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

[Ilkka Koskinen <ilkka@os.amperecomputing.com>]

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@arm.com>
> ---
> 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.

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

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
>
>