Re: [PATCH v5 3/4] drivers/perf: add DesignWare PCIe PMU driver

[Baolin Wang]

On 5/22/2023 11:54 AM, Shuai Xue wrote:
> This commit adds the PCIe Performance Monitoring Unit (PMU) driver support
> for T-Head Yitian SoC chip. Yitian is based on the Synopsys PCI Express
> Core controller IP which provides statistics feature. The PMU is not a PCIe
> Root Complex integrated End Point(RCiEP) device but only register counters
> provided by each PCIe Root Port.
>
> To facilitate collection of statistics the controller provides the
> following two features for each Root Port:
>
> - Time Based Analysis (RX/TX data throughput and time spent in each
>    low-power LTSSM state)
> - Event counters (Error and Non-Error for lanes)
>
> Note, only one counter for each type and does not overflow interrupt.
>
> This driver adds PMU devices for each PCIe Root Port. And the PMU device is
> named based the BDF of Root Port. For example,
>
>      30:03.0 PCI bridge: Device 1ded:8000 (rev 01)
>
> the PMU device name for this Root Port is dwc_rootport_3018.
>
> Example usage of counting PCIe RX TLP data payload (Units of 16 bytes)::
>
>      $# perf stat -a -e dwc_rootport_3018/Rx_PCIe_TLP_Data_Payload/
>
> average RX bandwidth can be calculated like this:
>
>      PCIe TX Bandwidth = PCIE_TX_DATA * 16B / Measure_Time_Window
>
> Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Link: https://lore.kernel.org/oe-kbuild-all/202305170639.XU3djFZX-lkp@xxxxxxxxx/
> ---

[snip]

> +static int dwc_pcie_pmu_remove(struct platform_device *pdev)
> +{
> +	struct dwc_pcie_pmu_priv *priv = platform_get_drvdata(pdev);
> +	struct dwc_pcie_pmu *pcie_pmu;
> +
> +	list_for_each_entry(pcie_pmu, &priv->pmu_nodes, pmu_node) {
> +		cpuhp_state_remove_instance(dwc_pcie_pmu_hp_state,
> +					    &pcie_pmu->cpuhp_node);
> +		perf_pmu_unregister(&pcie_pmu->pmu);
> +	}
> +
> +	return 0;
> +}
> +
> +static int dwc_pcie_pmu_probe(struct platform_device *pdev)
> +{
> +	struct dwc_pcie_pmu_priv *priv;
> +
> +	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> +	if (!priv)
> +		return -ENOMEM;
> +
> +	priv->dev = &pdev->dev;
> +	platform_set_drvdata(pdev, priv);
> +
> +	/* If one PMU registration fails, remove all. */
> +	if (__dwc_pcie_pmu_probe(priv))
> +		dwc_pcie_pmu_remove(pdev);

In this case, you should return error from __dwc_pcie_pmu_probe() 
instead of returning 0, to release the requested resources of the PMU 
deivce.

> +
> +	return 0;
> +}
> +
> +static void dwc_pcie_pmu_migrate(struct dwc_pcie_pmu *pcie_pmu, unsigned int cpu)
> +{
> +	/* This PMU does NOT support interrupt, just migrate context. */
> +	perf_pmu_migrate_context(&pcie_pmu->pmu, pcie_pmu->oncpu, cpu);
> +	pcie_pmu->oncpu = cpu;
> +}
> +
> +static int dwc_pcie_pmu_online_cpu(unsigned int cpu, struct hlist_node *cpuhp_node)
> +{
> +	struct dwc_pcie_pmu *pcie_pmu;
> +	struct pci_dev *pdev;
> +	int node;
> +
> +	pcie_pmu = hlist_entry_safe(cpuhp_node, struct dwc_pcie_pmu, cpuhp_node);
> +	pdev = pcie_pmu->pdev;
> +	node = dev_to_node(&pdev->dev);
> +
> +	if (node != NUMA_NO_NODE && cpu_to_node(pcie_pmu->oncpu) != node &&
> +	    cpu_to_node(cpu) == node)
> +		dwc_pcie_pmu_migrate(pcie_pmu, cpu);
> +
> +	return 0;
> +}
> +
> +static int dwc_pcie_pmu_offline_cpu(unsigned int cpu, struct hlist_node *cpuhp_node)
> +{
> +	struct dwc_pcie_pmu *pcie_pmu;
> +	struct pci_dev *pdev;
> +	int node;
> +	cpumask_t mask;
> +	unsigned int target;
> +
> +	pcie_pmu = hlist_entry_safe(cpuhp_node, struct dwc_pcie_pmu, cpuhp_node);
> +	if (cpu != pcie_pmu->oncpu)
> +		return 0;
> +
> +	pdev = pcie_pmu->pdev;
> +	node = dev_to_node(&pdev->dev);
> +	if (cpumask_and(&mask, cpumask_of_node(node), cpu_online_mask) &&
> +	    cpumask_andnot(&mask, &mask, cpumask_of(cpu)))
> +		target = cpumask_any(&mask);
> +	else
> +		target = cpumask_any_but(cpu_online_mask, cpu);
> +	if (target < nr_cpu_ids)
> +		dwc_pcie_pmu_migrate(pcie_pmu, target);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver dwc_pcie_pmu_driver = {
> +	.probe = dwc_pcie_pmu_probe,
> +	.remove = dwc_pcie_pmu_remove,
> +	.driver = {.name = "dwc_pcie_pmu",},
> +};
> +
> +static int __init dwc_pcie_pmu_init(void)
> +{
> +	int ret;
> +
> +	ret = cpuhp_setup_state_multi(CPUHP_AP_ONLINE_DYN,
> +				      "perf/dwc_pcie_pmu:online",
> +				      dwc_pcie_pmu_online_cpu,
> +				      dwc_pcie_pmu_offline_cpu);
> +	if (ret < 0)
> +		return ret;
> +
> +	dwc_pcie_pmu_hp_state = ret;
> +
> +	ret = platform_driver_register(&dwc_pcie_pmu_driver);
> +	if (ret) {
> +		cpuhp_remove_multi_state(dwc_pcie_pmu_hp_state);
> +		return ret;
> +	}
> +
> +	dwc_pcie_pmu_dev = platform_device_register_simple(
> +				"dwc_pcie_pmu", PLATFORM_DEVID_NONE, NULL, 0);
> +	if (IS_ERR(dwc_pcie_pmu_dev)) {
> +		platform_driver_unregister(&dwc_pcie_pmu_driver);
> +		return PTR_ERR(dwc_pcie_pmu_dev);
> +	}
> +
> +	return 0;
> +}
> +
> +static void __exit dwc_pcie_pmu_exit(void)
> +{
> +	platform_device_unregister(dwc_pcie_pmu_dev);
> +	platform_driver_unregister(&dwc_pcie_pmu_driver);

You should also call 'cpuhp_remove_multi_state()' when exiting the driver.

With above issues fixed, you can add:
Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>