Re: [PATCH v2] mmc: litex_mmc: Set mandatory idle clocks before CMD0

[Gabriel L. Somlo]

Hi,

Thanks for the patch!

On Fri, Apr 24, 2026 at 09:36:14AM +0800, Inochi Amaoto wrote:
> The litex_mmc driver assumes the card is already probed in the BIOS
> and skip the phy initialization. This will cause the command fail
> like the following when the old card is unplugged and then insert
> a new card:
> 
> [   62.923593] litex-mmc f0004000.mmc: Command (cmd 8) error, status -110
> [   62.949717] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> [   62.976606] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> [   63.002516] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> [   63.028442] litex-mmc f0004000.mmc: Command (cmd 55) error, status -110
> 
> Add required clock settings and initialization for the CMD 0, so it can
> probe the new card.
> 
> Fixes: 92e099104729 ("mmc: Add driver for LiteX's LiteSDCard interface")
> Signed-off-by: Inochi Amaoto <inochiama@xxxxxxxxx>
> ---
> Change from v1:
> - https://lore.kernel.org/linux-mmc/20260421025052.755471-1-inochiama@xxxxxxxxx/
> 1. use fsleep to replace udelay
> ---
>  drivers/mmc/host/litex_mmc.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/mmc/host/litex_mmc.c b/drivers/mmc/host/litex_mmc.c
> index d2f19c2dc673..ac0b47604c02 100644
> --- a/drivers/mmc/host/litex_mmc.c
> +++ b/drivers/mmc/host/litex_mmc.c
> @@ -68,6 +68,9 @@
>  #define SD_SLEEP_US       5
>  #define SD_TIMEOUT_US 20000
> 
> +#define SD_INIT_DELAY_US  1000
> +#define SD_INIT_CLK_HZ    400000
> +
>  #define SDIRQ_CARD_DETECT    1
>  #define SDIRQ_SD_TO_MEM_DONE 2
>  #define SDIRQ_MEM_TO_SD_DONE 4
> @@ -99,6 +102,8 @@ struct litex_mmc_host {
>  	bool app_cmd;
>  };
> 
> +static void litex_mmc_setclk(struct litex_mmc_host *host, unsigned int freq);
> +

Instead of the forward reference, can you simply move the entire
`litex_mmc_setclk` function definition to this location in the file?
(i.e., add a separate, "cosmetic" patch simply cut'n'pasting the
function body from one place to another, with a commit blurb stating
that it's in preparation for the idle-clock fix, and that it contains
only cosmetic, no functional changes)?

The idle-clock fix patch can then contain nothing but the
"#define SD_INIT_*" lines and the hunk below:

>  static int litex_mmc_sdcard_wait_done(void __iomem *reg, struct device *dev)
>  {
>  	u8 evt;
> @@ -128,6 +133,12 @@ static int litex_mmc_send_cmd(struct litex_mmc_host *host,
>  	int ret;
>  	u8 evt;
> 
> +	if (cmd == MMC_GO_IDLE_STATE) {
> +		litex_mmc_setclk(host, SD_INIT_CLK_HZ);
> +		litex_write8(host->sdphy + LITEX_PHY_INITIALIZE, 1);
> +		fsleep(SD_INIT_DELAY_US);
> +	}
> +
>  	litex_write32(host->sdcore + LITEX_CORE_CMDARG, arg);
>  	litex_write32(host->sdcore + LITEX_CORE_CMDCMD,
>  		      cmd << 8 | transfer << 5 | response_len);

Thanks much,
--Gabriel