Re: [PATCH 1/2] arch_topology: support for describing cache topology from DT

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Apr 21, 2022 at 07:55:57AM -0700, Qing Wang wrote:
> From: Wang Qing <wangqing@vivo.com>
> 
> When ACPI is not enabled, we can get cache topolopy from DT like:
> *		cpu0: cpu@000 {
> *			next-level-cache = <&L2_1>;
> *			L2_1: l2-cache {
> * 				compatible = "cache";
> *				next-level-cache = <&L3_1>;
> * 			};
> *			L3_1: l3-cache {
> * 				compatible = "cache";
> * 			};
> *		};
> *
> *		cpu1: cpu@001 {
> *			next-level-cache = <&L2_1>;
> *		};
> *		...
> *		};
> cache_topology hold the pointer describing "next-level-cache", 
> it can describe the cache topology of every level.
> 
> Signed-off-by: Wang Qing <wangqing@vivo.com>
> ---
>  drivers/base/arch_topology.c  | 47 ++++++++++++++++++++++++++++++++++-
>  include/linux/arch_topology.h |  3 +++
>  2 files changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 1d6636ebaac5..46e84ce2ec0c 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -480,8 +480,10 @@ static int __init get_cpu_for_node(struct device_node *node)
>  		return -1;
>  
>  	cpu = of_cpu_node_to_id(cpu_node);
> -	if (cpu >= 0)
> +	if (cpu >= 0) {
>  		topology_parse_cpu_capacity(cpu_node, cpu);
> +		topology_parse_cpu_caches(cpu_node, cpu);
> +	}
>  	else
>  		pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
>  			cpu_node, cpumask_pr_args(cpu_possible_mask));
> @@ -647,6 +649,49 @@ static int __init parse_dt_topology(void)
>  }
>  #endif
>  
> +/*
> + * cpu cache topology table
> + */
> +#define MAX_CACHE_LEVEL 7
> +staic struct device_node *cache_topology[NR_CPUS][MAX_CACHE_LEVEL];
> +
> +void topology_parse_cpu_caches(struct device_node *cpu_node, int cpu)
> +{
> +	struct device_node *node_cache = cpu_node;
> +	int level = 0;
> +
> +	while (level < MAX_CACHE_LEVEL) {
> +		node_cache = of_parse_phandle(node_cache, "next-level-cache", 0);
> +		if (!node_cache)
> +			break;
> +
> +		cache_topology[cpu][level++] = node_cache;
> +	}
> +}
> +
> +/*
> + * find the maximum level shared cache under giving mask
> + */
> +void find_max_sub_sc(const struct cpumask *giving_mask, int cpu,
> +					  struct cpumask *sc_mask)

This is not a good global function name.  No one will know what this
means when they read it.  Please make it make more sense.

thanks,

greg k-h