[PATCH] arm: Improve MMC performance on Versatile Express

[Pawel Moll]

> My final mail on this subject.

Ah, and I was really enjoying our pleasant discussion...

> Take a mainline kernel.  Apply the attached three patches.  MMC
> will then work without any problems.  No hacks required.  There is
> *absolutely* *no* need to waste time with hardware modifications.
> 
> With this you will find that MMCI FIFO underruns/overruns are no
> longer any problem.

$ git log -1
commit d315777b32a4696feb86f2a0c9e9f39c94683649
Merge: 5a05a6d 1765e3a
Author: Linus Torvalds <torvalds at linux-foundation.org>
Date:   Mon Jan 24 19:58:39 2011 +1000
[...]
$ git diff > changes.diff

Attached, I trust you will find all your changes there (and only them).

/ # uname -a
Linux (none) 2.6.38-rc2+ #11 SMP Mon Jan 24 17:11:35 GMT 2011 armv7l GNU/Linux
/ # cat /dev/sda > /dev/null &
/ # dd if=/dev/mmcblk0 of=/dev/null bs=64k count=128
dd: /dev/mmcblk0: Input/output error

And dmesg is full of:
[...]
mmcblk0: error -5 transferring data, sector 254, nr 2, cmd response 0x900, card status 0xb00
end_request: I/O error, dev mmcblk0, sector 254
mmcblk0: error -5 transferring data, sector 255, nr 1, cmd response 0x900, card status 0xb00
end_request: I/O error, dev mmcblk0, sector 255
mmcblk0: error -5 transferring data, sector 0, nr 8, cmd response 0x900, card status 0x900
mmcblk0: retrying using single block read
mmcblk0: error -5 transferring data, sector 0, nr 8, cmd response 0x900, card status 0xb00
[...]

Now:

$ git am 0001-arm-Improve-MMC-performance-on-Versatile-Express.patch

/ # uname -a
Linux (none) 2.6.38-rc2+ #12 SMP Mon Jan 24 17:41:53 GMT 2011 armv7l GNU/Linux
/ # cat /dev/sda > /dev/null &
/ # dd if=/dev/mmcblk0 of=/dev/null bs=64k count=128
128+0 records in
128+0 records out
8388608 bytes (8.0MB) copied, 1.501529 seconds, 5.3MB/s

> THERE IS NO ISSUE WITH MMCI.  THE HARDWARE DOES NOT NEED "FIXING".

I'm really pleased you think so. It's always nice to have happy customers :-)

Cheers!

Paweł
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