Hi,
2010/10/22 Wolfgang Denk wd@denx.de:
This patch solves a problem with USB hanging under higher load on a i.MX31 board. It falls into class of typical USB problems and fixes: if you don't understand the real cause, add a delay somewhere.
The problem appeared after introduction of ELF relocation, which results in smaller code, which appears to run faster (probably because it fits better in the cache); turning off the instruction cache, adding debug printf()s and increasing the delay have all been found to make the problem go away.
Moving the original "udelay(1)" up in the code to it's new place made the problem appear much less frequently. Increasing the delay to 2 microseconds then made the code run reliably in all (hour-long) tests. To be on the safe side, we set it to 5 microseconds here.
Signed-off-by: Heiko schocher hs@denx.de Signed-off-by: Wolfgang Denk wd@denx.de Cc: Remy Bohmer linux@bohmer.net Cc: Stefano Babic sbabic@denx.de
drivers/usb/host/ehci-hcd.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
Not nice, but I do not see how this could harm something. Applied to u-boot-usb.
Kind regards,
Remy