Re: [PATCH v3] OMAP: Fix for bus width which improves SD card'speformance.

[Felipe Balbi]

On Tue, Apr 06, 2010 at 06:16:01PM +0200, ext Madhusudhan wrote:
> > -----Original Message-----
> > From: Felipe Balbi [mailto:me@xxxxxxxxxxxxxxx]
> > Sent: Tuesday, April 06, 2010 12:01 AM
> > To: Madhusudhan
> > Cc: me@xxxxxxxxxxxxxxx; 'kishore kadiyala'; 'Vimal Singh';
> > tony@xxxxxxxxxxx; svenkatr@xxxxxx; linux-omap@xxxxxxxxxxxxxxx; linux-
> > kernel@xxxxxxxxxxxxxxx; jarkko.lavinen@xxxxxxxxx
> > Subject: Re: [PATCH v3] OMAP: Fix for bus width which improves SD card's
> > peformance.
> >
> > Hi,
> >
> > On Mon, Apr 05, 2010 at 12:19:29PM -0500, Madhusudhan wrote:
> > > Since the first if command already checks for the 8-bit the second check
> > > like >= 4 is definitely not readable in my opinion.
> >
> > how come ???
> >
> > > Functionally do you see anything wrong with this patch??
> >
> > functionally no, but (hypothetical situation) and if on
> > omap4/5/6/whatever, omap controller supports a bigger bus width then
> > you'll have to add a line like:
> >
> > +	if (mmc_slot(host).wires == 16)
> > +		mmc->caps |= (MMC_CAP_16_BIT_DATA | MMC_CAP_8_BIT_DATA |
> > +				MMC_CAP_4_BIT_DATA);
> > -	if (mmc_slot(host).wires == 8)
> > +	else if (mmc_slot(host).wires == 8)
> >
> > do you see the problem ?? In my opinion it doesn't scale well.
>
> The point we should note here is that MMC spec supports a max bus width of
> 8-bit. So anything beyond 8-bit is not in the picture as of today.

in that case, the code could be:

WARN_ON(mmc_slot(host).wires > 8);

if (mmc_slot(host).wires == 8)
	mmc->caps |= MMC_CAP_8_BIT_DATA;
if (mmc_slot(host).wires >= 4)
	mmc->caps |= MMC_CAP_4_BIT_DATA;

--
balbi
--
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/