[Skiboot] [PATCH] hw/npu2.c: Add ibm, nvlink-speed device-tree property

[Alistair Popple]

Stewart,

We're going to change the values of the enum here so I'm going to resubmit this
patch. Thanks.

Regards,

Alistair

On Thu, 17 Aug 2017 06:12:47 PM Alistair Popple wrote:
> NVLink2 links can support multiple different speeds. However the device driver
> has no way of determining which speed was programmed so pass it down as a device
> tree property.
> 
> Signed-off-by: Alistair Popple <alistair at popple.id.au>
> ---
>  doc/device-tree/nvlink.rst | 7 ++++++-
>  hw/npu2.c                  | 8 ++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/doc/device-tree/nvlink.rst b/doc/device-tree/nvlink.rst
> index 6ce44e9..2876ca8 100644
> --- a/doc/device-tree/nvlink.rst
> +++ b/doc/device-tree/nvlink.rst
> @@ -105,7 +105,12 @@ Emulated PCI device bindings
>                          vendor-id = <0x1014>;
>                          ibm,gpu = <0x100002f7>; /* phandle pointing the associated GPU PCI device node */
>  			memory-region = <0x10000abc>; /* phandle pointing to the GPU memory */
> -			phandle = <0x100002fc>;
> +                        ibm,nvlink-speed = <0x1>;
> +
> +                ; Denotes the speed the link is running at:
> +                ; 0x0 == 20 Gbps, 0x1 == 25.00000 Gbps, 0x2 = 25.78125 Gbps
> +
> +                        phandle = <0x100002fc>;
>                  };
>  
>                  pci at 1 {
> diff --git a/hw/npu2.c b/hw/npu2.c
> index 74e3325..cab7347 100644
> --- a/hw/npu2.c
> +++ b/hw/npu2.c
> @@ -683,6 +683,14 @@ static int npu2_dn_fixup(struct phb *phb,
>  	npu2_dn_fixup_gmb(pd->dn, dev);
>  	dt_add_property_cells(pd->dn, "ibm,nvlink", dev->dt_node->phandle);
>  
> +	/* NVLink supports multiple speeds and device drivers need to know what
> +	 * speed has been set by firmware. The speed is actually controlled by
> +	 * Hostboot, so until we get a HDAT entry telling us what speed they
> +	 * programmed we will just hard code it here and hope it matches. If it
> +	 * doesn't it is always possible to manually override it when installing
> +	 * the device driver. */
> +	dt_add_property_cells(pd->dn, "ibm,nvlink-speed", 0x1);
> +
>  	/* NPU devices require a slot location to associate with GPUs */
>  	dev->slot_label = dt_prop_get_def(pd->dn, "ibm,slot-label", NULL);
>  	if (!dev->slot_label) {
>