xhci-pci: asmedia: Add a firmware loader for ASM2214a chips

Apple ships ASM2214a ICs in some Apple Silicon hardware (notably, the
2021 iMac and the 2022 Mac Studio) without a flash ROM, and relies on
the OS to load firmware on startup. Add support for this to the generic
xhci-pci driver.

The loader code first checks the firmware version, and only attempts to
load firmware if the version isn't the known ROM version.

Since this arrangement only exists on Apple machines so far, and Apple
are the only source of the (non-redistributable) firmware intended for
use on these machines, the firmware is named asmedia/asm2214a-apple.bin.
If this style of firmware loading ever becomes necessary on non-Apple
machines, we should add a generic firmware name at the time (if it can
be part of linux-firmware) or another vendor-specific firmware name.

Signed-off-by: Hector Martin <marcan@marcan.st>

Author: marcan

drivers/usb/host/Kconfig

@@ -51,6 +51,15 @@ config USB_XHCI_PCI_RENESAS
 	  installed on your system for this device to work.
 	  If unsure, say 'N'.
 
+config USB_XHCI_PCI_ASMEDIA
+	bool "Support firmware loading for ASMedia xHCI controllers"
+	default USB_XHCI_PCI if ARCH_APPLE
+	depends on USB_XHCI_PCI
+	help
+	  Say 'Y' to enable support for ASMedia xHCI controllers with
+	  host-supplied firmware. These are usually present on Apple devices.
+	  If unsure, say 'N'.
+
 config USB_XHCI_PLATFORM
 	tristate "Generic xHCI driver for a platform device"
 	help

drivers/usb/host/Makefile

@@ -72,6 +72,8 @@ obj-$(CONFIG_USB_UHCI_HCD)	+= uhci-hcd.o
 obj-$(CONFIG_USB_FHCI_HCD)	+= fhci.o
 obj-$(CONFIG_USB_XHCI_HCD)	+= xhci-hcd.o
 obj-$(CONFIG_USB_XHCI_PCI)	+= xhci-pci.o
+xhci-pci-y                     += xhci-pci-core.o
+xhci-pci-$(CONFIG_USB_XHCI_PCI_ASMEDIA)	+= xhci-pci-asmedia.o
 obj-$(CONFIG_USB_XHCI_PCI_RENESAS)	+= xhci-pci-renesas.o
 obj-$(CONFIG_USB_XHCI_PLATFORM) += xhci-plat-hcd.o
 obj-$(CONFIG_USB_XHCI_HISTB)	+= xhci-histb.o