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SubjectRe: [PATCH v5 3/8] hisi_ptt: Register PMU device for PTT trace
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On 2022/3/8 20:06, Jonathan Cameron wrote:
> On Tue, 8 Mar 2022 19:13:08 +0800
> Yicong Yang <yangyicong@huawei.com> wrote:
>
>> On 2022/3/8 18:21, Jonathan Cameron wrote:
>>> On Tue, 8 Mar 2022 16:49:25 +0800
>>> Yicong Yang <yangyicong@hisilicon.com> wrote:
>>>
>>>> Register PMU device of PTT trace, then users can use trace through perf
>>>> command. The driver makes use of perf AUX trace and support following
>>>> events to configure the trace:
>>>>
>>>> - filter: select Root port or Endpoint to trace
>>>> - type: select the type of traced TLP headers
>>>> - direction: select the direction of traced TLP headers
>>>> - format: select the data format of the traced TLP headers
>>>>
>>>> This patch adds the PMU driver part of PTT trace. The perf command support
>>>> of PTT trace is added in the following patch.
>>>>
>>>> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
>>>
>>> It seems to me that you ended up doing both suggestions for
>>> how to clean up the remove order when it was meant to be
>>> a question of picking one or the other.
>>>
>>> Otherwise this looks good to me - so with that tidied up
>>>
>>
>> Hi Jonathan,
>>
>> Thanks for the comments. I'd like to illustrate the reason why I decide to
>> manually unregister the PMU device.
>>
>> The DMA buffers are devm allocated when necessary. They're only allocated
>> when user is going to use the PTT in the first time after the driver's probe,
>> so when driver removal the buffers are released prior to the PMU device's
>> unregistration. I think there's a race condition.
>>
>> IIUC, The PMU device(as the user interface) should be unregistered first then
>> we're safe to free the DMA buffers. But unregister the PMU device by devm
>> cannot keep that order.
>
> Ok. Please add a comment in the remove() giving this reasoning.
>

Sure will add a comment for the reason why we need this manual unregistration in remove().

> Jonathan
>
>>
>> Thanks,
>> Yicong
>>
>>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
>>>
>>>> ---
>>>
>>>> +
>>>> +static int hisi_ptt_register_pmu(struct hisi_ptt *hisi_ptt)
>>>> +{
>>>> + u16 core_id, sicl_id;
>>>> + char *pmu_name;
>>>> + u32 reg;
>>>> +
>>>> + hisi_ptt->hisi_ptt_pmu = (struct pmu) {
>>>> + .module = THIS_MODULE,
>>>> + .capabilities = PERF_PMU_CAP_EXCLUSIVE | PERF_PMU_CAP_ITRACE,
>>>> + .task_ctx_nr = perf_sw_context,
>>>> + .attr_groups = hisi_ptt_pmu_groups,
>>>> + .event_init = hisi_ptt_pmu_event_init,
>>>> + .setup_aux = hisi_ptt_pmu_setup_aux,
>>>> + .free_aux = hisi_ptt_pmu_free_aux,
>>>> + .start = hisi_ptt_pmu_start,
>>>> + .stop = hisi_ptt_pmu_stop,
>>>> + .add = hisi_ptt_pmu_add,
>>>> + .del = hisi_ptt_pmu_del,
>>>> + };
>>>> +
>>>> + reg = readl(hisi_ptt->iobase + HISI_PTT_LOCATION);
>>>> + core_id = FIELD_GET(HISI_PTT_CORE_ID, reg);
>>>> + sicl_id = FIELD_GET(HISI_PTT_SICL_ID, reg);
>>>> +
>>>> + pmu_name = devm_kasprintf(&hisi_ptt->pdev->dev, GFP_KERNEL, "hisi_ptt%u_%u",
>>>> + sicl_id, core_id);
>>>> + if (!pmu_name)
>>>> + return -ENOMEM;
>>>> +
>>>> + return perf_pmu_register(&hisi_ptt->hisi_ptt_pmu, pmu_name, -1);
>>>
>>> As below, you can put back the devm cleanup that you had in v4 now you
>>> have modified how the filter cleanup is done to also be devm managed.
>>>
>>>> +}
>>>> +
>>>> /*
>>>> * The DMA of PTT trace can only use direct mapping, due to some
>>>> * hardware restriction. Check whether there is an IOMMU or the
>>>> @@ -303,15 +825,32 @@ static int hisi_ptt_probe(struct pci_dev *pdev,
>>>>
>>>> pci_set_master(pdev);
>>>>
>>>> + ret = hisi_ptt_register_irq(hisi_ptt);
>>>> + if (ret)
>>>> + return ret;
>>>> +
>>>> ret = hisi_ptt_init_ctrls(hisi_ptt);
>>>> if (ret) {
>>>> pci_err(pdev, "failed to init controls, ret = %d.\n", ret);
>>>> return ret;
>>>> }
>>>>
>>>> + ret = hisi_ptt_register_pmu(hisi_ptt);
>>>> + if (ret) {
>>>> + pci_err(pdev, "failed to register pmu device, ret = %d", ret);
>>>> + return ret;
>>>> + }
>>>> +
>>>> return 0;
>>>> }
>>>>
>>>> +void hisi_ptt_remove(struct pci_dev *pdev)
>>>> +{
>>>> + struct hisi_ptt *hisi_ptt = pci_get_drvdata(pdev);
>>>> +
>>>> + perf_pmu_unregister(&hisi_ptt->hisi_ptt_pmu);
>>>
>>> Now you have the filter cleanup occurring using a devm_add_action_or_reset()
>>> there is no need to have a manual cleanup of this - you can
>>> use the approach of a devm_add_action_or_reset like you had in v4.
>>>
>>> As it is the last call in the probe() order it will be the first one
>>> called in the device managed cleanup.
>>>
>>>> +}
>>>> +
>>>
>>>
>>> .
>>>
>
> .
>

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