linux-kernel - Re: [PATCH] sdhci: fix undue iomem warning

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Message-Id: <201105302033.12409.arnd@arndb.de>
Date:	Mon, 30 May 2011 20:33:12 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Wolfram Sang <w.sang@...gutronix.de>
Cc:	Daniel J Blueman <daniel.blueman@...il.com>,
	Chris Ball <cjb@...top.org>, linux-mmc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sdhci: fix undue iomem warning

On Monday 30 May 2011 20:21:03 Wolfram Sang wrote:
>   Show Details
>   > > a) SDHC Specs (even v3) only mention 0x100, so this is the standard.
> > >   Do the new cards (which ones?) have anything located in the extra
> > >   area?
> > 
> > This controller is a dual-slot one, so has two register sets (though
> > one set of pins aren't wired to a socket).
> 
> There are two controllers and they are packed into one PCI-bar? :( I guess this
> needs refactoring of the probe_slot routine then. Just silencing the warning
> will just hide the problem.

Right. Presumably someone has already built a different system with the
same chip and both slots in use. This probably also means we need a
way to figure out which of the slots are in fact connected.

> > > b) your approach won't scale very well
> > 
> > True - a more scalable test would be to check for non-zero length and
> > a multiple of 256 bytes, would you say?
> 
> That wouldn't alarm for 0x10000 or the like, so no gain as well.

In fact, all PCI resources are by definition power-of-two numbers,
so the check would not work at all.

> > >> +             dev_warn(&pdev->dev, "Invalid iomem size. You may "
> > >>                       "experience problems.\n");
> > >
> > > I second turning the message into a warning, though.
> > 
> > If the latter method is preferred, I'll adjust the patch and resend.
> 
> Reconsidering: Given the current situation, an error message is maybe not a
> that bad idea, until the code can handle two controllers in one bar.

Agreed.

	Arnd
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