On Wed, Apr 26, 2017 at 11:15 AM, Lucas Stach <l.stach@xxxxxxxxxxxxxx> wrote:
> The DWC host does not support legacy PCI IRQs and MSIs at the same time,
> so we need to fall back to using only legacy IRQs if there is a chance
> that multiple devices with differing MSI capabilities are connected to
> the host. The only configuration where MSIs can be safely used is when
> the device below the host bridge is not a bridge, i.e. the only device
> connected to this host.
>
> By disallowing MSI allocation when multiple devices might be attached
> we get those configurations in a working state. The only configurations
> that depend on MSIs being available, that I am aware of, are some
> embedded devices with a PCIe attached FPGA, that is incapable of
> generating PCI legacy IRQs. Those are kept working by allowing MSIs
> when only a single device is attached to the host.
>
> Signed-off-by: Lucas Stach <l.stach@xxxxxxxxxxxxxx>
> ---
> drivers/pci/dwc/pcie-designware-host.c | 24 ++++++++++++++++++++++--
> drivers/pci/dwc/pcie-designware.h | 1 +
> 2 files changed, 23 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/dwc/pcie-designware-host.c b/drivers/pci/dwc/pcie-designware-host.c
> index 5ba334938b52..be2b2762c944 100644
> --- a/drivers/pci/dwc/pcie-designware-host.c
> +++ b/drivers/pci/dwc/pcie-designware-host.c
> @@ -92,6 +92,8 @@ void dw_pcie_msi_init(struct pcie_port *pp)
> (u32)(msi_target & 0xffffffff));
> dw_pcie_wr_own_conf(pp, PCIE_MSI_ADDR_HI, 4,
> (u32)(msi_target >> 32 & 0xffffffff));
> +
> + pp->msi_disabled = false;
> }
>
> static void dw_pcie_msi_clear_irq(struct pcie_port *pp, int irq)
> @@ -136,9 +138,11 @@ static void dw_pcie_msi_set_irq(struct pcie_port *pp, int irq)
> static int assign_irq(int no_irqs, struct msi_desc *desc, int *pos)
> {
> int irq, pos0, i;
> - struct pcie_port *pp;
> + struct pcie_port *pp = (struct pcie_port *)msi_desc_to_pci_sysdata(desc);
> +
> + if (pp->msi_disabled)
> + return -EINVAL;
>
> - pp = (struct pcie_port *)msi_desc_to_pci_sysdata(desc);
> pos0 = bitmap_find_free_region(pp->msi_irq_in_use, MAX_MSI_IRQS,
> order_base_2(no_irqs));
> if (pos0 < 0)
> @@ -410,6 +414,22 @@ int dw_pcie_host_init(struct pcie_port *pp)
> goto error;
> }
>
> + /*
> + * The DWC host does not support legacy PCI IRQs and MSIs at the same
> + * time, so we need to fall back to using only legacy IRQs if there is
> + * a chance that multiple devices with differing MSI capabilities are
> + * connected to the host. The only configuration where MSIs can be
> + * safely used is when the device below the host bridge is not a bridge,
> + * i.e. the only device connected to this host.
> + */
> + child = list_first_entry(&bus->children, struct pci_bus, node);
> + if (!list_empty(&child->devices)) {
> + struct pci_dev *dev = list_first_entry(&child->devices,
> + struct pci_dev, bus_list);
> + if (pci_is_bridge(dev))
> + pp->msi_disabled = true;
> + }
> +
> if (pp->ops->scan_bus)
> pp->ops->scan_bus(pp);
>
> diff --git a/drivers/pci/dwc/pcie-designware.h b/drivers/pci/dwc/pcie-designware.h
> index cd3b8713fe50..741bc31f8947 100644
> --- a/drivers/pci/dwc/pcie-designware.h
> +++ b/drivers/pci/dwc/pcie-designware.h
> @@ -140,6 +140,7 @@ struct pcie_port {
> struct irq_domain *irq_domain;
> unsigned long msi_data;
> DECLARE_BITMAP(msi_irq_in_use, MAX_MSI_IRQS);
> + bool msi_disabled;
> };
>
> struct dw_pcie_ops {
> --
> 2.11.0
>
Lucas,
Legacy interrupts are still not firing with this.
Tim
