linux-kernel - Re: [RFC PATCH V3 12/21] mmc: sdhci: UHS-II support, add hooks for additional operations

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Message-ID: <20200917023113.GB3071249@laputa>
Date:   Thu, 17 Sep 2020 11:31:13 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     Adrian Hunter <adrian.hunter@...el.com>
Cc:     Ben Chuang <benchuanggli@...il.com>, 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 12/21] mmc: sdhci: UHS-II support, add hooks for
 additional operations

Adrian,

On Wed, Sep 16, 2020 at 01:00:35PM +0300, Adrian Hunter wrote:
> On 16/09/20 11:05 am, AKASHI Takahiro wrote:
> > Adrian,
> > 
> > Your comments are scattered over various functions, and so
> > I would like to address them in separate replies.
> > 
> > First, I'd like to discuss sdhci_[add|remove]_host().
> > 
> > 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@...esyslogic.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@...esyslogic.com.tw>
> >>> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>
> >>> ---
> > 
> >  (snip)
> > 
> >>>  		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
> > 
> > You suggest that we will have separate sdhci_uhs2_[add|remove]_host(),
> > but I don't think it's always convenient.
> > 
> > UHS-II capable host will be set to call sdhci_uhs2_add_host() explicitly,
> > but we can't do that in case of pci and pltfm based drivers as they utilize
> > common helper functions, sdhci_pci_probe() and sdhci_pltfm_register(),
> > respectively.
> 
> sdhci-pci has an add_host op
> 
> sdhci_pltfm_init can be used instead of sdhci_pltfm_register
> 
> 
> > Therefore, we inevitably have to call sdhci_uhs2_add_host() there.
> > 
> > If so, why should we distinguish sdhci_uhs2_add_host from sdhci_uhs_add_host?
> > I don't see any good reason.
> > Moreover, as a result, there exists a mixed usage of sdhci_ interfaces
> > and sdhci_uhs2_ interfaces in sdhci-pci-core.c and sdhci-pltfm.c.
> > 
> > It sounds odd to me.
> 
> It is already done that way for cqhci.

Okay, if it is your policy, I will follow that.
Then, I'm going to add
- remove_host field to struct sdhci_pci_fixes
- a controller specific helper function to each driver (only pci-gli for now)
  even though it looks quite generic.

  sdhci_gli_[add|remove]_host(struct sdhci_pci_slot *slot)
  {
      return sdhci_uhs2_[add|remove]_host(slot->host);
  }

# Or do you want to create a file like sdhci-uhs2-pci.c for those functions?

-Takahiro Akashi

> > 
> > -Takahiro Akashi
> > 
> > 
> >>
> >>>  	if (!dead)
> >>>  		sdhci_do_reset(host, SDHCI_RESET_ALL);
> >>>  
> >>>
> >>
>