linux-kernel - Re: [PATCH v4 20/20] arch_topology: Warn that topology for nested clusters is not supported

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Date:   Wed, 22 Jun 2022 16:06:29 +0100
From:   Ionela Voinescu <ionela.voinescu@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-kernel@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Atish Patra <atishp@...shpatra.org>,
        Atish Patra <atishp@...osinc.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Qing Wang <wangqing@...o.com>,
        Rob Herring <robh+dt@...nel.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Pierre Gondois <pierre.gondois@....com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-riscv@...ts.infradead.org
Subject: Re: [PATCH v4 20/20] arch_topology: Warn that topology for nested
 clusters is not supported

Hi,

I just noticed this in a quick test.

On Tuesday 21 Jun 2022 at 20:20:34 (+0100), Sudeep Holla wrote:
> We don't support the topology for clusters of CPU clusters while the
> DT and ACPI bindings theoritcally support the same. Just warn about the
> same so that it is clear to the users of arch_topology that the nested
> clusters are not yet supported.
> 
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/base/arch_topology.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index ed1cb64a95aa..1c5fa7bbbd00 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -567,6 +567,8 @@ static int __init parse_cluster(struct device_node *cluster, int package_id,
>  		if (c) {
>  			leaf = false;
>  			ret = parse_cluster(c, package_id, i, depth + 1);
> +			if (depth > 1)
> +				pr_warn("Topology for clusters of clusters not yet supported\n");

I think the check should be for (depth > 0) or (depth >= 1).

We end up having depth = 2 when we have

cluster 0 {
	//depth is 0
	cluster 0 {
		//depth is 1
		cluster0 {
			//depth is 2
...

I suppose we should warn about nested clusters from depth 1, right?

Thanks,
Ionela.

>  			of_node_put(c);
>  			if (ret != 0)
>  				return ret;
> -- 
> 2.36.1
>