This series refactors the way CPU IDs are retrieved from the device tree.
Usually, there is a for loop that goes over every single CPU that can be avoided. This also reduces the amount of NULL pointer checks in drivers. I have abstracted away that loop and introduced a new function (of_cpu_node_to_id) for this.
This patchset is a subset of [1], where I removed content and patches relevant to hyper-threaded cores for DT. Based on the discussion, the code refactor is still useful, hence this patchset.
Changes since v1 [2]: - Rebased on top of the latest mainline. - Addressed Krzysztof Kozlowski's comments -- Hopefully :-) - Addressed Jonathan Cameron's comments.
[1] https://lore.kernel.org/all/20250512080715.82-1-alireza.sanaee@huawei.com/ [2] https://lore.kernel.org/all/20250707150414.620-1-alireza.sanaee@huawei.com/
Alireza Sanaee (5): of: add infra for finding CPU id from phandle arch_topology: update CPU map to use the new API coresight: cti: Use of_cpu_phandle_to_id for grabbing CPU id coresight: Use of_cpu_phandle_to_id for grabbing CPU id perf/arm-dsu: refactor cpu id retrieval via new API of_cpu_phandle_to_id
drivers/base/arch_topology.c | 16 ++++---- .../coresight/coresight-cti-platform.c | 14 +------ .../hwtracing/coresight/coresight-platform.c | 15 +------ drivers/of/cpu.c | 40 +++++++++++++++++++ drivers/perf/arm_dsu_pmu.c | 8 +--- include/linux/of.h | 9 +++++ 6 files changed, 61 insertions(+), 41 deletions(-)
Get CPU id from phandle. Many drivers get do this by getting hold of CPU node first through a phandle and then find the CPU ID using the relevant function. This commit encapsulates cpu node finding and improves readability.
The API interface requires two parameters, 1) node, 2) pointer to pointer of CPU node, 3) cpu node index. API sets the pointer to the CPU node and allows the driver to play with the CPU itself, for logging purposes for instance.
Signed-off-by: Alireza Sanaee alireza.sanaee@huawei.com --- drivers/of/cpu.c | 40 ++++++++++++++++++++++++++++++++++++++++ include/linux/of.h | 9 +++++++++ 2 files changed, 49 insertions(+)
diff --git a/drivers/of/cpu.c b/drivers/of/cpu.c index 5214dc3d05ae..494d47470f94 100644 --- a/drivers/of/cpu.c +++ b/drivers/of/cpu.c @@ -173,6 +173,46 @@ int of_cpu_node_to_id(struct device_node *cpu_node) } EXPORT_SYMBOL(of_cpu_node_to_id);
+/** + * of_cpu_phandle_to_id: Get the logical CPU number for a given device_node + * + * @node: Pointer to the device_node containing CPU phandle. + * @cpu_np: Pointer to the device_node for CPU. + * @cpu_idx: The index of the CPU in the list of CPUs. + * + * Return: The logical CPU number of the given CPU device_node or -ENODEV if + * the CPU is not found, or if the node is NULL, it returns -1. On success, + * cpu_np will always point to the retrieved CPU device_node with refcount + * incremented, use of_node_put() on it when done. + */ +int of_cpu_phandle_to_id(const struct device_node *node, + struct device_node **cpu_np, + uint8_t cpu_idx) +{ + struct device_node *local_cpu_node; + int cpu; + + if (!node) + return -1; + + local_cpu_node = of_parse_phandle(node, "cpu", 0); + if (!local_cpu_node) + local_cpu_node = of_parse_phandle(node, "cpus", cpu_idx); + + if (!local_cpu_node) + return -ENODEV; + + cpu = of_cpu_node_to_id(local_cpu_node); + + if (cpu_np) + *cpu_np = local_cpu_node; + else + of_node_put(local_cpu_node); + + return cpu; +} +EXPORT_SYMBOL(of_cpu_phandle_to_id); + /** * of_get_cpu_state_node - Get CPU's idle state node at the given index * diff --git a/include/linux/of.h b/include/linux/of.h index a62154aeda1b..717e55065d99 100644 --- a/include/linux/of.h +++ b/include/linux/of.h @@ -365,6 +365,8 @@ extern const void *of_get_property(const struct device_node *node, extern struct device_node *of_get_cpu_node(int cpu, unsigned int *thread); extern struct device_node *of_cpu_device_node_get(int cpu); extern int of_cpu_node_to_id(struct device_node *np); +extern int of_cpu_phandle_to_id(const struct device_node *np, + struct device_node **cpu_np, uint8_t cpu_idx); extern struct device_node *of_get_next_cpu_node(struct device_node *prev); extern struct device_node *of_get_cpu_state_node(const struct device_node *cpu_node, int index); @@ -680,6 +682,13 @@ static inline int of_cpu_node_to_id(struct device_node *np) return -ENODEV; }
+static inline int of_cpu_phandle_to_id(const struct device_node *np, + struct device_node **cpu_np, + uint8_t cpu_idx) +{ + return -ENODEV; +} + static inline struct device_node *of_get_next_cpu_node(struct device_node *prev) { return NULL;
Cleans up the cpu-map generation using the created API.
Signed-off-by: Alireza Sanaee alireza.sanaee@huawei.com --- drivers/base/arch_topology.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c index 1037169abb45..ccc73bfae90d 100644 --- a/drivers/base/arch_topology.c +++ b/drivers/base/arch_topology.c @@ -473,19 +473,19 @@ static unsigned int max_smt_thread_num = 1; */ static int __init get_cpu_for_node(struct device_node *node) { + struct device_node *cpu_node; int cpu; - struct device_node *cpu_node __free(device_node) = - of_parse_phandle(node, "cpu", 0);
- if (!cpu_node) - return -1; - - cpu = of_cpu_node_to_id(cpu_node); - if (cpu >= 0) + cpu = of_cpu_phandle_to_id(node, &cpu_node, 0); + if (cpu >= 0) { topology_parse_cpu_capacity(cpu_node, cpu); - else + of_node_put(cpu_node); + } else if (cpu == -ENODEV) { pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n", cpu_node, cpumask_pr_args(cpu_possible_mask)); + of_node_put(cpu_node); + } else + return -1;
return cpu; }
Use the newly created API to grab CPU id.
Signed-off-by: Alireza Sanaee alireza.sanaee@huawei.com --- .../hwtracing/coresight/coresight-cti-platform.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti-platform.c b/drivers/hwtracing/coresight/coresight-cti-platform.c index d0ae10bf6128..e1dc559d54aa 100644 --- a/drivers/hwtracing/coresight/coresight-cti-platform.c +++ b/drivers/hwtracing/coresight/coresight-cti-platform.c @@ -41,20 +41,8 @@ */ static int of_cti_get_cpu_at_node(const struct device_node *node) { - int cpu; - struct device_node *dn; + int cpu = of_cpu_phandle_to_id(node, NULL, 0);
- if (node == NULL) - return -1; - - dn = of_parse_phandle(node, "cpu", 0); - /* CTI affinity defaults to no cpu */ - if (!dn) - return -1; - cpu = of_cpu_node_to_id(dn); - of_node_put(dn); - - /* No Affinity if no cpu nodes are found */ return (cpu < 0) ? -1 : cpu; }
Hi,
On Tue, 8 Jul 2025 at 16:16, Alireza Sanaee alireza.sanaee@huawei.com wrote:
Use the newly created API to grab CPU id.
Signed-off-by: Alireza Sanaee alireza.sanaee@huawei.com
.../hwtracing/coresight/coresight-cti-platform.c | 14 +------------- 1 file changed, 1 insertion(+), 13 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-cti-platform.c b/drivers/hwtracing/coresight/coresight-cti-platform.c index d0ae10bf6128..e1dc559d54aa 100644 --- a/drivers/hwtracing/coresight/coresight-cti-platform.c +++ b/drivers/hwtracing/coresight/coresight-cti-platform.c @@ -41,20 +41,8 @@ */ static int of_cti_get_cpu_at_node(const struct device_node *node) {
int cpu;struct device_node *dn;
int cpu = of_cpu_phandle_to_id(node, NULL, 0);
if (node == NULL)return -1;dn = of_parse_phandle(node, "cpu", 0);/* CTI affinity defaults to no cpu */if (!dn)return -1;cpu = of_cpu_node_to_id(dn);of_node_put(dn);/* No Affinity if no cpu nodes are found */
Leave the above comment in place.
return (cpu < 0) ? -1 : cpu;}
-- 2.43.0
With that
Reviewed-by: Mike Leach mike.leach@linro.org
Use the newly created API to grab CPU id.
Signed-off-by: Alireza Sanaee alireza.sanaee@huawei.com --- drivers/hwtracing/coresight/coresight-platform.c | 15 +-------------- 1 file changed, 1 insertion(+), 14 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c index 0db64c5f4995..95d46ea08936 100644 --- a/drivers/hwtracing/coresight/coresight-platform.c +++ b/drivers/hwtracing/coresight/coresight-platform.c @@ -167,20 +167,7 @@ of_coresight_get_output_ports_node(const struct device_node *node)
static int of_coresight_get_cpu(struct device *dev) { - int cpu; - struct device_node *dn; - - if (!dev->of_node) - return -ENODEV; - - dn = of_parse_phandle(dev->of_node, "cpu", 0); - if (!dn) - return -ENODEV; - - cpu = of_cpu_node_to_id(dn); - of_node_put(dn); - - return cpu; + return of_cpu_phandle_to_id(dev->of_node, NULL, 0); }
/*
Update arm-dsu to use the new API, where both "cpus" and "cpu" properties are supported.
Signed-off-by: Alireza Sanaee alireza.sanaee@huawei.com --- drivers/perf/arm_dsu_pmu.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-)
diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c index cb4fb59fe04b..1014b92c0fd2 100644 --- a/drivers/perf/arm_dsu_pmu.c +++ b/drivers/perf/arm_dsu_pmu.c @@ -591,17 +591,13 @@ static struct dsu_pmu *dsu_pmu_alloc(struct platform_device *pdev) static int dsu_pmu_dt_get_cpus(struct device *dev, cpumask_t *mask) { int i = 0, n, cpu; - struct device_node *cpu_node;
n = of_count_phandle_with_args(dev->of_node, "cpus", NULL); if (n <= 0) return -ENODEV; + for (; i < n; i++) { - cpu_node = of_parse_phandle(dev->of_node, "cpus", i); - if (!cpu_node) - break; - cpu = of_cpu_node_to_id(cpu_node); - of_node_put(cpu_node); + cpu = of_cpu_phandle_to_id(dev->of_node, NULL, i); /* * We have to ignore the failures here and continue scanning * the list to handle cases where the nr_cpus could be capped
-
Alireza Sanaee -
Mike Leach