[nokosaaan]

Description

Add a polled xHCI host controller driver that detects xHCI controllers and brings them up. This PR covers controller initialization only; device enumeration and the USB serial console come in follow-up PRs.

What this PR does:

• Detection: PCIeInfo::attach() routes Serial Bus Controllers with sub-class 0x03 / prog-if 0x30 to pcie::usb::attach(), before vendor-based matching, so controllers are handled regardless of silicon vendor.
• Bring-up (xHCI spec §4.2):
  • waits for CNR, halts the controller if it is running, and issues HCRST;
  • re-enables PCI Bus Master (it may be cleared by HCRST or at ExitBootServices) and checks that it stuck;
  • programs MaxSlotsEn, DCBAAP, CRCR and Interrupter 0 (ERSTSZ / ERSTBA / ERDP);
  • allocates scratchpad buffers and stores their array in DCBAA[0];
  • sets Run/Stop and waits for HCHalted to clear.
• Smoke test: submits a No-Op command and waits for its Command Completion event, which confirms that the command and event rings work end to end.
• Build: adds the xhci feature to awkernel_drivers and enables it in the kernel's x86 feature set, so CI compiles and lints the driver.

New files:

File	Contents
pcie/usb/mod.rs	class check, attach entry point, lint gates
pcie/usb/xhci/mod.rs	controller core (command / event ring handling, doorbells) and initialization
pcie/usb/xhci/ring.rs	producer ring (Command Ring), Event Ring + ERST, DCBAA
pcie/usb/xhci/regs.rs	register offsets, TRB types/flags, completion codes

Related links

previous PR: #731

How was this PR tested?

• scripts/ci.sh passes on my machine.
• QEMU (-device qemu-xhci with a USB keyboard and usb-net attached) boots to the shell with the following log and no panic:

  xHCI: 0000:00:03.0 xHCI: controller running (polled)
  xHCI: 0000:00:03.0 xHCI: NOOP command OK — command ring is alive
  ...
  All CPUs are ready.
  

• make qemu-x86_64

Notes for reviewers

[ytakano]

@nokosaaan

Why don't you add -device qemu-xhci to QEMU_X86_ARGS of Makefile?

awkernel/Makefile

Lines 160 to 173 in 54d8757

	QEMU_X86_ARGS= -drive if=pflash,format=raw,readonly=on,file=${OVMF_PATH}/code.fd
	QEMU_X86_ARGS+= -drive if=pflash,format=raw,file=${OVMF_PATH}/vars_qemu.fd
	QEMU_X86_ARGS+= -drive format=raw,file=x86_64_uefi.img
	QEMU_X86_ARGS+= -machine q35
	QEMU_X86_ARGS+= -serial stdio -smp 4 -monitor telnet::5556,server,nowait
	QEMU_X86_ARGS+= -m 4G -smp cpus=16
	QEMU_X86_ARGS+= -object memory-backend-ram,size=1G,id=m0
	QEMU_X86_ARGS+= -object memory-backend-ram,size=1G,id=m1
	QEMU_X86_ARGS+= -object memory-backend-ram,size=1G,id=m2
	QEMU_X86_ARGS+= -object memory-backend-ram,size=1G,id=m3
	QEMU_X86_ARGS+= -numa node,memdev=m0,cpus=0-3,nodeid=0
	QEMU_X86_ARGS+= -numa node,memdev=m1,cpus=4-7,nodeid=1
	QEMU_X86_ARGS+= -numa node,memdev=m2,cpus=8-11,nodeid=2
	QEMU_X86_ARGS+= -numa node,memdev=m3,cpus=12-15,nodeid=3

[nokosaaan]

@ytakano
Thanks, added -device qemu-xhci,id=xhci to QEMU_X86_ARGS (it also applies to qemu-x86_64-net / -nographic).