[Skiboot] [PATCH v2] hw/phb4: Tune GPU direct performance on witherspoon in PCI mode

[Oliver O'Halloran]

On Wed, Mar 25, 2020 at 4:51 AM Frederic Barrat <fbarrat at linux.ibm.com> wrote:
>
> +
> +static void witherspoon_pci_probe_complete(void)
> +{
> +       struct pci_device *dev;
> +       struct phb *phb;
> +       struct phb4 *p;
> +
> +       /*
> +        * Reallocate dma engines between stacks in PEC2 if a Mellanox
> +        * card is found on the shared slot, as it is required to get
> +        * good GPU direct performance.
> +        */
> +       for_each_phb(phb) {
> +               p = phb_to_phb4(phb);
> +               if (p->index != 3)
> +                       continue;

I think you need to check phb->type == phb_type_pcie_v4 before dereferencing p.

> +               dev = pci_walk_dev(phb, NULL, check_mlx_cards, NULL);
> +               if (dev)
> +                       phb4_pec2_dma_engine_realloc(p);
> +       }
> +}