linux-kernel - Re: [PATCH v2 1/2] mmc: sdhci: Add PLL Enable support to internal clock setup

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Date:   Wed, 7 Aug 2019 12:05:59 +0300
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     "Michael K. Johnson" <johnsonm@...lj.org>, ulf.hansson@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-mmc@...r.kernel.org,
        Ben Chuang <ben.chuang@...esyslogic.com.tw>
Subject: Re: [PATCH v2 1/2] mmc: sdhci: Add PLL Enable support to internal
 clock setup

On 26/07/19 5:07 AM, Michael K. Johnson wrote:
> The GL9750 and GL9755 chipsets, and possibly others, require PLL Enable
> setup as part of the internal clock setup as described in 3.2.1 Internal
> Clock Setup Sequence of SD Host Controller Simplified Specification
> Version 4.20.  This changes the timeouts to the new specification of
> 150ms for each step and is documented as safe for "prior versions which
> do not support PLL Enable."
> 
> Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
> Co-developed-by: Michael K Johnson <johnsonm@...lj.org>
> Signed-off-by: Michael K Johnson <johnsonm@...lj.org>
> 
> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
> index 59acf8e3331e..14957578bf2e 100644
> --- a/drivers/mmc/host/sdhci.c
> +++ b/drivers/mmc/host/sdhci.c
> @@ -1636,8 +1636,8 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)
>  	clk |= SDHCI_CLOCK_INT_EN;
>  	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
>  
> -	/* Wait max 20 ms */
> -	timeout = ktime_add_ms(ktime_get(), 20);
> +	/* Wait max 150 ms */
> +	timeout = ktime_add_ms(ktime_get(), 150);
>  	while (1) {
>  		bool timedout = ktime_after(ktime_get(), timeout);
>  
> @@ -1650,7 +1650,28 @@ void sdhci_enable_clk(struct sdhci_host *host, u16 clk)
>  			sdhci_dumpregs(host);
>  			return;
>  		}
> -		udelay(10);
> +		usleep_range(10,15);

There is still one place that calls ->set_clock() under spinlock, so that
needs to stay udelay(10) for now.

> +	}
> +

PLL Enable is only valid from v4.1 i.e.

	if (host->version >= SDHCI_SPEC_410 && host->v4_mode)


> +	clk |= SDHCI_CLOCK_PLL_EN;
> +	clk &= ~SDHCI_CLOCK_INT_STABLE;
> +	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> +
> +	/* Wait max 150 ms */
> +	timeout = ktime_add_ms(ktime_get(), 150);
> +	while (1) {
> +		bool timedout = ktime_after(ktime_get(), timeout);
> +
> +		clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> +		if (clk & SDHCI_CLOCK_INT_STABLE)
> +			break;
> +		if (timedout) {
> +			pr_err("%s: PLL clock never stabilised.\n",
> +			       mmc_hostname(host->mmc));
> +			sdhci_dumpregs(host);
> +			return;
> +		}
> +		usleep_range(10,15);
>  	}
>  
>  	clk |= SDHCI_CLOCK_CARD_EN;
> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
> index 199712e7adbb..72601a4d2e95 100644
> --- a/drivers/mmc/host/sdhci.h
> +++ b/drivers/mmc/host/sdhci.h
> @@ -114,6 +114,7 @@
>  #define  SDHCI_DIV_HI_MASK	0x300
>  #define  SDHCI_PROG_CLOCK_MODE	0x0020
>  #define  SDHCI_CLOCK_CARD_EN	0x0004
> +#define  SDHCI_CLOCK_PLL_EN	0x0008
>  #define  SDHCI_CLOCK_INT_STABLE	0x0002
>  #define  SDHCI_CLOCK_INT_EN	0x0001
>  
>