Hi Mika,
On Wed, Dec 07, 2022 at 10:41:05AM +0200, Mika Westerberg wrote:
> Only Root Ports and Event Collectors use MSI for AER. PCIe Switch ports
> or endpoints on the other hand only send messages (that get collected by
> the former). For this reason do not require PCIe switch ports and
> endpoints to use interrupt if they support AER.
>
> This allows portdrv to attach PCIe switch ports of Intel DG1 and DG2
> discrete graphics cards. These do not declare MSI or legacy interrupts.
Help me understand more about this situation. I guess we want portdrv
to attach not to a GPU itself, but to a switch port on the card that
*leads* to the GPU?
>From the patch, it looks like the only PCIe port service this switch
port advertises is AER (not PME, DPC, hotplug, etc), and it doesn't
have MSI or MSI-X.
So aerdriver should be able to register for PCIE_PORT_SERVICE_AER, but
aer_probe() ignores everything except Root Ports and RCECs. What's
the benefit then? I must be missing something.
Bjorn
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
> ---
> Changes from v1:
>
> * Updated commit message to be more specific on which hardware this is
> needed.
>
> drivers/pci/pcie/portdrv_core.c | 15 ++++++++++++++-
> 1 file changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 1ac7fec47d6f..1b1c386e50c4 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -164,7 +164,7 @@ static int pcie_port_enable_irq_vec(struct pci_dev *dev, int *irqs, int mask)
> */
> static int pcie_init_service_irqs(struct pci_dev *dev, int *irqs, int mask)
> {
> - int ret, i;
> + int ret, i, type;
>
> for (i = 0; i < PCIE_PORT_DEVICE_MAXSERVICES; i++)
> irqs[i] = -1;
> @@ -177,6 +177,19 @@ static int pcie_init_service_irqs(struct pci_dev *dev, int *irqs, int mask)
> if ((mask & PCIE_PORT_SERVICE_PME) && pcie_pme_no_msi())
> goto legacy_irq;
>
> + /*
> + * Only root ports and event collectors use MSI for errors. Endpoints,
> + * switch ports send messages to them but don't use MSI for that (PCIe
> + * 5.0 sec 6.2.3.2).
> + */
> + type = pci_pcie_type(dev);
> + if ((mask & PCIE_PORT_SERVICE_AER) &&
> + type != PCI_EXP_TYPE_ROOT_PORT && type != PCI_EXP_TYPE_RC_EC)
> + mask &= ~PCIE_PORT_SERVICE_AER;
> +
> + if (!mask)
> + return 0;
> +
> /* Try to use MSI-X or MSI if supported */
> if (pcie_port_enable_irq_vec(dev, irqs, mask) == 0)
> return 0;
> --
> 2.35.1
>
