linux-kernel - Re: [PATCH 1/2] drivers: psci: remove cluster terminology and dependency on physical_package

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Message-ID: <20180109173451.GB17222@red-moon>
Date:   Tue, 9 Jan 2018 17:34:51 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Jeremy Linton <jeremy.linton@....com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH 1/2] drivers: psci: remove cluster terminology and
 dependency on physical_package_id

On Tue, Jan 09, 2018 at 04:49:27PM +0000, Sudeep Holla wrote:
> Since the definition of the term "cluster" is not well defined in the
> architecture, we should avoid using it. Also the physical package id
> is currently mapped to so called "clusters" in ARM/ARM64 platforms which
> is already argumentative.

I think we should describe why the PSCI checker uses the physical
package id (ie because it is likely that power domains map to "clusters"
- so physical package id *current* boundaries, it is trying to test
"cluster" idle states) but I can easily rework the log before sending it
upstream.

I will send it upstream for the next cycle along with patch (2), or
if you prefer to send it yourself:

Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>

Thanks for putting it together,
Lorenzo

> This patch removes the dependency on physical_package_id from the topology
> in this PSCI checker. Also it replaces all the occurences of clusters to
> cpu_groups which is derived from core_sibling_mask and may not directly
> map to physical "cluster".
> 
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/firmware/psci_checker.c | 46 ++++++++++++++++++++---------------------
>  1 file changed, 22 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/firmware/psci_checker.c b/drivers/firmware/psci_checker.c
> index f3f4f810e5df..bb1c068bff19 100644
> --- a/drivers/firmware/psci_checker.c
> +++ b/drivers/firmware/psci_checker.c
> @@ -77,8 +77,8 @@ static int psci_ops_check(void)
>  	return 0;
>  }
>  
> -static int find_clusters(const struct cpumask *cpus,
> -			 const struct cpumask **clusters)
> +static int find_cpu_groups(const struct cpumask *cpus,
> +			   const struct cpumask **cpu_groups)
>  {
>  	unsigned int nb = 0;
>  	cpumask_var_t tmp;
> @@ -88,11 +88,11 @@ static int find_clusters(const struct cpumask *cpus,
>  	cpumask_copy(tmp, cpus);
>  
>  	while (!cpumask_empty(tmp)) {
> -		const struct cpumask *cluster =
> +		const struct cpumask *cpu_group =
>  			topology_core_cpumask(cpumask_any(tmp));
>  
> -		clusters[nb++] = cluster;
> -		cpumask_andnot(tmp, tmp, cluster);
> +		cpu_groups[nb++] = cpu_group;
> +		cpumask_andnot(tmp, tmp, cpu_group);
>  	}
>  
>  	free_cpumask_var(tmp);
> @@ -170,24 +170,24 @@ static int hotplug_tests(void)
>  {
>  	int err;
>  	cpumask_var_t offlined_cpus;
> -	int i, nb_cluster;
> -	const struct cpumask **clusters;
> +	int i, nb_cpu_group;
> +	const struct cpumask **cpu_groups;
>  	char *page_buf;
>  
>  	err = -ENOMEM;
>  	if (!alloc_cpumask_var(&offlined_cpus, GFP_KERNEL))
>  		return err;
> -	/* We may have up to nb_available_cpus clusters. */
> -	clusters = kmalloc_array(nb_available_cpus, sizeof(*clusters),
> -				 GFP_KERNEL);
> -	if (!clusters)
> +	/* We may have up to nb_available_cpus cpu_groups. */
> +	cpu_groups = kmalloc_array(nb_available_cpus, sizeof(*cpu_groups),
> +				   GFP_KERNEL);
> +	if (!cpu_groups)
>  		goto out_free_cpus;
>  	page_buf = (char *)__get_free_page(GFP_KERNEL);
>  	if (!page_buf)
> -		goto out_free_clusters;
> +		goto out_free_cpu_groups;
>  
>  	err = 0;
> -	nb_cluster = find_clusters(cpu_online_mask, clusters);
> +	nb_cpu_group = find_cpu_groups(cpu_online_mask, cpu_groups);
>  
>  	/*
>  	 * Of course the last CPU cannot be powered down and cpu_down() should
> @@ -197,24 +197,22 @@ static int hotplug_tests(void)
>  	err += down_and_up_cpus(cpu_online_mask, offlined_cpus);
>  
>  	/*
> -	 * Take down CPUs by cluster this time. When the last CPU is turned
> -	 * off, the cluster itself should shut down.
> +	 * Take down CPUs by cpu group this time. When the last CPU is turned
> +	 * off, the cpu group itself should shut down.
>  	 */
> -	for (i = 0; i < nb_cluster; ++i) {
> -		int cluster_id =
> -			topology_physical_package_id(cpumask_any(clusters[i]));
> +	for (i = 0; i < nb_cpu_group; ++i) {
>  		ssize_t len = cpumap_print_to_pagebuf(true, page_buf,
> -						      clusters[i]);
> +						      cpu_groups[i]);
>  		/* Remove trailing newline. */
>  		page_buf[len - 1] = '\0';
> -		pr_info("Trying to turn off and on again cluster %d "
> -			"(CPUs %s)\n", cluster_id, page_buf);
> -		err += down_and_up_cpus(clusters[i], offlined_cpus);
> +		pr_info("Trying to turn off and on again group %d (CPUs %s)\n",
> +			i, page_buf);
> +		err += down_and_up_cpus(cpu_groups[i], offlined_cpus);
>  	}
>  
>  	free_page((unsigned long)page_buf);
> -out_free_clusters:
> -	kfree(clusters);
> +out_free_cpu_groups:
> +	kfree(cpu_groups);
>  out_free_cpus:
>  	free_cpumask_var(offlined_cpus);
>  	return err;
> -- 
> 2.7.4
>