linux-kernel - Re: [PATCH] OMAP: MMC: recover from transfer failures

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Message-Id: <200902061422.32689.jpihet@mvista.com>
Date:	Fri, 6 Feb 2009 14:22:32 +0100
From:	Jean Pihet <jpihet@...sta.com>
To:	Paul Walmsley <paul@...an.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	tony@...mide.com, ext-adrian.hunter@...ia.com,
	linux-arm-kernel@...ts.arm.linux.org.uk,
	linux-omap@...r.kernel.org, jarkko.lavinen@...ia.com,
	drzeus-mmc@...eus.cx, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] OMAP: MMC: recover from transfer failures - Resend

On Thursday 05 February 2009 21:32:03 Paul Walmsley wrote:
> On Thu, 5 Feb 2009, Andrew Morton wrote:
> > On Tue, 3 Feb 2009 15:05:58 +0100
> >
> > Jean Pihet <jpihet@...sta.com> wrote:
> > > +	while (OMAP_HSMMC_READ(host->base,
> > > + 			SYSCTL) & SRD)
> > > + 		;
> >
> > Is a __raw_readl() sufficient to prevent the cpu from burning up here,
> > or should we add cpu_relax()?
>
> The __raw_readl() should be sufficient.  The MMC controller is located on
> the L4 CORE interconnect, so the round trip latency for the read from MMC
> is at least 90 ns, while the CPU cycle time is only about 1 to 2 ns.
Ok.
>
> > An infinite loop which assumes the hardware is perfect is always a
> > worry.  But I see the driver already does that, so we're no worse off..
Do you want a finite loop with udelay in it? I located 4 places were this 
could be used. If so I can generate a new patch for that.

>
> - Paul

Regards,
Jean
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