Hi Manoj,

On Mon, Jul 18 2011, Manoj Iyer wrote:
> Right, without the patch I get..
>
> [   52.526665] mmc0: new SDHC card at address e624
> [   52.571228] mmcblk0: mmc0:e624 SD16G 14.8 GiB
> [   52.591071] mmcblk0: retrying using single block read
> [   52.593105] mmcblk0: error -84 transferring data, sector 0, nr 8,
> card status 0x900
> [   52.593109] end_request: I/O error, dev mmcblk0, sector 0
> [   52.594594] mmcblk0: error -84 transferring data, sector 1, nr 7,
> card status 0x900
> [   52.594604] end_request: I/O error, dev mmcblk0, sector 1
> [   52.602893] quiet_error: 24 callbacks suppressed
> [   52.602902] Buffer I/O error on device mmcblk0, logical block 0
> [   52.605349] ldm_validate_partition_table(): Disk read failed.
> [   52.605384] Dev mmcblk0: unable to read RDB block 0
> [   52.607729]  mmcblk0: unable to read partition table
> u@u:~$
>
> So, I cannot generate any comparison data with this SD card.

I see, thanks.  So we're lacking any data on what speed the card would
normally provide.  Perhaps you could try that card on a different
controller, just so we're able to see whether it's usually possible
to get closer to 45M/sec with it?

I think I'll take your patch as-is for 3.1 -- since if there is a
performance degradation, it's on cards that simply don't work at all
right now -- and if you're able to work on a followup patch that only
performs the clock-lowering after the first error, I think that'd be a
handy patch to have around.  Does that sound good?

Thanks!

- Chris.
-- 
Chris Ball   <cjb@laptop.org>   <http://printf.net/>
One Laptop Per Child