[U-Boot-Users] drivers MMCplus for at91sam9x

[Ken.Fuchs at bench.com]

Congratulations!  It will be great to have MMC v4.x support in U-Boot.

The following segment of code from
linux-2.6.25-rc9/drivers/mmc/host/at91_mci.c is confusing:

if (host->board->wire4) {
        if (cpu_is_at91sam9260() || cpu_is_at91sam9263())
                mmc->caps |= MMC_CAP_4_BIT_DATA;
        else
                dev_warn(&pdev->dev, "4 wire bus mode not supported"
                        " - using 1 wire\n");
}

This code seems to imply that MMC 4 bits works on the AT91SAM9260 and
AT91SAM9263, but not any of the others in this processor family,
possibly due to a hardware bug.  Any comments on why the Linux AT91 MCI
driver doesn't support an 4 bit MMC bus for all AT91SAM9 processors?

I mention this because it may impact the AT91 MCI U-Boot device driver.

Sincerely,

Ken Fuchs

> -----Original Message-----
> From: u-boot-users-bounces at lists.sourceforge.net 
> [mailto:u-boot-users-bounces at lists.sourceforge.net] On Behalf 
> Of Andy Fleming
> Sent: Tuesday, April 15, 2008 14:25
> To: Pierre Savary
> Cc: u-boot-users at lists.sourceforge.net; drzeus-mmc at drzeus.cx
> Subject: Re: [U-Boot-Users] drivers MMCplus for at91sam9x
> 
> 
> On Tue, Apr 15, 2008 at 5:18 AM, Pierre Savary 
> <pierre.savary at kerlink.fr> wrote:
> > Then my MMC 4GB works with my Linux kernel but if I can't 
> load my kernel
> >  (located on the first part of this MMC) ... it's not 
> really interesting :(
> >
> >  So, somebody does already use MMC v4 with U-boot???
> 
> I've got one that works.  However, I don't have a 4GB MMC card with
> v4.  I thought I did, but it turned out the card just takes advantage
> of the fact that older versions can address 4GB, even though the spec
> says 2GB is the max.
> 
> However, I'm fairly confident in the code (it's been tested in
> simulated environments, and reflects what the Linux code does).  I'm
> currently working on bringing it forward to the top of tree (I started
> it before drivers/ got rearranged).  I'm actually hoping to generalize
> it some so we can share it between all MMC/SD users.
> 
> Andy
> 
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