Re: [PATCH] mmc: sdhci-of-esdhc: make sure delay chain locked for HS400

[Adrian Hunter <adrian.hunter@intel.com>]

On 16/10/20 7:25 am, Yangbo Lu wrote:
> For eMMC HS400 mode initialization, the DLL reset is a required step
> if DLL is enabled to use previously, like in bootloader.
> This step has not been documented in reference manual, but the RM will
> be fixed sooner or later.
> 
> This patch is to add the step of DLL reset, and make sure delay chain
> locked for HS400.
> 
> Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>
> ---
>  drivers/mmc/host/sdhci-esdhc.h    |  2 ++
>  drivers/mmc/host/sdhci-of-esdhc.c | 24 ++++++++++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/mmc/host/sdhci-esdhc.h b/drivers/mmc/host/sdhci-esdhc.h
> index a30796e..6de02f0 100644
> --- a/drivers/mmc/host/sdhci-esdhc.h
> +++ b/drivers/mmc/host/sdhci-esdhc.h
> @@ -5,6 +5,7 @@
>   * Copyright (c) 2007 Freescale Semiconductor, Inc.
>   * Copyright (c) 2009 MontaVista Software, Inc.
>   * Copyright (c) 2010 Pengutronix e.K.
> + * Copyright 2020 NXP
>   *   Author: Wolfram Sang <kernel@pengutronix.de>
>   */
>  
> @@ -88,6 +89,7 @@
>  /* DLL Config 0 Register */
>  #define ESDHC_DLLCFG0			0x160
>  #define ESDHC_DLL_ENABLE		0x80000000
> +#define ESDHC_DLL_RESET			0x40000000
>  #define ESDHC_DLL_FREQ_SEL		0x08000000
>  
>  /* DLL Config 1 Register */
> diff --git a/drivers/mmc/host/sdhci-of-esdhc.c b/drivers/mmc/host/sdhci-of-esdhc.c
> index 0b45eff..a39ff86 100644
> --- a/drivers/mmc/host/sdhci-of-esdhc.c
> +++ b/drivers/mmc/host/sdhci-of-esdhc.c
> @@ -4,6 +4,7 @@
>   *
>   * Copyright (c) 2007, 2010, 2012 Freescale Semiconductor, Inc.
>   * Copyright (c) 2009 MontaVista Software, Inc.
> + * Copyright 2020 NXP
>   *
>   * Authors: Xiaobo Xie <X.Xie@freescale.com>
>   *	    Anton Vorontsov <avorontsov@ru.mvista.com>
> @@ -743,6 +744,29 @@ static void esdhc_of_set_clock(struct sdhci_host *host, unsigned int clock)
>  		if (host->mmc->actual_clock == MMC_HS200_MAX_DTR)
>  			temp |= ESDHC_DLL_FREQ_SEL;
>  		sdhci_writel(host, temp, ESDHC_DLLCFG0);
> +
> +		temp |= ESDHC_DLL_RESET;
> +		sdhci_writel(host, temp, ESDHC_DLLCFG0);
> +		udelay(1);
> +		temp &= ~ESDHC_DLL_RESET;
> +		sdhci_writel(host, temp, ESDHC_DLLCFG0);
> +
> +		/* Wait max 20 ms */
> +		timeout = ktime_add_ms(ktime_get(), 20);
> +		while (1) {
> +			bool timedout = ktime_after(ktime_get(), timeout);
> +
> +			if (sdhci_readl(host, ESDHC_DLLSTAT0) &
> +			    ESDHC_DLL_STS_SLV_LOCK)
> +				break;
> +			if (timedout) {
> +				pr_err("%s: timeout for delay chain lock.\n",
> +					mmc_hostname(host->mmc));
> +				break;
> +			}
> +			usleep_range(10, 20);
> +		}

It is possible now to do these loops using read_poll_timeout
e.g. something like this:

	if (read_poll_timeout(sdhci_readl, temp, temp & ESDHC_DLL_STS_SLV_LOCK,
			      10, 20000, false, host, ESDHC_DLLSTAT0))
		pr_err("%s: timeout for delay chain lock.\n",
		       mmc_hostname(host->mmc));



> +
>  		temp = sdhci_readl(host, ESDHC_TBCTL);
>  		sdhci_writel(host, temp | ESDHC_HS400_WNDW_ADJUST, ESDHC_TBCTL);
>  
>