RE: [PATCH] mmc: host: sdhci-esdhc-imx: implement emmc hardware reset

[Peng Fan]

> Subject: [PATCH] mmc: host: sdhci-esdhc-imx: implement emmc
> hardware reset
> 
> NXP ESDHC supports control of native emmc reset signal when pinmux
> is set accordingly, using uSDHCx_SYS_CTRL register IPP_RST_N bit.
> Documentation is available in NXP i.MX6Q Reference Manual.

But this relies on the PAD been configured as RESET, should this
flow being default enabled whether the PAD is configured as RESET or
not?

> 
> Implement the hw_reset function in sdhci_ops asserting reset for at
> least 10us and waiting an extra 300us after deassertion.
> These particular delays were inspired by sunxi-mmc hw_reset function.
> 
> Tested on SolidRun i.MX8DXL SoM with a scope, and confirmed that
> eMMC is still accessible after boot. eMMC extcsd has
> RST_N_FUNCTION=0x01, i.e.
> reset input enabled, Linux v5.15.
> 
> Signed-off-by: Josua Mayer <josua@xxxxxxxxxxxxx>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> b/drivers/mmc/host/sdhci-esdhc-imx.c
> index
> 8f0bc6dca2b0402fd2a0695903cf261a5b4e19dc..ebcfa427cca6cc2791
> a1701a3515ef6515779aa4 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -33,6 +33,8 @@
>  #define ESDHC_SYS_CTRL_DTOCV_MASK	0x0f
>  #define	ESDHC_CTRL_D3CD			0x08
>  #define ESDHC_BURST_LEN_EN_INCR		(1 << 27)
> +#define ESDHC_SYS_CTRL			0x2c
> +#define ESDHC_SYS_CTRL_IPP_RST_N	BIT(23)
>  /* VENDOR SPEC register */
>  #define ESDHC_VENDOR_SPEC		0xc0
>  #define  ESDHC_VENDOR_SPEC_SDIO_QUIRK	(1 << 1)
> @@ -1402,6 +1404,15 @@ static u32 esdhc_cqhci_irq(struct
> sdhci_host *host, u32 intmask)
>  	return 0;
>  }
> 
> +static void esdhc_hw_reset(struct sdhci_host *host) {
> +	esdhc_clrset_le(host, ESDHC_SYS_CTRL_IPP_RST_N, 0,
> ESDHC_SYS_CTRL);
> +	udelay(10);
> +	esdhc_clrset_le(host, ESDHC_SYS_CTRL_IPP_RST_N,
> +			ESDHC_SYS_CTRL_IPP_RST_N,
> ESDHC_SYS_CTRL);
> +	udelay(300);

Please add a comment on why 10us or 300us? This is board
related or soc related or card related?

Thanks,
Peng.

> +}
> +
>  static struct sdhci_ops sdhci_esdhc_ops = {
>  	.read_l = esdhc_readl_le,
>  	.read_w = esdhc_readw_le,
> @@ -1420,6 +1431,7 @@ static struct sdhci_ops sdhci_esdhc_ops = {
>  	.reset = esdhc_reset,
>  	.irq = esdhc_cqhci_irq,
>  	.dump_vendor_regs = esdhc_dump_debug_regs,
> +	.hw_reset = esdhc_hw_reset,
>  };
> 
>  static const struct sdhci_pltfm_data sdhci_esdhc_imx_pdata = {
> 
> ---
> base-commit: 9852d85ec9d492ebef56dc5f229416c925758edc
> change-id: 20241027-imx-emmc-reset-7127d311174c
> 
> Best regards,
> --
> Josua Mayer <josua@xxxxxxxxxxxxx>
>