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Date: Tue, 8 Mar 2022 12:06:07 +0000
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Yicong Yang <yangyicong@...wei.com>
CC: Yicong Yang <yangyicong@...ilicon.com>,
<gregkh@...uxfoundation.org>, <helgaas@...nel.org>,
<alexander.shishkin@...ux.intel.com>, <lorenzo.pieralisi@....com>,
<will@...nel.org>, <mark.rutland@....com>,
<mathieu.poirier@...aro.org>, <suzuki.poulose@....com>,
<mike.leach@...aro.org>, <leo.yan@...aro.org>,
<daniel.thompson@...aro.org>, <joro@...tes.org>,
<john.garry@...wei.com>, <shameerali.kolothum.thodi@...wei.com>,
<robin.murphy@....com>, <peterz@...radead.org>, <mingo@...hat.com>,
<acme@...nel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<coresight@...ts.linaro.org>, <linux-pci@...r.kernel.org>,
<linux-perf-users@...r.kernel.org>,
<iommu@...ts.linux-foundation.org>, <prime.zeng@...wei.com>,
<liuqi115@...wei.com>, <zhangshaokun@...ilicon.com>,
<linuxarm@...wei.com>, <song.bao.hua@...ilicon.com>
Subject: Re: [PATCH v5 3/8] hisi_ptt: Register PMU device for PTT trace
On Tue, 8 Mar 2022 19:13:08 +0800
Yicong Yang <yangyicong@...wei.com> wrote:
> On 2022/3/8 18:21, Jonathan Cameron wrote:
> > On Tue, 8 Mar 2022 16:49:25 +0800
> > Yicong Yang <yangyicong@...ilicon.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@...ilicon.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.
Jonathan
>
> Thanks,
> Yicong
>
> > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.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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