Re: [PATCH v2] PCI/portdrv: Do not require an interrupt for all AER capable ports

[Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>]

On 12/7/22 12:41 AM, 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.
> 
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

> ---
> 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;

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer