> +static void apple_msi_compose_msg(struct irq_data *data, struct msi_msg *msg) > +{ > + BUILD_BUG_ON(upper_32_bits(DOORBELL_ADDR)); > + > + msg->address_hi = upper_32_bits(DOORBELL_ADDR); > + msg->address_lo = lower_32_bits(DOORBELL_ADDR); > + msg->data = data->hwirq; > +} ... > @@ -269,6 +378,14 @@ static int apple_pcie_port_setup_irq(struct apple_pcie_port *port) > > irq_set_chained_handler_and_data(irq, apple_port_irq_handler, port); > > + /* Configure MSI base address */ > + writel_relaxed(lower_32_bits(DOORBELL_ADDR), port->base + PORT_MSIADDR); > + > + /* Enable MSIs, shared between all ports */ > + writel_relaxed(0, port->base + PORT_MSIBASE); > + writel_relaxed((ilog2(port->pcie->nvecs) << PORT_MSICFG_L2MSINUM_SHIFT) | > + PORT_MSICFG_EN, port->base + PORT_MSICFG); > + > return 0; > } I think the BUILD_BUG_ON makes more sense next to configuring the base address (which only has a 32-bit register, the BUILD_BUG_ON justifies using writel and not writeq), rather than configuring the message (which specifies the full 64-bits).