On Fri, Jun 25, 2021 at 06:36:48PM +1000, Gavin Shan wrote:
> On 6/25/21 5:06 PM, Andrew Jones wrote:
> > On Fri, Jun 25, 2021 at 09:02:17AM +0200, Andrew Jones wrote:
> > > On Fri, Jun 25, 2021 at 01:23:38PM +0800, Gavin Shan wrote:
> > > > The empty memory nodes, where no memory resides in, are allowed.
> > > > For these empty memory nodes, the 'len' of 'reg' property is zero.
> > > > The NUMA node IDs are still valid and parsed, but memory can be
> > > > added to them through hotplug afterwards. I finds difficulty to
> > > > get where it's properly documented.
> > > >
> > > > So lets add note to empty memory nodes in the NUMA binding doc.
> > > >
> > > > Signed-off-by: Gavin Shan <gshan@xxxxxxxxxx>
> > > > ---
> > > > Documentation/devicetree/bindings/numa.txt | 4 ++++
> > > > 1 file changed, 4 insertions(+)
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/numa.txt b/Documentation/devicetree/bindings/numa.txt
> > > > index 21b35053ca5a..0fc882e44270 100644
> > > > --- a/Documentation/devicetree/bindings/numa.txt
> > > > +++ b/Documentation/devicetree/bindings/numa.txt
> > > > @@ -109,6 +109,10 @@ Example:
> > > > Dual socket system consists of 2 boards connected through ccn bus and
> > > > each board having one socket/soc of 8 cpus, memory and pci bus.
> > > > +Note that empty memory nodes, which no memory resides in, are allowed.
> > > > +The NUMA node IDs in these empty memory nodes are still valid, but
> > > > +memory can be added into them through hotplug afterwards.
> > >
> > > Please change the second sentence to:
> > >
> > > The NUMA node IDs in these empty memory nodes are still valid and
> > > memory may be added into them through hotplug afterwards.
> > >
> > > But, this doesn't look like the right place for this paragraph. You're
> > > adding the paragraph to the example section, but the example doesn't have
> > > any empty memory nodes.
> > >
> > > I think the paragraph should be added to section "2 - numa-node-id" and an
> >
> > Or maybe even create a new section for it.
> >
> > > example empty memory node should be provided. Also, the commit message
> > > talks about the length of 'reg' being zero, which is an important
> > > distinction which should also be documented.
> > >
>
> Drew, thanks for your comments. Yeah, it sounds sensible to create
> a new section for it and an example would be more helpful. Please
> check if below changes are fine to you. I probably need Randy's review
> again.
>
> I'm trying to avoid too many revisions for this sort of trivial patch,
> even though I already had. However, it's time frame for v5.14 and I'm
> pushing this to be merged during the cycle.
We must revise until we're satisfied... Also, I wouldn't call writing
specifications trivial.
>
> --- a/Documentation/devicetree/bindings/numa.txt
> +++ b/Documentation/devicetree/bindings/numa.txt
> @@ -103,7 +103,65 @@ Example:
> };
> ==============================================================================
> -4 - Example dts
> +4 - Empty memory node
nodes
> +==============================================================================
> +
> +Empty memory nodes, which no memory resides in, are allowed. The 'length'
> +field of 'reg' property is zero, but 'base-address' is dummy and invalid
is a dummy address and is invalid.
> +for these empty memory nodes.
Can drop this "for these empty memory nodes" that's clear from the
context.
> However, the NUMA node IDs and distance maps
> +for them are still valid, but memory may be added into them through hotplug
^ drop 'for them' ^ Again, this should be "and". "but" is a
contrastive conjunction. We want to express that the nodes are valid *and*
may have memory hotplugged later.
> +afterwards.
I'll just rewrite it:
Empty memory nodes, which no memory resides in, are allowed. The 'length'
field of the 'reg' property is zero, but the 'base-address' is a dummy
address and invalid. However, the NUMA node IDs and distance maps are
still valid and memory may be added into them through hotplug afterwards.
> +
> +Example:
> +
> + memory@0 {
> + device_type = "memory";
> + reg = <0x0 0x0 0x0 0x80000000>;
> + numa-node-id = <0>;
> + };
> +
> + memory@0x80000000 {
> + device_type = "memory";
> + reg = <0x0 0x80000000 0x0 0x80000000>;
> + numa-node-id = <1>;
> + };
> +
> + /* Empty memory node */
You should write how you've selected the dummy addresses for the empty
memory nodes, perhaps here in the /* Empty memory node */ comments or
above in the paragraph or both.
> + memory@0x100000000 {
> + device_type = "memory";
> + reg = <0x1 0x0 0x0 0x0>;
> + numa-node-id = <2>;
> + };
> +
> + /* Empty memory node */
> + memory@0x180000000 {
> + device_type = "memory";
> + reg = <0x1 0x80000000 0x0 0x0>;
> + numa-node-id = <3>;
> + };
> +
> + distance-map {
> + compatible = "numa-distance-map-v1";
> + distance-matrix = <0 0 10>,
> + <0 1 20>,
> + <0 2 40>,
> + <0 3 20>,
> + <1 0 20>,
> + <1 1 10>,
> + <1 2 20>,
> + <1 3 40>,
> + <2 0 40>,
> + <2 1 20>,
> + <2 2 10>,
> + <2 3 20>,
> + <3 0 20>,
> + <3 1 40>,
> + <3 2 20>,
> + <3 3 10>;
> + };
> +
> +==============================================================================
> +5 - Example dts
> ==============================================================================
> Dual socket system consists of 2 boards connected through ccn bus and
>
>
> Thanks,
> Gavin
>
>
Thanks,
drew
