linux-kernel - Re: [PATCH RFC] perf:Add driver for HiSilicon PCIe PMU

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Date:   Thu, 19 Mar 2020 09:34:45 +0800
From:   Qi Liu <liuqi115@...wei.com>
To:     Mark Rutland <mark.rutland@....com>,
        Robin Murphy <robin.murphy@....com>
CC:     <will@...nel.org>, <bhelgaas@...gle.com>,
        <linux-pci@...r.kernel.org>, <linuxarm@...wei.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC] perf:Add driver for HiSilicon PCIe PMU

Thanks for reviewing this patch, will fix these in v2 patch!

On 2020/3/13 21:59, Mark Rutland wrote:
> On Fri, Mar 13, 2020 at 01:23:53PM +0000, Robin Murphy wrote:
>> On 2020-03-12 12:06 pm, Qi Liu wrote:
>>> From: Qi liu <liuqi115@...wei.com>
> 
> [...]
> 
>>> +#define HISI_PCIE_EVENT_SHIFT_M			GENMASK(15, 0)
>>> +#define HISI_PCIE_SUBEVENT_SHIFT_M		GENMASK(31, 16)
>>> +#define HISI_PCIE_SUBEVENT_SHIFT_S		16
>>> +#define HISI_PCIE_PORT_SHIFT_M			GENMASK(7, 0)
>>> +#define HISI_PCIE_FUNC_SHIFT_M			GENMASK(15, 8)
>>> +#define HISI_PCIE_FUNC_SHIFT_S			8
>>
>> So "SHIFT_S" means "shift" and "SHIFT_M" actually means "mask"? That's
>> unnecessarily confusing. Furthermore it might be helpful if there was a more
>> obvious distinction between hardware register fields and config fields.
> 
> Also, If you use the FIELD_GET() and FIELD_PREP() helpers, you only need
> to define the mask. See <linux/bitfield.h>.
> 
>>> +int hisi_pcie_pmu_event_init(struct perf_event *event)
>>> +{
>>> +	struct hisi_pcie_pmu *pcie_pmu = to_pcie_pmu(event->pmu);
>>> +	struct hw_perf_event *hwc = &event->hw;
>>> +	u32 subevent_id, event_id, func_id, port_id;
>>> +
>>> +	if (event->attr.type != event->pmu->type)
>>> +		return -ENOENT;
>>> +
>>> +	/*
>>> +	 * We do not support sampling as the counters are all shared by all
>>> +	 * CPU cores in a CPU die(SCCL). Also we do not support attach to a
>>
>> Do the PCIe counters have anything to do with CPU clusters at all?
>>
>>> +	 * task(per-process mode)
>>> +	 */
>>> +	if (is_sampling_event(event) || event->attach_state & PERF_ATTACH_TASK)
>>> +		return -EOPNOTSUPP;
>>> +
>>> +	/*
>>> +	 * The uncore counters not specific to any CPU, so cannot
>>> +	 * support per-task
>>> +	 */
>>> +	if (event->cpu < 0)
>>> +		return -EINVAL;
>>> +
>>> +	/*
>>> +	 * Validate if the events in group does not exceed the
>>> +	 * available counters in hardware.
>>> +	 */
>>> +	if (!hisi_validate_event_group(event))
>>> +		return -EINVAL;
>>> +
>>> +	event_id = event->attr.config && HISI_PCIE_EVENT_SHIFT_M;
>>
>> Really? Are you sure you've tested this properly?
> 
> If you had:
> 
> #define HISI_PCI_EVENT_ID	GENMASK(15, 0)
> #define HISI_PCI_SUBEVENT_ID	GENMASK(31, 16)
> 
> ... here you could do:
> 
> 	event_id = FIELD_GET(HISI_PCI_EVENT_ID, event->attr.config);
> 
>>
>>> +	subevent_id = (event->attr.config && HISI_PCIE_SUBEVENT_SHIFT_M)
>>> +		       >> HISI_PCIE_SUBEVENT_SHIFT_S;
> 
> ... and:
> 
> 	subevent_id = FIELD_GET(HISI_PCI_SUBEVENT_ID, event->attr.config);
> 
> ... and so on for other fields.
> 
> Thanks,
> Mark.
> 
> .
>