Yes, I have tried the first suggestion from Matthias Fuchs. But make it working with cache is very complex. So now I am trying the way that map one TLB entry to make USB hcca and data struct in uncached region. I think it's a easy way but not suitable for other platform.
Best Regards, Ryan Chen
-----Original Message----- From: Markus Klotzbücher [mailto:mk@denx.de] Sent: Saturday, May 17, 2008 12:25 AM To: Matthias Fuchs Cc: u-boot-users@lists.sourceforge.net; Ryan CHEN; ebenard@eukrea.com; weissg@vienna.at; Zhang Wei Subject: Re: [U-Boot-Users] U-Boot help request for OHCI driver with CPU cache on
Hi Matthias,
Matthias Fuchs matthias.fuchs@esd-electronics.com writes:
On Thursday 15 May 2008 10:37:04 Markus Klotzbücher wrote:
Could you suggest me how to solve the problem? Is there any specific part of USB driver that requires cache handling?
None that I'm aware of, but I could imagine that enabling caches might cause some kind of problems.
With U-Boot's current OHCI implementation you will run into trouble at least with cache incoherent CPUs like the 4xx PowerPCs. The 4xx_enet driver has been modified to deal with this stuff when data caches are enabled. The USB OHCI driver will also need that kind of fixing (making the code very ugly). An other approach would be to put the USB DMA accessable memory into some non-cached memory. Perhaps this is much more simple.
Thanks for the explanation. Yes I agree that this is likely the problem.
I'm wondering if the benefits of having the cache enabled is worth the pain of fixing (= making the code uglier) this at all. I somehow doubt it.
Best regards
Markus Klotzbuecher
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