IIR
iir = xe_mmio_read32(mmio, IIR(GU_MISC_IRQ_OFFSET));
xe_mmio_write32(mmio, IIR(GU_MISC_IRQ_OFFSET), iir);
assert_iir_is_zero(mmio, IIR(irqregs));
xe_mmio_write32(mmio, IIR(irqregs), ~0);
xe_mmio_read32(mmio, IIR(irqregs));
xe_mmio_write32(mmio, IIR(irqregs), ~0);
xe_mmio_read32(mmio, IIR(irqregs));
i810_readw(IIR, mmio),