RE: [PATCH v3 1/2] mmc: host: sdhci-esdhc-imx: implement emmc hardware reset

[Bough Chen]

> -----Original Message-----
> From: Josua Mayer <josua@xxxxxxxxxxxxx>
> Sent: 2024年11月1日 19:42
> To: Adrian Hunter <adrian.hunter@xxxxxxxxx>; Bough Chen
> <haibo.chen@xxxxxxx>; Ulf Hansson <ulf.hansson@xxxxxxxxxx>; Shawn Guo
> <shawnguo@xxxxxxxxxx>; Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>;
> Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>; Fabio Estevam
> <festevam@xxxxxxxxx>
> Cc: Mikhail Anikin <mikhail.anikin@xxxxxxxxxxxxx>; Jon Nettleton
> <jon@xxxxxxxxxxxxx>; yazan.shhady <yazan.shhady@xxxxxxxxxxxxx>; Rabeeh
> Khoury <rabeeh@xxxxxxxxxxxxx>; imx@xxxxxxxxxxxxxxx;
> linux-mmc@xxxxxxxxxxxxxxx; dl-S32 <S32@xxxxxxx>;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Josua
> Mayer <josua@xxxxxxxxxxxxx>
> Subject: [PATCH v3 1/2] 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.
> 
> Implement the hw_reset function in sdhci_ops asserting reset for at least 1us
> and waiting at least 200us after deassertion.
> Lower bounds are based on:
> JEDEC Standard No. 84-B51, 6.15.10 H/W Reset Operation, page 159.
> Upper bounds are chosen allowing flexibility to the scheduler.
> 
> 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
> - sdhc node has cap-mmc-hw-reset
> - pinmux set for EMMC0_RESET_B
> - Linux v5.15

Reviewed-by: Haibo Chen <haibo.chen@xxxxxxx>

Best Regards
Haibo Chen
> 
> Signed-off-by: Josua Mayer <josua@xxxxxxxxxxxxx>
> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c
> b/drivers/mmc/host/sdhci-esdhc-imx.c
> index
> 8f0bc6dca2b0402fd2a0695903cf261a5b4e19dc..f106e291c276d0c8063e9ac59
> a126acf5e9e239e 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -31,6 +31,7 @@
>  #include "cqhci.h"
> 
>  #define ESDHC_SYS_CTRL_DTOCV_MASK	0x0f
> +#define ESDHC_SYS_CTRL_IPP_RST_N	BIT(23)
>  #define	ESDHC_CTRL_D3CD			0x08
>  #define ESDHC_BURST_LEN_EN_INCR		(1 << 27)
>  /* VENDOR SPEC register */
> @@ -1402,6 +1403,17 @@ 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_SYSTEM_CONTROL);
> +	/* eMMC spec requires minimum 1us, here delay between 1-10us */
> +	usleep_range(1, 10);
> +	esdhc_clrset_le(host, ESDHC_SYS_CTRL_IPP_RST_N,
> +			ESDHC_SYS_CTRL_IPP_RST_N, ESDHC_SYSTEM_CONTROL);
> +	/* eMMC spec requires minimum 200us, here delay between 200-300us */
> +	usleep_range(200, 300);
> +}
> +
>  static struct sdhci_ops sdhci_esdhc_ops = {
>  	.read_l = esdhc_readl_le,
>  	.read_w = esdhc_readw_le,
> @@ -1420,6 +1432,7 @@ 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 = {
> 
> --
> 2.43.0