XHCI bringup on the Raspberry Pi 4

[Marek Vasut]

On 4/1/20 10:47 PM, Nicolas Saenz Julienne wrote:
> On Wed, 2020-04-01 at 22:14 +0200, Marek Vasut wrote:
>> 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?
> 
> I was also responsible for the Linux version of the PCIe driver so I know it
> fairly well. I also double-checked all pcie-brcmstb's registers have the
> expected values.
> 
> From the USB perspective, I'm both able to map XHCI's registers into memory and
> get some output out of the event ring, which implies XHCI accessed memory
> trough the bus. On top of that if something went wrong with PCI there is a
> register that should point it out, Host System Error (HSE), which so far has
> been silent.
> 
> Overall I'm confident PCIe is fine.

OK, then I hope Bin can help here, he's the xHCI expert.