XHCI bringup on the Raspberry Pi 4

[Nicolas Saenz Julienne]

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 :(

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