[PATCH v3 1/7] mmc: sdhci-of-k1: enable essential clock infrastructure for SD operation

[Adrian Hunter]

On 16/03/2026 16:03, Iker Pedrosa wrote:
> Ensure SD card pins receive clock signals by enabling pad clock
> generation and overriding automatic clock gating. Required for all SD
> operation modes.
> 
> The SDHC_GEN_PAD_CLK_ON setting in LEGACY_CTRL_REG is safe for both SD
> and eMMC operation as both protocols use the same physical MMC interface
> pins and require proper clock signal generation at the hardware level
> for signal integrity and timing.
> 
> Additional SD-specific clock overrides (SDHC_OVRRD_CLK_OEN and
> SDHC_FORCE_CLK_ON) are conditionally applied only for SD-only
> controllers to handle removable card scenarios.
> 
> Tested-by: Anand Moon <linux.amoon at gmail.com>
> Signed-off-by: Iker Pedrosa <ikerpedrosam at gmail.com>

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

> ---
>  drivers/mmc/host/sdhci-of-k1.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-of-k1.c b/drivers/mmc/host/sdhci-of-k1.c
> index 455656f9842df90c7a94a290aeec22157b378fc1..0dd06fc19b8574ae1b00f7e5d09b7d4c87d06770 100644
> --- a/drivers/mmc/host/sdhci-of-k1.c
> +++ b/drivers/mmc/host/sdhci-of-k1.c
> @@ -21,6 +21,13 @@
>  #include "sdhci.h"
>  #include "sdhci-pltfm.h"
>  
> +#define SPACEMIT_SDHC_OP_EXT_REG	0x108
> +#define  SDHC_OVRRD_CLK_OEN		BIT(11)
> +#define  SDHC_FORCE_CLK_ON		BIT(12)
> +
> +#define SPACEMIT_SDHC_LEGACY_CTRL_REG	0x10C
> +#define  SDHC_GEN_PAD_CLK_ON		BIT(6)
> +
>  #define SPACEMIT_SDHC_MMC_CTRL_REG	0x114
>  #define  SDHC_MISC_INT_EN		BIT(1)
>  #define  SDHC_MISC_INT			BIT(2)
> @@ -101,6 +108,12 @@ static void spacemit_sdhci_reset(struct sdhci_host *host, u8 mask)
>  
>  	if (!(host->mmc->caps2 & MMC_CAP2_NO_MMC))
>  		spacemit_sdhci_setbits(host, SDHC_MMC_CARD_MODE, SPACEMIT_SDHC_MMC_CTRL_REG);
> +
> +	spacemit_sdhci_setbits(host, SDHC_GEN_PAD_CLK_ON, SPACEMIT_SDHC_LEGACY_CTRL_REG);
> +
> +	if (host->mmc->caps2 & MMC_CAP2_NO_MMC)
> +		spacemit_sdhci_setbits(host, SDHC_OVRRD_CLK_OEN | SDHC_FORCE_CLK_ON,
> +				       SPACEMIT_SDHC_OP_EXT_REG);
>  }
>  
>  static void spacemit_sdhci_set_uhs_signaling(struct sdhci_host *host, unsigned int timing)
>