XHCI bringup on the Raspberry Pi 4

[Marek Vasut]

On 4/1/20 10:13 PM, Nicolas Saenz Julienne wrote:
> On Wed, 2020-04-01 at 20:50 +0200, Marek Vasut wrote:
>> On 4/1/20 7:30 PM, Nicolas Saenz Julienne wrote:
>>> Hi All,
>>
>> Hi,
>>
>>> I'm working on enabling the VIA805 XCHI controller found on the new
>>> Raspberry
>>> Pi 4. The controller sits behind a PCIe bus, which I've already
>>> implemented[1]
>>> and will submit once the XCHI issues are resolved, as it's worthless
>>> otherwise.
>>>
>>> The XHCI initialization gets stuck after issuing the fist 'enable slot'
>>> command. I've been reviewing the whole init process and comparing it to
>>> Linux's
>>> for days without finding anything fishy. DMA constraints, which are
>>> important
>>> on the RPi are mantained, and on top of that, I can confirm DMA trough PCIe
>>> works fine as I see two 'port status change' events available in the ring
>>> before completly stalling. Also note that, unsurprisingly, the CRR bit in
>>> the
>>> CRCR register (which marks the running state of the Command Ring state
>>> machine)
>>> is never set after ringing the relevant doorbell.
>>>
>>> I'm clueless at this point, I figure the VIA805 is sensitive to the ordering
>>> of
>>> some of the operations we perform in u-boot, or worse, the timing. For
>>> example,
>>> I tried replicanting Linux's behaviour with regard to 'port status change'
>>> events, processing them before calling the 'enable slot' command. I also
>>> tried
>>> to mimic Linux by enabling port-0's power (the USB3 port) before starting
>>> the
>>> HC. Again, no luck.
>>>
>>> I attached the usb/xhci debug output, any ideas on where to look will be
>>> apreciated.
>>
>> Try disabling caches (dcache off ; icache off) and see if it magically
>> starts working. That comes to mind.
> 
> Same outcome :(

Hmmm, no idea then, maybe others have some.

I presume PCIe works correctly , right?