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

David Brownell
2009-02-08T20:27:20Z

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.