[U-Boot] XHCI Issues

[Aaron Williams]

On 01/13/2014 06:20 PM, Aaron Williams wrote:
> 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
>
I have a follow-up:

I am seeing error messages when hub ports are reset.

In the output below I have a USB 3 thumb drive plugged into USB0 and a 
USB 2 thumb drive plugged into USB1. Each USB device has "2" ports, 
where port 0 is treated as a USB 3 port and port 1 is treated as a USB 
1/2 port. I think the "cannot reset port X!?" message is invalid since 
otherwise everything appears to be working.

I am also seeing rather slow transfers of around 1.9MiB/sec. Is this 
normal for XHCI? This is for both USB 2 and a high-speed USB 3 thumb 
drive when loading a 40MiB Linux kernel image.

-Aaron

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