Re: [PATCH v3 08/10] PCI: apple: Implement MSI support

[Marc Zyngier <maz@kernel.org>]

On Mon, 13 Sep 2021 21:43:23 +0100,
Alyssa Rosenzweig <alyssa@rosenzweig.io> wrote:
> 
> > +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).

Indeed, this makes a bit more sense. Thanks for pointing this out.

	M.

-- 
Without deviation from the norm, progress is not possible.