linux-kernel - Re: [PATCH V2] arch_topology: support parsing cluster

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Date:   Thu, 12 May 2022 12:58:50 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Qing Wang <wangqing@...o.com>, Sudeep Holla <sudeep.holla@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] arch_topology: support parsing cluster_id from DT

On 11/05/2022 11:52, Qing Wang wrote:
> From: Wang Qing <wangqing@...o.com>

[...]

> @@ -582,7 +594,8 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
>  			}
>  
>  			if (leaf) {
> -				ret = parse_core(c, package_id, core_id++);
> +				ret = parse_core(c, package_id, (depth == 2)?cluster_id : -1,
> +					       core_id++);
>  			} else {
>  				pr_err("%pOF: Non-leaf cluster with core %s\n",
>  				       cluster, name);
> @@ -599,9 +612,6 @@ static int __init parse_cluster(struct device_node *cluster, int depth)
>  	if (leaf && !has_cores)
>  		pr_warn("%pOF: empty cluster\n", cluster);
>  
> -	if (leaf)
> -		package_id++;
> -
>  	return 0;
>  }

The issue I mentioned under
https://lkml.kernel.org/r/bd746cf0-0fdd-1ee6-d394-67fffb5d9b58@arm.com
still exists.

Btw, I recommend the following test strategy.

(A) Create a set of dts files which represent today's topologies in DT:

  (1) 8 CPUs flat (Arm DynamIQ single DSU)

  (2) 2 groups of 4 CPUs (e.g. hikey 960) (which covers Phantom* domain)

  (3) your QC SM8450 Armv9 tri-gear (4-3-1) DynamIQ single DSU w/ shared
      L2 btwn CPU0-1 and CPU2-3.
  ...

 * used in Android

(B) Compile dtb's

  dtc -I dts -O dtb -o foo.dtb foo.dts


(C) Run them under qemu w/ and w/o CONFIG_SCHED_CLUSTER and check:

  sudo qemu-system-aarch64 ... -dtb foo.dtb

  (1) sched domains:

      cat /sys/kernel/debug/sched/domains/cpu*/domain*/name

  (2) sched flags:

      cat /sys/kernel/debug/sched/domains/cpu*/domain*/flags

  (3) cpumasks:

      cat /proc/schedstat | awk '{print $1 " " $2 }' | grep ^[cd]

You can even mention the test results in your patch so that people see
that you already covered them. This will speed up the review-process
enormously.