Am 04.07.2012 08:57, schrieb Schneider, Kolja:
Am 03.07.2012 20:10, schrieb Marek Vasut:
The commit 5dd95cf93dfffa1d19a1928990852aac9f55b9d9 'usb_storage:
Fix EHCI "out of buffer pointers" with CD-ROM' introduce a bug in
usb_storage as it wrongly assumes that every transfer can use 4k
per qt_buffer. This is wrong if the start address of the data
is not 4k aligned and leads to 'EHCI timed out on TD' messages
because of 'out of buffer pointers' in ehci_td_buffer function.
Cc: Marek Vasut <ma...@denx.de>
Signed-off-by: Stefan Herbrechtsmeier <ste...@herbrechtsmeier.net>
Ok, first I have to admit I broke my promise to look into this ASAP, sorry
about
it :-(
No problem, as long as we get it into the next release. ;-)
Just curious, but shouldn't it be ((4096 * 5) / dev_desc->blk_sz) - 1 ?
No, because the first blk need to be aligned with the 4096. In worst
case the blk is at the end of the 4096 range. If we assume that the blk
is aligned to blk_sz we can change it to ((4096 * 4) / dev_desc->blk_sz)
+ 1. I skip the last blk (+ 1) because with 4096 aligned first blk we
unaligned the next transfer and add extra short packages to each ehci
transfer.
If we want to maximise the usage we need to calculate the max_xfer_blk
depending on the start address of the first blk.
I admit to not totally getting it. However, there are two things that come to
my mind:
- Doesn't the EHCI Specification mention exactly five buffers that
can/should/must
be used?
Yes, you can use up to five 4096 byte buffers.
- I think I once stumbled across some comment that said as much as the
blocks
always having to be aligned anyway?
The buffers must be aligned to a 4096 byte page. This means that you
have to use the first and last buffer to align your data to the next or
previous 4096 byte page boundary.
_______________________________________________
U-Boot mailing list
U-Boot@lists.denx.de
http://lists.denx.de/mailman/listinfo/u-boot
