linux-kernel - Re: [PATCH 05/18] MMC: OMAP: Introduce new multislot structure and change driver to use it

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Date:	Wed, 5 Mar 2008 22:54:09 +0200
From:	Felipe Balbi <me@...ipebalbi.com>
To:	Pierre Ossman <drzeus-list@...eus.cx>
Cc:	Carlos Aguiar <carlos.aguiar@...t.org.br>,
	Tony Lindgren <tony@...mide.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/18] MMC: OMAP: Introduce new multislot structure and
	change driver to use it

On Thu, Feb 07, 2008 at 06:37:44PM +0100, Pierre Ossman wrote:
> On Mon, 28 Jan 2008 15:07:23 -0400
> Carlos Aguiar <carlos.aguiar@...t.org.br> wrote:
> 
> > From: Juha Yrjola <juha.yrjola@...idboot.com>
> > 
> > Introduce new MMC multislot structure and change driver to use it.
> > 
> > Note that MMC clocking is now enabled in mmc_omap_select_slot()
> > and disabled in mmc_omap_release_slot().
> > 
> > Signed-off-by: Juha Yrjola <juha.yrjola@...idboot.com>
> > Signed-off-by: Jarkko Lavinen <jarkko.lavinen@...ia.com>
> > Signed-off-by: Carlos Eduardo Aguiar <carlos.aguiar@...t.org.br>
> > Signed-off-by: Tony Lindgren <tony@...mide.com>
> > ---
> 
> I still think this muxed mmc host thing is a bad idea, but it's your nightmare...

Not nightmare. OMAP1/2 have mmc/sd/sdio controller supporting one or
more mmc cards sharing the same bus.

> 
> > +
> > +/* Access to the R/O switch is required for production testing
> > + * purposes. */
> > +static ssize_t
> > +mmc_omap_show_ro(struct device *dev, struct device_attribute *attr, char *buf)
> > +{
> > +	struct mmc_host *mmc = container_of(dev, struct mmc_host, class_dev);
> > +	struct mmc_omap_slot *slot = mmc_priv(mmc);
> > +
> > +	return sprintf(buf, "%d\n", slot->pdata->get_ro(mmc_dev(mmc),
> > +							slot->id));
> > +}
> > +
> > +static DEVICE_ATTR(ro, S_IRUGO, mmc_omap_show_ro, NULL);
> > +
> 
> This is unrelated to the slot stuff and should be in its own patch. Also, it should probably be in the core, not a driver.
> 
> > +
> > +	mmc->caps = MMC_CAP_MULTIWRITE | MMC_CAP_MMC_HIGHSPEED |
> > +		    MMC_CAP_SD_HIGHSPEED;
> 
> This is also unrelated. From what I've seen, the OMAP is a SD controller and does not support high speed MMC. The fact that you also conditionally set the max frequency later also suggests that this code is entirely incorrect.
> 

Not true. I can't show you not even parts of the technical documentation
but OMAP has mmc/sd/sdio controller. On OMAP1/2 it handles several mmc
cards sharing the same bus.

And that's what mmc multislot is doing. Probably it still needs some
tweks though. But that's up to Carlos.

> > +
> > +	r = mmc_add_host(mmc);
> > +	if (r < 0)
> > +		return r;
> > +
> > +	if (slot->pdata->name != NULL) {
> > +		r = device_create_file(&mmc->class_dev,
> > +					&dev_attr_slot_name);
> > +		if (r < 0)
> > +			goto err_remove_host;
> > +	}
> > +
> > +	if (slot->pdata->get_ro != NULL) {
> > +		r = device_create_file(&mmc->class_dev,
> > +					&dev_attr_ro);
> > +	}
> > +
> 
> You have a bit of a race here with userspace in case you use the uevent to trigger things.
> 
> -- 
>      -- Pierre Ossman
> 
>   Linux kernel, MMC maintainer        http://www.kernel.org
>   PulseAudio, core developer          http://pulseaudio.org
>   rdesktop, core developer          http://www.rdesktop.org
> --
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-- 
Best Regards,

Felipe Balbi
me@...ipebalbi.com
http://blog.felipebalbi.com
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