[U-Boot] [PATCH 1/2 v2] SDHC/MMC: fix the wrong infomation after change SD card

[Huang Changming-R66093]

Hi, Andy
Could you give some reason why eMMC device will be so slowed down by re-initialization?
I think eMMC device is initialized only once, except it invoke 'mmc_init' many times.

The workaround "mmc rescan" works when replace the card.
But if one card is removed, then use "mmcfinfo": there is no card present, while the previous card information is displayed, I don't' think it make sense.
=> mmc rescan
MMC: no card present
=> mmcinfo
MMC: no card present
Device: FSL_SDHC
Manufacturer ID: 2
OEM: 544d
Name: SD04G
Tran Speed: 50000000
Rd Block Len: 512
SD version 2.0
High Capacity: Yes
Capacity: 3.7 GiB
Bus Width: 4-bit

Best Regards
Jerry Huang


> -----Original Message-----
> From: Andy Fleming [mailto:afleming at gmail.com]
> Sent: Saturday, July 14, 2012 5:33 AM
> To: Huang Changming-R66093
> Cc: u-boot at lists.denx.de; Marek Vasut
> Subject: Re: [PATCH 1/2 v2] SDHC/MMC: fix the wrong infomation after
> change SD card
> 
> On Wed, Jul 11, 2012 at 4:29 AM, Huang Changming-R66093
> <r66093 at freescale.com> wrote:
> > Hi, Andy,
> > There is not any feedback for very long time,
> > Could it be applied to the u-boot?
> 
> 
> I'm afraid I have to reject this patch. We need to find a better
> solution to the two problems:
> 
> 1) We want to change cards and still have mmc commands work
> 2) We don't want eMMC devices to be slowed down by constantly
> re-initializing their cards.
> 
> Normally, I would err on the side of #1, but there's a simple
> workaround. If you replace the card, execute "mmc rescan", and the
> card will be reinitialized. Please let me know if that workaround
> doesn't work. I hope, in the future, we'll have some code which makes
> both possible, by being able to detect that a card has been changed,
> but for now I think the current system is reasonably satisfactory to
> both cases #1 and #2.
> 
> Andy