Re: [PATCH] OMAP: MMC: recover from transfer failures - Resend
From: David Brownell
Date: Sun Feb 08 2009 - 15:27:27 EST
On Thursday 05 February 2009, Paul Walmsley 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.
It's still good policy to have a cpu_relax() in
such loops. Not that it'll do much on most ARMs,
but empty statements are in general worth avoiding.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/