linux-kernel - Re: [PATCH v2 1/2] of: base: add support to find the level of the last cache

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Date:   Fri, 13 Jan 2017 20:45:55 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Tan Xiaojun <tanxiaojun@...wei.com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2 1/2] of: base: add support to find the level of the
 last cache

On Thu, Jan 12, 2017 at 12:29 PM, Sudeep Holla <sudeep.holla@....com> wrote:
> It is useful to have helper function just to get the number of cache
> levels for a given logical cpu. We can obtain the same by just checking
> the level at which the last cache is present. This patch adds support
> to find the level of the last cache for a given cpu.
>
> It will be used on ARM64 platform where the device tree provides the
> information for the additional non-architected/transparent/external
> last level caches that are not integrated with the processors.
>
> Suggested-by: Rob Herring <robh+dt@...nel.org>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> ---
>  drivers/of/base.c  | 27 +++++++++++++++++++++++++++
>  include/linux/of.h |  1 +
>  2 files changed, 28 insertions(+)
>
> v1->v2:
>         - Moved to using "cache-level" in the last level cache instead
>           of counting through all the nodes as suggested by Rob
>
> diff --git a/drivers/of/base.c b/drivers/of/base.c
> index d4bea3c797d6..c1128a077aea 100644
> --- a/drivers/of/base.c
> +++ b/drivers/of/base.c
> @@ -25,6 +25,7 @@
>  #include <linux/cpu.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/of_graph.h>
>  #include <linux/spinlock.h>
>  #include <linux/slab.h>
> @@ -2268,6 +2269,32 @@ struct device_node *of_find_next_cache_node(const struct device_node *np)
>  }
>
>  /**
> + * of_find_last_cache_level - Find the level at which the last cache is
> + *             present for the given logical cpu
> + *
> + * @cpu: cpu number(logical index) for which the last cache level is needed
> + *
> + * Returns the the level at which the last cache is present. It is exactly
> + * same as  the total number of cache levels for the given logical cpu.
> + */
> +int of_find_last_cache_level(unsigned int cpu)
> +{
> +       int cache_level = 0;
> +       struct device_node *prev = NULL, *np = of_cpu_device_node_get(cpu);
> +
> +       while (np) {
> +               prev = np;
> +               of_node_put(np);
> +               np = of_find_next_cache_node(np);
> +       }
> +
> +       if (prev)

Probably don't need this check. Otherwise,

Acked-by: Rob Herring <robh@...nel.org>

> +               of_property_read_u32(prev, "cache-level", &cache_level);
> +
> +       return cache_level;
> +}
> +
> +/**
>   * of_graph_parse_endpoint() - parse common endpoint node properties
>   * @node: pointer to endpoint device_node
>   * @endpoint: pointer to the OF endpoint data structure
> diff --git a/include/linux/of.h b/include/linux/of.h
> index d72f01009297..21e6323de0f3 100644
> --- a/include/linux/of.h
> +++ b/include/linux/of.h
> @@ -280,6 +280,7 @@ extern struct device_node *of_get_child_by_name(const struct device_node *node,
>
>  /* cache lookup */
>  extern struct device_node *of_find_next_cache_node(const struct device_node *);
> +extern int of_find_last_cache_level(unsigned int cpu);
>  extern struct device_node *of_find_node_with_property(
>         struct device_node *from, const char *prop_name);
>
> --
> 2.7.4
>