linux-kernel - Re: [PATCH 3/3] sdhci-pltfm: Add support for CNS3xxx SoC devices

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Date:	Thu, 8 Jul 2010 19:36:29 +0400
From:	Anton Vorontsov <cbouatmailru@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ben Dooks <ben@...tec.co.uk>,
	Richard Röjfors <richard.rojfors@...agicore.com>,
	linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] sdhci-pltfm: Add support for CNS3xxx SoC devices

Sorry for the delayed response,

On Thu, Jul 01, 2010 at 01:48:39PM -0700, Andrew Morton wrote:
> On Fri, 25 Jun 2010 22:06:44 +0400
> Anton Vorontsov <avorontsov@...sta.com> wrote:
> 
> > There's nothing special, just SoC-specific ops and quirks.
> > 
> > ...
> >
> > +static void sdhci_cns3xxx_set_clock(struct sdhci_host *host, unsigned int clock)
> > +{
> > +	struct device *dev = mmc_dev(host->mmc);
> > +	int div = 1;
> > +	u16 clk;
> > +	unsigned long timeout;
> > +
> > +	if (clock == host->clock)
> > +		return;
> 
> I assume that mmc core prevents this function from being exectued twice
> at the same time?

Yep, it's called under spin_lock_irqsave(&host->lock, flags).

[...]
> > +	timeout = 20;
> > +	while (!((clk = sdhci_readw(host, SDHCI_CLOCK_CONTROL))
> > +			& SDHCI_CLOCK_INT_STABLE)) {
> > +		if (timeout == 0) {
> > +			dev_warn(dev, "clock is unstable");
> > +			break;
> > +		}
> > +		timeout--;
> > +		mdelay(1);
> 
> Could we have used the more polite msleep() here?

Unfortunately not, we're in the atomic context.

[...]
> > --- a/drivers/mmc/host/sdhci-pltfm.c
> > +++ b/drivers/mmc/host/sdhci-pltfm.c
> > @@ -158,6 +158,9 @@ static int __devexit sdhci_pltfm_remove(struct platform_device *pdev)
> >  
> >  static const struct platform_device_id sdhci_pltfm_ids[] = {
> >  	{ "sdhci", },
> > +#ifdef CONFIG_MMC_SDHCI_CNS3XXX
> > +	{ "sdhci-cns3xxx", (kernel_ulong_t)&sdhci_cns3xxx_pdata },
> > +#endif
> 
> What the heck is this kernel_ulong_t thing and why did `struct
> platform_device_id' see a need to invent it??

It's not only platform_device_id's thing. Sometimes drivers just
pass a constant instead of a pointer (e.g. DEVICE_IS_FOO,
DEVICE_IS_BAR), for example see drivers/hwmon/lm75.c (enum
lm75_type).

Other than this I don't think that there's a good reason for it.

Thanks,

-- 
Anton Vorontsov
email: cbouatmailru@...il.com
irc://irc.freenode.net/bd2
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