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SubjectRe: [PATCH v3] perf: arm_dsu: Support DSU ACPI devices
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On 09/07/2020 12:02 PM, Will Deacon wrote:
> [+ Suzuki as I'd like his Ack on this]
>

Thanks Will !

> On Fri, Aug 14, 2020 at 05:39:40PM -0700, Tuan Phan wrote:
>> Add support for probing device from ACPI node.
>> Each DSU ACPI node and its associated cpus are inside a cluster node.
>>
>> Signed-off-by: Tuan Phan <tuanphan@os.amperecomputing.com>
>> ---
>> Changes in v3:
>> - Based on the latest ARM ACPI binding at: https://developer.arm.com/documentation/den0093/c/
>>
>> Changes in v2:
>> - Removed IRQF_SHARED.
>> - Fixed ACPI runtime detection.
>>
>> drivers/perf/arm_dsu_pmu.c | 68 ++++++++++++++++++++++++++++++++++++++++------
>> 1 file changed, 60 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/perf/arm_dsu_pmu.c b/drivers/perf/arm_dsu_pmu.c
>> index 96ed93c..4be355d 100644
>> --- a/drivers/perf/arm_dsu_pmu.c
>> +++ b/drivers/perf/arm_dsu_pmu.c
>> @@ -11,6 +11,7 @@
>> #define DRVNAME PMUNAME "_pmu"
>> #define pr_fmt(fmt) DRVNAME ": " fmt
>>
>> +#include <linux/acpi.h>
>> #include <linux/bitmap.h>
>> #include <linux/bitops.h>
>> #include <linux/bug.h>
>> @@ -603,18 +604,21 @@ static struct dsu_pmu *dsu_pmu_alloc(struct platform_device *pdev)
>> }
>>
>> /**
>> - * dsu_pmu_dt_get_cpus: Get the list of CPUs in the cluster.
>> + * dsu_pmu_dt_get_cpus: Get the list of CPUs in the cluster
>> + * from device tree.
>> */
>> -static int dsu_pmu_dt_get_cpus(struct device_node *dev, cpumask_t *mask)
>> +static int dsu_pmu_dt_get_cpus(struct platform_device *pdev)
>> {
>> int i = 0, n, cpu;
>> struct device_node *cpu_node;
>> + struct dsu_pmu *dsu_pmu =
>> + (struct dsu_pmu *) platform_get_drvdata(pdev);
>>
>> - n = of_count_phandle_with_args(dev, "cpus", NULL);
>> + n = of_count_phandle_with_args(pdev->dev.of_node, "cpus", NULL);
>> if (n <= 0)
>> return -ENODEV;
>> for (; i < n; i++) {
>> - cpu_node = of_parse_phandle(dev, "cpus", i);
>> + cpu_node = of_parse_phandle(pdev->dev.of_node, "cpus", i);
>> if (!cpu_node)
>> break;
>> cpu = of_cpu_node_to_id(cpu_node);
>> @@ -626,11 +630,51 @@ static int dsu_pmu_dt_get_cpus(struct device_node *dev, cpumask_t *mask)
>> */
>> if (cpu < 0)
>> continue;
>> - cpumask_set_cpu(cpu, mask);
>> + cpumask_set_cpu(cpu, &dsu_pmu->associated_cpus);
>> }
>> return 0;
>> }
>>
>> +/**
>> + * dsu_pmu_acpi_get_cpus: Get the list of CPUs in the cluster
>> + * from ACPI.
>> + */
>> +static int dsu_pmu_acpi_get_cpus(struct platform_device *pdev)
>> +{
>> + int cpu;
>> + struct dsu_pmu *dsu_pmu = (struct dsu_pmu *) platform_get_drvdata(pdev);
>> +
>> + /*
>> + * A dsu pmu node is inside a cluster parent node along with cpu nodes.
>> + * We need to find out all cpus that have the same parent with this pmu.
>> + */
>> + for_each_possible_cpu(cpu) {
>> + struct acpi_device *acpi_dev = ACPI_COMPANION(get_cpu_device(cpu));

minor nit: Please could we split this into :

struct acpi_device *acpi_dev;
struct device *cpu_dev = get_cpu_device(cpu);

if (!cpu_dev)
continue;

acpi_dev = ACPI_COMPANION(cpu_dev); ...

So that we are explicitly clear that we don't end up in NULL pointer
dereferences (ACPI_COMPANION() is safe btw). Otherwise, with Will's
comments addressed, looks fine to me.

Appreciate a Cc in the next posting.

Suzuki

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