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

[Shuai Xue <xueshuai@linux.alibaba.com>]

On 2023/5/29 14:13, Baolin Wang wrote:
> 
> 
> 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@linux.alibaba.com>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Link: https://lore.kernel.org/oe-kbuild-all/202305170639.XU3djFZX-lkp@intel.com/
>> ---
> 
> [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.

You are right, will fix it in next version.

> 
>> +
>> +    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.

Good catch, will add it in next version.


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

Thank you :)

Best Regards,
Shuai