian Hunter]

On 11/02/25 23:46, Erick Shepherd wrote:
> Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
> the SD card clock parameters only after first disabling the external card
> clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
> SD controllers which otherwise breaks voltage switching with a specific
> Swissbit SD card.
> 
> Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
> Signed-off-by: Brad Mouring <brad.mouring@ni.com>
> Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>

Acked-by: Adrian Hunter <adrian.hunter@intel.com>

> ---
>  drivers/mmc/host/sdhci.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index f4a7733a8ad2..5f91b44891f9 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2065,10 +2065,15 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>  
>  	host->mmc->actual_clock = 0;
>  
> -	sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> +	clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +	if (clk & SDHCI_CLOCK_CARD_EN)
> +		sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN,
> +			SDHCI_CLOCK_CONTROL);
>  
> -	if (clock == 0)
> +	if (clock == 0) {
> +		sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>  		return;
> +	}
>  
>  	clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
>  	sdhci_enable_clk(host, clk);

Re: [PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Ulf Hansson]

On Tue, 11 Feb 2025 at 22:47, Erick Shepherd <erick.shepherd@ni.com> wrote:
>
> Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
> the SD card clock parameters only after first disabling the external card
> clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
> SD controllers which otherwise breaks voltage switching with a specific
> Swissbit SD card.
>
> Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
> Signed-off-by: Brad Mouring <brad.mouring@ni.com>
> Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/sdhci.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index f4a7733a8ad2..5f91b44891f9 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2065,10 +2065,15 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>
>         host->mmc->actual_clock = 0;
>
> -       sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> +       clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +       if (clk & SDHCI_CLOCK_CARD_EN)
> +               sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN,
> +                       SDHCI_CLOCK_CONTROL);
>
> -       if (clock == 0)
> +       if (clock == 0) {
> +               sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>                 return;
> +       }
>
>         clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
>         sdhci_enable_clk(host, clk);
> --
> 2.43.0
>

Re: [PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Jonathan Liu]

Hi Erick,

On Tue, 11 Feb 2025 at 15:46, Erick Shepherd <erick.shepherd@ni.com> wrote:
>
> Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
> the SD card clock parameters only after first disabling the external card
> clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
> SD controllers which otherwise breaks voltage switching with a specific
> Swissbit SD card.
>
> Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
> Signed-off-by: Brad Mouring <brad.mouring@ni.com>
> Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>
> ---
>  drivers/mmc/host/sdhci.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index f4a7733a8ad2..5f91b44891f9 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -2065,10 +2065,15 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>
>         host->mmc->actual_clock = 0;
>
> -       sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
> +       clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +       if (clk & SDHCI_CLOCK_CARD_EN)
> +               sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN,
> +                       SDHCI_CLOCK_CONTROL);
>
> -       if (clock == 0)
> +       if (clock == 0) {
> +               sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>                 return;
> +       }
>
>         clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
>         sdhci_enable_clk(host, clk);
> --
> 2.43.0

This commit is causing eMMC to sometimes fail to detect on my RK3399
ARM64 board after updating from v5.10.237 to v5.10.238.
Any ideas?

Regards,
Jonathan

Re: [PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Adrian Hunter]

On 19/06/2025 06:29, Jonathan Liu wrote:
> Hi Erick,
> 
> On Tue, 11 Feb 2025 at 15:46, Erick Shepherd <erick.shepherd@ni.com> wrote:
>>
>> Per the SD Host Controller Simplified Specification v4.20 §3.2.3, change
>> the SD card clock parameters only after first disabling the external card
>> clock. Doing this fixes a spurious clock pulse on Baytrail and Apollo Lake
>> SD controllers which otherwise breaks voltage switching with a specific
>> Swissbit SD card.
>>
>> Signed-off-by: Kyle Roeschley <kyle.roeschley@ni.com>
>> Signed-off-by: Brad Mouring <brad.mouring@ni.com>
>> Signed-off-by: Erick Shepherd <erick.shepherd@ni.com>
>> ---
>>  drivers/mmc/host/sdhci.c | 9 +++++++--
>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>> index f4a7733a8ad2..5f91b44891f9 100644
>> --- a/drivers/mmc/host/sdhci.c
>> +++ b/drivers/mmc/host/sdhci.c
>> @@ -2065,10 +2065,15 @@ void sdhci_set_clock(struct sdhci_host *host, unsigned int clock)
>>
>>         host->mmc->actual_clock = 0;
>>
>> -       sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>> +       clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
>> +       if (clk & SDHCI_CLOCK_CARD_EN)
>> +               sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN,
>> +                       SDHCI_CLOCK_CONTROL);
>>
>> -       if (clock == 0)
>> +       if (clock == 0) {
>> +               sdhci_writew(host, 0, SDHCI_CLOCK_CONTROL);
>>                 return;
>> +       }
>>
>>         clk = sdhci_calc_clk(host, clock, &host->mmc->actual_clock);
>>         sdhci_enable_clk(host, clk);
>> --
>> 2.43.0
> 
> This commit is causing eMMC to sometimes fail to detect on my RK3399
> ARM64 board after updating from v5.10.237 to v5.10.238.
> Any ideas?

Looks like this patch will get reverted.

After that, would something like the following work instead?

diff --git a/drivers/mmc/host/sdhci-pci-core.c b/drivers/mmc/host/sdhci-pci-core.c
index dd084c8750f9..ad95218fe3b3 100644
--- a/drivers/mmc/host/sdhci-pci-core.c
+++ b/drivers/mmc/host/sdhci-pci-core.c
@@ -679,8 +679,19 @@ static int intel_start_signal_voltage_switch(struct mmc_host *mmc,
 	return 0;
 }
 
+static void sdhci_intel_set_clock(struct sdhci_host *host, unsigned int clock)
+{
+	u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
+
+	/* Stop card clock separately to avoid glitches on clock line */
+	if (clk & SDHCI_CLOCK_CARD_EN)
+		sdhci_writew(host, clk & ~SDHCI_CLOCK_CARD_EN, SDHCI_CLOCK_CONTROL);
+
+	sdhci_set_clock(host, clock);
+}
+
 static const struct sdhci_ops sdhci_intel_byt_ops = {
-	.set_clock		= sdhci_set_clock,
+	.set_clock		= sdhci_intel_set_clock,
 	.set_power		= sdhci_intel_set_power,
 	.enable_dma		= sdhci_pci_enable_dma,
 	.set_bus_width		= sdhci_set_bus_width,
@@ -690,7 +701,7 @@ static const struct sdhci_ops sdhci_intel_byt_ops = {
 };
 
 static const struct sdhci_ops sdhci_intel_glk_ops = {
-	.set_clock		= sdhci_set_clock,
+	.set_clock		= sdhci_intel_set_clock,
 	.set_power		= sdhci_intel_set_power,
 	.enable_dma		= sdhci_pci_enable_dma,
 	.set_bus_width		= sdhci_set_bus_width,

Re: [PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Erick Shepherd]

Hi Adrian,

I believe this fix would work since it looks like it keeps the
functionality of the previous change but only for intel SD
controllers. I also tested your proposed change on one of our devices
with a Baytrail SD controller and a Swissbit SD card and did not run
into any issues.

Regards,
Erick

Re: [PATCH] mmc: sdhci: Disable SD card clock before changing parameters

[Adrian Hunter]

On 23/07/2025 00:29, Erick Shepherd wrote:
> Hi Adrian,
> 
> I believe this fix would work since it looks like it keeps the
> functionality of the previous change but only for intel SD
> controllers. I also tested your proposed change on one of our devices
> with a Baytrail SD controller and a Swissbit SD card and did not run
> into any issues.

If you are OK with it, please submit it as a patch