[U-Boot] xHCI on x86

Hi!

I'm currently trying to get xHCI working on some BayTrail based x86 boards. For this I've added DM support to xhci-pci and made a small change to cache.h to enable compilation of the xhci driver on x86 (please find those 2 patches attached - I'll send then to the list once this is resolved). But I noticed that the xhci driver hangs in xhci_queue_command() in this line:

xhci_writel(&ctrl->dba->doorbell[0], DB_VALUE_HOST);

when first writing to the doorbell register. Reading from this doorbell register still works just fine.

IIRC, Simon has mentioned that xHCI still has some "issues" on x86. Simon, is this what you have seen as well? Does anyone have some ideas how to solve this?

Thanks, Stefan