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Date:   Thu, 17 Sep 2020 14:12:53 +0900
From:   AKASHI Takahiro <takahiro.akashi@linaro.org>
To:     Adrian Hunter <adrian.hunter@intel.com>
Cc:     Ben Chuang <benchuanggli@gmail.com>, ulf.hansson@linaro.org,
        linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org,
        ben.chuang@genesyslogic.com.tw, greg.tu@genesyslogic.com.tw
Subject: Re: [RFC PATCH V3 12/21] mmc: sdhci: UHS-II support, add hooks for
 additional operations
Message-ID: <20200917051253.GA3094018@laputa>
Mail-Followup-To: AKASHI Takahiro <takahiro.akashi@linaro.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Ben Chuang <benchuanggli@gmail.com>, ulf.hansson@linaro.org,
        linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org,
        ben.chuang@genesyslogic.com.tw, greg.tu@genesyslogic.com.tw
References: <20200710111054.29562-1-benchuanggli@gmail.com>
 <9fa17d60-a540-d0d8-7b2c-0016c3b5c532@intel.com>
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In-Reply-To: <9fa17d60-a540-d0d8-7b2c-0016c3b5c532@intel.com>
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Adrian, Ben,

Regarding _reset() function,

On Fri, Aug 21, 2020 at 05:08:32PM +0300, Adrian Hunter wrote:
> On 10/07/20 2:10 pm, Ben Chuang wrote:
> > From: Ben Chuang <ben.chuang@genesyslogic.com.tw>
> > 
> > In this commit, UHS-II related operations will be called via a function
> > pointer array, sdhci_uhs2_ops, in order to make UHS-II support as
> > a kernel module.
> > This array will be initialized only if CONFIG_MMC_SDHCI_UHS2 is enabled
> > and when the UHS-II module is loaded. Otherwise, all the functions
> > stay void.
> > 
> > Signed-off-by: Ben Chuang <ben.chuang@genesyslogic.com.tw>
> > Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
> > ---
> >  drivers/mmc/host/sdhci.c | 152 ++++++++++++++++++++++++++++++++++-----
> >  1 file changed, 136 insertions(+), 16 deletions(-)
> > 

  (snip)

> >  	if (host->ops->platform_send_init_74_clocks)
> >  		host->ops->platform_send_init_74_clocks(host, ios->power_mode);
> >  
> > @@ -2331,7 +2411,7 @@ void sdhci_set_ios(struct mmc_host *mmc, struct mmc_ios *ios)
> >  	}
> >  
> >  	if (host->version >= SDHCI_SPEC_300) {
> > -		u16 clk, ctrl_2;
> > +		u16 clk;
> >  
> >  		if (!host->preset_enabled) {
> >  			sdhci_writeb(host, ctrl, SDHCI_HOST_CONTROL);
> > @@ -3173,11 +3253,19 @@ static bool sdhci_request_done(struct sdhci_host *host)
> >  			/* This is to force an update */
> >  			host->ops->set_clock(host, host->clock);
> >  
> > -		/* Spec says we should do both at the same time, but Ricoh
> > -		   controllers do not like that. */
> > -		sdhci_do_reset(host, SDHCI_RESET_CMD);
> > -		sdhci_do_reset(host, SDHCI_RESET_DATA);
> > -
> > +		if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > +		    host->mmc->flags & MMC_UHS2_INITIALIZED) {
> > +			if (sdhci_uhs2_ops.reset)
> > +				sdhci_uhs2_ops.reset(host,
> > +						     SDHCI_UHS2_SW_RESET_SD);
> > +		} else {
> > +			/*
> > +			 * Spec says we should do both at the same time, but
> > +			 * Ricoh controllers do not like that.
> > +			 */
> > +			sdhci_do_reset(host, SDHCI_RESET_CMD);
> > +			sdhci_do_reset(host, SDHCI_RESET_DATA);
> > +		}
> 
> Please look at using the existing ->reset() sdhci host op instead.

Well, the second argument to those reset functions is a bit-wise value
to different "reset" registers, SDHCI_SOFTWARE_RESET and SDHCI_UHS2_SW_RESET,
respectively.

This fact raises a couple of questions to me:

1) Does it make sense to merge two functionality into one, i.e.
   sdhci_do_reset(), which is set to call ->reset hook?

        -> Adrian

2) UHS2_SW_RESET_SD is done only at this place while there are many callsites
   of reset(RESET_CMD|RESET_DATA) in sdhci.c.
   Why does the current code work?

   I found, in sdhci-pci-gli.c,
   sdhci_gl9755_reset()
        /* reset sd-tran on UHS2 mode if need to reset cmd/data */
        if ((mask & SDHCI_RESET_CMD) | (mask & SDHCI_RESET_DATA))
                gl9755_uhs2_reset_sd_tran(host);

   Is this the trick to avoid the issue?
   (It looks redundant in terms of the hack above in sdhci_request_done()
   and even quite dirty to me. Moreover, no corresponding code for gl9750
   and gl9763.)

        -> Ben

3) (More or less SD specification issue)
   In UHS-II mode, do we have to call reset(SHCI_RESET_ALL) along with
   reset(UHS2_SW_RESET_FULL)?
   Under the current implementation, both will be called at the end.

        -> Adrian, Ben

4) (Not directly linked to UHS-II support)
  In some places, we see the sequence:
        sdhci_do_reset(host, SDHCI_RESET_CMD);
        sdhci_do_reset(host, SDHCI_RESET_DATA);
  while in other places,
        sdhci_do_reset(host, SDHCI_RESET_CMD | SDHCI_RESET_DATA);

  If the statement below is true,
> > -		/* Spec says we should do both at the same time, but Ricoh
> > -		   controllers do not like that. */
  the latter should be wrong.

        -> Adrian

-Takahiro Akashi


> >  		host->pending_reset = false;
> >  	}
> >  
> > @@ -3532,6 +3620,13 @@ static irqreturn_t sdhci_irq(int irq, void *dev_id)
> >  				  SDHCI_INT_BUS_POWER);
> >  		sdhci_writel(host, mask, SDHCI_INT_STATUS);
> >  
> > +		if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > +		    intmask & SDHCI_INT_ERROR &&
> > +		    host->mmc->flags & MMC_UHS2_SUPPORT) {
> > +			if (sdhci_uhs2_ops.irq)
> > +				sdhci_uhs2_ops.irq(host);
> > +		}
> > +
> 
> Please look at using the existing ->irq() sdhci host op instead
> 
> >  		if (intmask & (SDHCI_INT_CARD_INSERT | SDHCI_INT_CARD_REMOVE)) {
> >  			u32 present = sdhci_readl(host, SDHCI_PRESENT_STATE) &
> >  				      SDHCI_CARD_PRESENT;
> > @@ -4717,6 +4812,14 @@ int sdhci_setup_host(struct sdhci_host *host)
> >  		/* This may alter mmc->*_blk_* parameters */
> >  		sdhci_allocate_bounce_buffer(host);
> >  
> > +	if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > +	    host->version >= SDHCI_SPEC_400 &&
> > +	    sdhci_uhs2_ops.add_host) {
> > +		ret = sdhci_uhs2_ops.add_host(host, host->caps1);
> > +		if (ret)
> > +			goto unreg;
> > +	}
> > +
> 
> I think you should look at creating uhs2_add_host() instead
> 
> >  	return 0;
> >  
> >  unreg:
> > @@ -4738,6 +4841,8 @@ void sdhci_cleanup_host(struct sdhci_host *host)
> >  {
> >  	struct mmc_host *mmc = host->mmc;
> >  
> > +	/* FIXME: Do we have to do some cleanup for UHS2 here? */
> > +
> >  	if (!IS_ERR(mmc->supply.vqmmc))
> >  		regulator_disable(mmc->supply.vqmmc);
> >  
> > @@ -4766,6 +4871,14 @@ int __sdhci_add_host(struct sdhci_host *host)
> >  		mmc->cqe_ops = NULL;
> >  	}
> >  
> > +	if ((mmc->caps & MMC_CAP_UHS2) && !host->v4_mode) {
> > +		/* host doesn't want to enable UHS2 support */
> > +		mmc->caps &= ~MMC_CAP_UHS2;
> > +		mmc->flags &= ~MMC_UHS2_SUPPORT;
> > +
> > +		/* FIXME: Do we have to do some cleanup here? */
> > +	}
> > +
> >  	host->complete_wq = alloc_workqueue("sdhci", flags, 0);
> >  	if (!host->complete_wq)
> >  		return -ENOMEM;
> > @@ -4812,6 +4925,9 @@ int __sdhci_add_host(struct sdhci_host *host)
> >  unled:
> >  	sdhci_led_unregister(host);
> >  unirq:
> > +	if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > +	    sdhci_uhs2_ops.remove_host)
> > +		sdhci_uhs2_ops.remove_host(host, 0);
> >  	sdhci_do_reset(host, SDHCI_RESET_ALL);
> >  	sdhci_writel(host, 0, SDHCI_INT_ENABLE);
> >  	sdhci_writel(host, 0, SDHCI_SIGNAL_ENABLE);
> > @@ -4869,6 +4985,10 @@ void sdhci_remove_host(struct sdhci_host *host, int dead)
> >  
> >  	sdhci_led_unregister(host);
> >  
> > +	if (IS_ENABLED(CONFIG_MMC_SDHCI_UHS2) &&
> > +	    sdhci_uhs2_ops.remove_host)
> > +		sdhci_uhs2_ops.remove_host(host, dead);
> > +
> 
> I think you should look at creating uhs2_remove_host() instead
> 
> >  	if (!dead)
> >  		sdhci_do_reset(host, SDHCI_RESET_ALL);
> >  
> > 
>