linux-kernel - Re: [PATCH 1/2] mmc: sdhci-esdhc-imx: refactor clock loopback selection logic

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Message-ID: <6be8a114-7775-415d-a48f-751466cce44d@intel.com>
Date: Wed, 28 May 2025 13:34:29 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: <ziniu.wang_1@....com>, <haibo.chen@....com>, <ulf.hansson@...aro.org>,
	<linux-mmc@...r.kernel.org>
CC: <shawnguo@...nel.org>, <s.hauer@...gutronix.de>, <kernel@...gutronix.de>,
	<festevam@...il.com>, <imx@...ts.linux.dev>, <s32@....com>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/2] mmc: sdhci-esdhc-imx: refactor clock loopback
 selection logic

On 21/05/2025 05:55, ziniu.wang_1@....com wrote:
> From: Luke Wang <ziniu.wang_1@....com>
> 
> i.MX reference manual specifies that internal clock loopback should be
> used for SDR104/HS200/HS400 modes. Move ESDHC_MIX_CTRL_FBCLK_SEL
> configuration into the timing selection function to:
> 
> 1. Explicitly set internal loopback path for SDR104/HS200/HS400 modes
> 2. Avoid redundant bit manipulation across multiple functions
> 
> Preserve ESDHC_MIX_CTRL_FBCLK_SEL during system resume for SDIO devices
> with MMC_PM_KEEP_POWER and MMC_PM_WAKE_SDIO_IRQ flag, as the controller
> might lose register state during suspend while skipping card
> re-initialization.
> 
> Signed-off-by: Luke Wang <ziniu.wang_1@....com>

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

> ---
>  drivers/mmc/host/sdhci-esdhc-imx.c | 27 ++++++++++++++-------------
>  1 file changed, 14 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc-imx.c b/drivers/mmc/host/sdhci-esdhc-imx.c
> index 7611682f10c3..c448a53530a5 100644
> --- a/drivers/mmc/host/sdhci-esdhc-imx.c
> +++ b/drivers/mmc/host/sdhci-esdhc-imx.c
> @@ -728,23 +728,17 @@ static void esdhc_writew_le(struct sdhci_host *host, u16 val, int reg)
>  		writel(new_val, host->ioaddr + ESDHC_VENDOR_SPEC);
>  		if (imx_data->socdata->flags & ESDHC_FLAG_STD_TUNING) {
>  			u32 v = readl(host->ioaddr + SDHCI_AUTO_CMD_STATUS);
> -			u32 m = readl(host->ioaddr + ESDHC_MIX_CTRL);
> -			if (val & SDHCI_CTRL_TUNED_CLK) {
> +			if (val & SDHCI_CTRL_TUNED_CLK)
>  				v |= ESDHC_MIX_CTRL_SMPCLK_SEL;
> -			} else {
> +			else
>  				v &= ~ESDHC_MIX_CTRL_SMPCLK_SEL;
> -				m &= ~ESDHC_MIX_CTRL_FBCLK_SEL;
> -			}
>  
> -			if (val & SDHCI_CTRL_EXEC_TUNING) {
> +			if (val & SDHCI_CTRL_EXEC_TUNING)
>  				v |= ESDHC_MIX_CTRL_EXE_TUNE;
> -				m |= ESDHC_MIX_CTRL_FBCLK_SEL;
> -			} else {
> +			else
>  				v &= ~ESDHC_MIX_CTRL_EXE_TUNE;
> -			}
>  
>  			writel(v, host->ioaddr + SDHCI_AUTO_CMD_STATUS);
> -			writel(m, host->ioaddr + ESDHC_MIX_CTRL);
>  		}
>  		return;
>  	case SDHCI_TRANSFER_MODE:
> @@ -1082,7 +1076,6 @@ static void esdhc_reset_tuning(struct sdhci_host *host)
>  		ctrl &= ~ESDHC_MIX_CTRL_AUTO_TUNE_EN;
>  		if (imx_data->socdata->flags & ESDHC_FLAG_MAN_TUNING) {
>  			ctrl &= ~ESDHC_MIX_CTRL_SMPCLK_SEL;
> -			ctrl &= ~ESDHC_MIX_CTRL_FBCLK_SEL;
>  			writel(ctrl, host->ioaddr + ESDHC_MIX_CTRL);
>  			writel(0, host->ioaddr + ESDHC_TUNE_CTRL_STATUS);
>  		} else if (imx_data->socdata->flags & ESDHC_FLAG_STD_TUNING) {
> @@ -1177,8 +1170,7 @@ static void esdhc_prepare_tuning(struct sdhci_host *host, u32 val)
>  		"warning! RESET_ALL never complete before sending tuning command\n");
>  
>  	reg = readl(host->ioaddr + ESDHC_MIX_CTRL);
> -	reg |= ESDHC_MIX_CTRL_EXE_TUNE | ESDHC_MIX_CTRL_SMPCLK_SEL |
> -			ESDHC_MIX_CTRL_FBCLK_SEL;
> +	reg |= ESDHC_MIX_CTRL_EXE_TUNE | ESDHC_MIX_CTRL_SMPCLK_SEL;
>  	writel(reg, host->ioaddr + ESDHC_MIX_CTRL);
>  	writel(FIELD_PREP(ESDHC_TUNE_CTRL_STATUS_DLY_CELL_SET_PRE_MASK, val),
>  	       host->ioaddr + ESDHC_TUNE_CTRL_STATUS);
> @@ -1432,6 +1424,15 @@ static void esdhc_set_uhs_signaling(struct sdhci_host *host, unsigned timing)
>  		break;
>  	}
>  
> +	if (timing == MMC_TIMING_UHS_SDR104 ||
> +	    timing == MMC_TIMING_MMC_HS200 ||
> +	    timing == MMC_TIMING_MMC_HS400)
> +		m |= ESDHC_MIX_CTRL_FBCLK_SEL;
> +	else
> +		m &= ~ESDHC_MIX_CTRL_FBCLK_SEL;
> +
> +	writel(m, host->ioaddr + ESDHC_MIX_CTRL);
> +
>  	esdhc_change_pinstate(host, timing);
>  }
>