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

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Message-ID: <20220622154658.zehszxfe5eil3aq5@bogus>
Date:   Wed, 22 Jun 2022 16:46:58 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Ionela Voinescu <ionela.voinescu@....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>,
        Sudeep Holla <sudeep.holla@....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

On Wed, Jun 22, 2022 at 04:06:29PM +0100, Ionela Voinescu wrote:
> 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?
>

You are absolutely correct. For some reason when I wrote this patch I
read the line above as depth++ instead of depth + 1. I was searching
for that now reading your reply just to realise that I misread it.

Thanks for catching this.

-- 
Regards,
Sudeep