linux-kernel - Re: [RFC PATCH v3.1 18/27] mmc: sdhci-uhs2: add clock operations

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Message-ID: <20201201022711.GB43403@laputa>
Date:   Tue, 1 Dec 2020 11:27:11 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     ulf.hansson@...aro.org, linux-mmc@...r.kernel.org,
        linux-kernel@...r.kernel.org, ben.chuang@...esyslogic.com.tw,
        greg.tu@...esyslogic.com.tw
Subject: Re: [RFC PATCH v3.1 18/27] mmc: sdhci-uhs2: add clock operations

On Thu, Nov 26, 2020 at 10:17:59AM +0200, Adrian Hunter wrote:
> On 6/11/20 4:27 am, AKASHI Takahiro wrote:
> > This is a sdhci version of mmc's uhs2_[enable|disable]_clk operations.
> > 
> > Signed-off-by: Ben Chuang <ben.chuang@...esyslogic.com.tw>
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> > ---
> >  drivers/mmc/host/sdhci-uhs2.c | 41 +++++++++++++++++++++++++++++++++++
> >  1 file changed, 41 insertions(+)
> > 
> > diff --git a/drivers/mmc/host/sdhci-uhs2.c b/drivers/mmc/host/sdhci-uhs2.c
> > index 994dff967e85..55362ace1857 100644
> > --- a/drivers/mmc/host/sdhci-uhs2.c
> > +++ b/drivers/mmc/host/sdhci-uhs2.c
> > @@ -11,6 +11,7 @@
> >   */
> >  
> >  #include <linux/delay.h>
> > +#include <linux/ktime.h>
> >  #include <linux/module.h>
> >  
> >  #include "sdhci.h"
> > @@ -385,6 +386,42 @@ void sdhci_uhs2_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> >  	__sdhci_uhs2_set_ios(mmc, ios);
> >  }
> >  
> > +static void sdhci_uhs2_disable_clk(struct mmc_host *mmc)
> > +{
> > +        struct sdhci_host *host = mmc_priv(mmc);
> > +	u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > +
> > +	clk &= ~SDHCI_CLOCK_CARD_EN;
> > +	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > +}
> > +
> > +static void sdhci_uhs2_enable_clk(struct mmc_host *mmc)
> > +{
> > +        struct sdhci_host *host = mmc_priv(mmc);
> > +	u16 clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> > +	ktime_t timeout;
> > +
> > +	clk |= SDHCI_CLOCK_CARD_EN;
> > +	sdhci_writew(host, clk, SDHCI_CLOCK_CONTROL);
> > +
> > +	/* Wait max 20 ms */
> > +	timeout = ktime_add_ms(ktime_get(), 20);
> > +	while (1) {
> > +		bool timedout = ktime_after(ktime_get(), timeout);
> > +
> > +		clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL);
> 
> Can use read_poll_timeout(sdhci_readw,..., host, SDHCI_CLOCK_CONTROL)

Okay.

-Takahiro Akashi

> > +		if (clk & SDHCI_CLOCK_INT_STABLE)
> > +			break;
> > +		if (timedout) {
> > +			pr_err("%s: Internal clock never stabilised.\n",
> > +			       mmc_hostname(host->mmc));
> > +			sdhci_dumpregs(host);
> > +			return;
> > +		}
> > +		udelay(10);
> > +	}
> > +}
> > +
> >  /*****************************************************************************\
> >   *                                                                           *
> >   * Driver init/exit                                                          *
> > @@ -556,6 +593,10 @@ static int sdhci_uhs2_host_ops_init(struct sdhci_host *host)
> >  
> >  	if (!host->mmc_host_ops.uhs2_detect_init)
> >  		host->mmc_host_ops.uhs2_detect_init = sdhci_uhs2_do_detect_init;
> > +	if (!host->mmc_host_ops.uhs2_disable_clk)
> > +		host->mmc_host_ops.uhs2_disable_clk = sdhci_uhs2_disable_clk;
> > +	if (!host->mmc_host_ops.uhs2_enable_clk)
> > +		host->mmc_host_ops.uhs2_enable_clk = sdhci_uhs2_enable_clk;
> >  
> >  	return 0;
> >  }
> > 
>