On Fri, Jan 28, 2022 at 09:55:04AM +0000, Marc Zyngier wrote:
> On Thu, 27 Jan 2022 20:20:00 +0000,
> Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> > On Mon, Jan 25, 2021 at 04:29:33PM +0000, daire.mcnamara@xxxxxxxxxxxxx wrote:
> > > From: Daire McNamara <daire.mcnamara@xxxxxxxxxxxxx>
> > >
> > > Add support for the Microchip PolarFire PCIe controller when
> > > configured in host (Root Complex) mode.
> >
> > > +static void mc_handle_msi(struct irq_desc *desc)
> > > +{
> > > + struct mc_port *port = irq_desc_get_handler_data(desc);
> > > + struct device *dev = port->dev;
> > > + struct mc_msi *msi = &port->msi;
> > > + void __iomem *bridge_base_addr = port->axi_base_addr + MC_PCIE_BRIDGE_ADDR;
> > > + unsigned long status;
> > > + u32 bit;
> > > + u32 virq;
> > > +
> > > + status = readl_relaxed(bridge_base_addr + ISTATUS_LOCAL);
> > > + if (status & PM_MSI_INT_MSI_MASK) {
> > > + status = readl_relaxed(bridge_base_addr + ISTATUS_MSI);
> > > + for_each_set_bit(bit, &status, msi->num_vectors) {
> > > + virq = irq_find_mapping(msi->dev_domain, bit);
> > > + if (virq)
> > > + generic_handle_irq(virq);
>
> Wrong construct. Please use generic_handle_domain_irq().
I responded to this old posting because it was the most recent one
that included the code below. This irq_find_mapping() bit has since
been updated:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/pci/controller/pcie-microchip-host.c?id=v5.17-rc1#n406
> > > + else
> > > + dev_err_ratelimited(dev, "bad MSI IRQ %d\n", bit);
> > > + }
> > > + }
> > > +}
> > > +
> > > +static void mc_msi_bottom_irq_ack(struct irq_data *data)
> > > +{
> > > + struct mc_port *port = irq_data_get_irq_chip_data(data);
> > > + void __iomem *bridge_base_addr = port->axi_base_addr + MC_PCIE_BRIDGE_ADDR;
> > > + u32 bitpos = data->hwirq;
> > > + unsigned long status;
> > > +
> > > + writel_relaxed(BIT(bitpos), bridge_base_addr + ISTATUS_MSI);
> > > + status = readl_relaxed(bridge_base_addr + ISTATUS_MSI);
> > > + if (!status)
> > > + writel_relaxed(BIT(PM_MSI_INT_MSI_SHIFT), bridge_base_addr + ISTATUS_LOCAL);
> >
> > This looks like it might be racy. What happens if we read 0 from
> > ISTATUS_MSI, but a new MSI is latched before we write ISTATUS_LOCAL?
>
> I agree, this looks really odd. The irq_ack callback is per interrupt,
> while this seems to deal with some global state. This cannot be right.
>
> M.
>
> --
> Without deviation from the norm, progress is not possible.
