[PATCH] cxl: Ignore CAPI adapters misplaced in switched slots

[Ian Munsie]

Thanks Philippe - this looks like a decent solution to the problem (and
I intend to use this for the upcoming cx4 support as well).

Acked-by: Ian Munsie <imunsie at au1.ibm.com>

Excerpts from Philippe Bergheaud's message of 2016-06-30 13:45:37 +0200:
> One should not attempt to switch a PHB into CAPI mode if there is
> a switch between the PHB and the adapter. This patch modifies the
> cxl driver to ignore CAPI adapters misplaced in switched slots.
> 
> Signed-off-by: Philippe Bergheaud <felix at linux.vnet.ibm.com>
> ---
> This patch fixes Bz 142217.
> 
>  drivers/misc/cxl/pci.c | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/drivers/misc/cxl/pci.c b/drivers/misc/cxl/pci.c
> index a08fcc8..2f978ed 100644
> --- a/drivers/misc/cxl/pci.c
> +++ b/drivers/misc/cxl/pci.c
> @@ -1280,6 +1280,30 @@ static void cxl_pci_remove_adapter(struct cxl *adapter)
>      device_unregister(&adapter->dev);
>  }
>  
> +#define CXL_MAX_PCIEX_PARENT 2
> +
> +static int cxl_slot_is_switched(struct pci_dev *dev)
> +{
> +    struct device_node *np;
> +    int depth = 0;
> +    const __be32 *prop;
> +
> +    if (!(np = pci_device_to_OF_node(dev))) {
> +        pr_err("cxl: np = NULL\n");
> +        return -ENODEV;
> +    }
> +    of_node_get(np);
> +    while (np) {
> +        np = of_get_next_parent(np);
> +        prop = of_get_property(np, "device_type", NULL);
> +        if (!prop || strcmp((char *)prop, "pciex"))
> +            break;
> +        depth++;
> +    }
> +    of_node_put(np);
> +    return (depth > CXL_MAX_PCIEX_PARENT);
> +}
> +
>  static int cxl_probe(struct pci_dev *dev, const struct pci_device_id *id)
>  {
>      struct cxl *adapter;
> @@ -1291,6 +1315,11 @@ static int cxl_probe(struct pci_dev *dev, const struct pci_device_id *id)
>          return -ENODEV;
>      }
>  
> +    if (cxl_slot_is_switched(dev)) {
> +        dev_dbg(&dev->dev, "cxl_init_adapter: Ignoring switched slot device\n");
> +        return -ENODEV;
> +    }
> +
>      if (cxl_verbose)
>          dump_cxl_config_space(dev);
>