Re: [PATCH 5/5] perf/arm_cspmu: Add devicetree support

[Robin Murphy <robin.murphy@xxxxxxx>]

On 2023-12-06 11:43 pm, Ilkka Koskinen wrote:
> Hi Robin,
>
> On Tue, 5 Dec 2023, Robin Murphy wrote:
> > Hook up devicetree probing support. For now let's hope that people
> > implement PMIIDR properly and we don't need an override mechanism.
> >
> > Signed-off-by: Robin Murphy <robin.murphy@xxxxxxx>
> > ---
> > drivers/perf/arm_cspmu/arm_cspmu.c | 71 +++++++++++++++++++++++-------
> > 1 file changed, 56 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c 
> > b/drivers/perf/arm_cspmu/arm_cspmu.c
> > index b64de4d800c7..80b5fc417ee3 100644
> > --- a/drivers/perf/arm_cspmu/arm_cspmu.c
> > +++ b/drivers/perf/arm_cspmu/arm_cspmu.c
> > @@ -27,6 +27,7 @@
> > #include <linux/io-64-nonatomic-lo-hi.h>
> > #include <linux/module.h>
> > #include <linux/mutex.h>
> > +#include <linux/of.h>
> > #include <linux/perf_event.h>
> > #include <linux/platform_device.h>
> >
> > @@ -309,6 +310,10 @@ static const char *arm_cspmu_get_name(const 
> > struct arm_cspmu *cspmu)
> >     static atomic_t pmu_idx[ACPI_APMT_NODE_TYPE_COUNT] = { 0 };
> >
> >     dev = cspmu->dev;
> > +    if (!has_acpi_companion(dev))
>
> Am I missing something since this doesn't work on top of v6.7-rc4?
> The problem I see is that has_acpi_companion() calls 
> is_acpi_device_node(), which compares whether
>
>      fwnode->ops == &acpi_device_fwnode_ops;
>
> However, the acpi/apmt code allocates fwnode by calling
> acpi_alloc_fwnode_static(), which assigns &acpi_static_fwnode_ops
> to ops.

Ah, I hadn't got as far as considering that has_acpi_companion() might 
only work for namespace devices, but it makes sense now that you point 
it out. I should have clarified that I don't have any suitable ACPI 
system to test this on, and have only been able to verify basic DT 
probing on an FPGA.

> I wonder though, if is_acpi_device_node() should check the static 
> variant too? :/

Thanks for the tip, I'll look into that and try to come up with 
something that works for a v2 (at worst there's always the traditional 
assumption that !dev->of_node implies ACPI)

Cheers,
Robin.

> Cheers, Ilkka
>
> > +        return devm_kasprintf(dev, GFP_KERNEL, PMUNAME "_%u",
> > +                      atomic_fetch_inc(&pmu_idx[0]));
> > +
> >     apmt_node = arm_cspmu_apmt_node(dev);
> >     pmu_type = apmt_node->type;
> >
> > @@ -406,7 +411,6 @@ static struct arm_cspmu_impl_match 
> > *arm_cspmu_impl_match_get(u32 pmiidr)
> > static int arm_cspmu_init_impl_ops(struct arm_cspmu *cspmu)
> > {
> >     int ret = 0;
> > -    struct acpi_apmt_node *apmt_node = arm_cspmu_apmt_node(cspmu->dev);
> >     struct arm_cspmu_impl_match *match;
> >
> >     /* Start with a default PMU implementation */
> > @@ -425,8 +429,12 @@ static int arm_cspmu_init_impl_ops(struct 
> > arm_cspmu *cspmu)
> >     };
> >
> >     /* Firmware may override implementer/product ID from PMIIDR */
> > -    if (apmt_node->impl_id)
> > -        cspmu->impl.pmiidr = apmt_node->impl_id;
> > +    if (has_acpi_companion(cspmu->dev)) {
> > +        struct acpi_apmt_node *apmt_node = 
> > arm_cspmu_apmt_node(cspmu->dev);
> > +
> > +        if (apmt_node->impl_id)
> > +            cspmu->impl.pmiidr = apmt_node->impl_id;
> > +    }
> >
> >     /* Find implementer specific attribute ops. */
> >     match = arm_cspmu_impl_match_get(cspmu->impl.pmiidr);
> > @@ -928,7 +936,6 @@ static void arm_cspmu_read(struct perf_event *event)
> >
> > static struct arm_cspmu *arm_cspmu_alloc(struct platform_device *pdev)
> > {
> > -    struct acpi_apmt_node *apmt_node;
> >     struct arm_cspmu *cspmu;
> >     struct device *dev = &pdev->dev;
> >
> > @@ -939,8 +946,13 @@ static struct arm_cspmu *arm_cspmu_alloc(struct 
> > platform_device *pdev)
> >     cspmu->dev = dev;
> >     platform_set_drvdata(pdev, cspmu);
> >
> > -    apmt_node = arm_cspmu_apmt_node(dev);
> > -    cspmu->has_atomic_dword = apmt_node->flags & ACPI_APMT_FLAGS_ATOMIC;
> > +    if (has_acpi_companion(dev)) {
> > +        struct acpi_apmt_node *apmt_node = arm_cspmu_apmt_node(dev);
> > +
> > +        cspmu->has_atomic_dword = apmt_node->flags & 
> > ACPI_APMT_FLAGS_ATOMIC;
> > +    } else {
> > +        cspmu->has_atomic_dword = device_property_read_bool(dev, 
> > "arm,64-bit-atomic");
> > +    }
> >
> >     return cspmu;
> > }
> > @@ -1133,11 +1145,6 @@ static int arm_cspmu_acpi_get_cpus(struct 
> > arm_cspmu *cspmu)
> >         }
> >     }
> >
> > -    if (cpumask_empty(&cspmu->associated_cpus)) {
> > -        dev_dbg(cspmu->dev, "No cpu associated with the PMU\n");
> > -        return -ENODEV;
> > -    }
> > -
> >     return 0;
> > }
> > #else
> > @@ -1147,9 +1154,36 @@ static int arm_cspmu_acpi_get_cpus(struct 
> > arm_cspmu *cspmu)
> > }
> > #endif
> >
> > +static int arm_cspmu_of_get_cpus(struct arm_cspmu *cspmu)
> > +{
> > +    struct of_phandle_iterator it;
> > +    int ret, cpu;
> > +
> > +    of_for_each_phandle(&it, ret, cspmu->dev->of_node, "cpus", NULL, 
> > 0) {
> > +        cpu = of_cpu_node_to_id(it.node);
> > +        if (cpu < 0)
> > +            continue;
> > +        cpumask_set_cpu(cpu, &cspmu->associated_cpus);
> > +    }
> > +    return ret;
> > +}
> > +
> > static int arm_cspmu_get_cpus(struct arm_cspmu *cspmu)
> > {
> > -    return arm_cspmu_acpi_get_cpus(cspmu);
> > +    int ret = 0;
> > +
> > +    if (has_acpi_companion(cspmu->dev))
> > +        ret = arm_cspmu_acpi_get_cpus(cspmu);
> > +    else if (of_property_present(cspmu->dev->of_node, "cpus"))
> > +        ret = arm_cspmu_of_get_cpus(cspmu);
> > +    else
> > +        cpumask_copy(&cspmu->associated_cpus, cpu_possible_mask);
> > +
> > +    if (!ret && cpumask_empty(&cspmu->associated_cpus)) {
> > +        dev_dbg(cspmu->dev, "No cpu associated with the PMU\n");
> > +        ret = -ENODEV;
> > +    }
> > +    return ret;
> > }
> >
> > static int arm_cspmu_register_pmu(struct arm_cspmu *cspmu)
> > @@ -1246,11 +1280,18 @@ static const struct platform_device_id 
> > arm_cspmu_id[] = {
> > };
> > MODULE_DEVICE_TABLE(platform, arm_cspmu_id);
> >
> > +static const struct of_device_id arm_cspmu_of_match[] = {
> > +    { .compatible = "arm,coresight-pmu" },
> > +    {}
> > +};
> > +MODULE_DEVICE_TABLE(of, arm_cspmu_of_match);
> > +
> > static struct platform_driver arm_cspmu_driver = {
> >     .driver = {
> > -            .name = DRVNAME,
> > -            .suppress_bind_attrs = true,
> > -        },
> > +        .name = DRVNAME,
> > +        .of_match_table = arm_cspmu_of_match,
> > +        .suppress_bind_attrs = true,
> > +    },
> >     .probe = arm_cspmu_device_probe,
> >     .remove = arm_cspmu_device_remove,
> >     .id_table = arm_cspmu_id,
> > --
> > 2.39.2.101.g768bb238c484.dirty