According to xHCI spec Figure 30: Interrupt Throttle Flow Diagram
If PCI Message Signaled Interrupts (MSI or MSI-X) are enabled,
then the assertion of the Interrupt Pending (IP) flag in Figure 30
generates a PCI Dword write. The IP flag is automatically cleared
by the completion of the PCI write.
the MSI enabled HCs don't need to clear interrupt pending bit, but
hcd->irq = 0 doesn't equal to MSI enabled HCD. At some Dual-role
controller software designs, it sets hcd->irq as 0 to avoid HCD
requesting interrupt, and they want to decide when to call usb_hcd_irq
by software.
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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