[U-Boot] XHCI Issues

[Aaron Williams]

Hi all,

I am bringing up XHCI support for our SOC and have run into several 
issues with U-Boot's XHCI code.

1. I need to use a wrapper I call xhci_readl/xhci_writel since all of 
our I/O is to 64-bit addresses rather than readl/writel which work for 
PCIe. While xhci_readl/xhci_writel is used in most places there are a 
few places this is missing.

2. A memory address used by a pointer is not a DMA address on MIPS. On 
MIPS a wrapper is needed for all read/write operations to descriptors to 
map the addresses. Generally U-Boot runs in KSEG0 where a pointer always 
has bit 31 set. In our case we run it in virtual memory with U-Boot 
loaded at the top of memory (which might be as high as 64GB+256MB).

3. xhci_alloc_virt_device is missing a conversion from big endian to 
little endian on line 401 of xhci-mem.c.

4. I keep getting hit with

BUG_ON(GET_COMP_CODE(le32_to_cpu(event->trans_event.transfer_len
         != COMP_STOP)));
on line 491 in xhci-ring.c. Commenting this out seems to work fine.

5. I also hit the BUG_ON on line 722 of xhci-ring.c since on MIPS a 
pointer is not a DMA address and the fact that we use 64-bit addresses 
where pointers are 32-bits.

I ran into similar issues with EHCI where again we have to map pointers 
to physical addresses and use our own wrappers for register accesses.

At some point I would love to merge our stuff back into the mainline 
U-Boot but it's going to be a huge job given that we probably have 
almost 250K lines of code involved for our MIPS SOCs.

-Aaron

-- 
Aaron Williams
Software Engineer
Cavium, Inc.
(408) 943-7198  (510) 789-8988 (cell)