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Date: Wed, 16 Jun 2021 09:54:23 +0800
From: "liuqi (BA)" <liuqi115@...wei.com>
To: Will Deacon <will@...nel.org>, Linuxarm <linuxarm@...wei.com>
CC: <mark.rutland@....com>, <bhelgaas@...gle.com>,
<linux-pci@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <zhangshaokun@...ilicon.com>
Subject: Re: [PATCH v6 2/2] drivers/perf: hisi: Add driver for HiSilicon PCIe
PMU
Hi Will,
On 2021/6/15 17:35, Will Deacon wrote:
> On Tue, Jun 15, 2021 at 04:57:09PM +0800, liuqi (BA) wrote:
>> On 2021/6/12 0:23, Will Deacon wrote:
>>> On Mon, May 31, 2021 at 09:32:31PM +0800, Qi Liu wrote:
>>>> PCIe PMU Root Complex Integrated End Point(RCiEP) device is supported
>>>> to sample bandwidth, latency, buffer occupation etc.
>>>>
>>>> Each PMU RCiEP device monitors multiple Root Ports, and each RCiEP is
>>>> registered as a PMU in /sys/bus/event_source/devices, so users can
>>>> select target PMU, and use filter to do further sets.
>>>>
>>>> Filtering options contains:
>>>> event - select the event.
>>>> subevent - select the subevent.
>>>> port - select target Root Ports. Information of Root Ports
>>>> are shown under sysfs.
>>>> bdf - select requester_id of target EP device.
>>>> trig_len - set trigger condition for starting event statistics.
>>>> trigger_mode - set trigger mode. 0 means starting to statistic when
>>>> bigger than trigger condition, and 1 means smaller.
>>>> thr_len - set threshold for statistics.
>>>> thr_mode - set threshold mode. 0 means count when bigger than
>>>> threshold, and 1 means smaller.
>>>>
>>>> Reviewed-by: John Garry <john.garry@...wei.com>
>>>> Signed-off-by: Qi Liu <liuqi115@...wei.com>
>>>> ---
>>>> MAINTAINERS | 6 +
>>>> drivers/perf/Kconfig | 2 +
>>>> drivers/perf/Makefile | 1 +
>>>> drivers/perf/pci/Kconfig | 16 +
>>>> drivers/perf/pci/Makefile | 2 +
>>>> drivers/perf/pci/hisilicon/Makefile | 3 +
>>>> drivers/perf/pci/hisilicon/hisi_pcie_pmu.c | 1019 ++++++++++++++++++++++++++++
>>>
>>> Can we keep this under drivers/perf/hisilicon/ please? I don't see the
>>> need to create a 'pci' directory here.
>>>
>> So how about drivers/perf/hisilicon/pci? as hisi_pcie_pmu.c do not use
>> hisi_uncore_pmu framework.
>
> That's up to you. As long as it's _somewhere_ under drivers/perf/hisilicon/,
> then I'm not too fussed.
>
ok, got it, will move the driver to perf/hisilicon in next version.
>>>> +static void hisi_pcie_parse_reg_value(struct hisi_pcie_pmu *pcie_pmu,
>>>> + u32 reg_off, u16 *arg0, u16 *arg1)
>>>> +{
>>>> + u32 val = readl(pcie_pmu->base + reg_off);
>>>> +
>>>> + *arg0 = val & 0xffff;
>>>> + *arg1 = (val & 0xffff0000) >> 16;
>>>> +}
>>>
>>> Define a new type for the pair of values and return that directly?
>>>
>> Sorry, I'm not sure about how to fix this, do you mean add a union like
>> this?
>> union reg_val {
>> struct {
>> u16 arg0;
>> u16 arg1;
>> }
>> u32 val;
>> }
>
> I was just thinking along the lines of:
>
> struct hisi_pcie_reg_pair {
> u16 lo;
> u16 hi;
> };
>
> static struct hisi_pcie_reg_pair
> hisi_pcie_parse_reg_value(struct hisi_pcie_pmu *pcie_pmum u32 reg_off)
> {
> u32 val = readl_relaxed(pcie_pmu->base + reg_off);
> struct hisi_pcie_reg_pair regs = {
> .lo = val,
> .hi = val >> 16,
> };
>
> return regs;
> }
>
> Does that work?
>
yes, will fix this, thanks.
>>>> +/*
>>>> + * The bandwidth, latency, bus utilization and buffer occupancy features are
>>>> + * calculated from data in HISI_PCIE_CNT and extended data in HISI_PCIE_EXT_CNT.
>>>> + * Other features are obtained only by HISI_PCIE_CNT.
>>>> + * So data and data_ext are processed in this function to get performanace
>>>> + * value like, bandwidth, latency, etc.
>>>> + */
>>>> +static u64 hisi_pcie_pmu_get_performance(struct perf_event *event, u64 data,
>>>> + u64 data_ext)
>>>> +{
>>>> +#define CONVERT_DW_TO_BYTE(x) (sizeof(u32) * (x))
>>>
>>> I don't know what a "DW" is, but this macro adds nothing...
>>
>> DW means double words, and 1DW = 4Bytes, value in hardware counter means DW
>> so I wanna change it into Byte.
>> So how about using 4*data here and adding code comment to explain it.
>
> Just remove the macro and replace it's single user with sizeof(u32) * x
>
ok, thanks.
>>>> + /* Process data to set unit of latency as "us". */
>>>> + if (is_latency_event(idx))
>>>> + return div64_u64(data * us_per_cycle, data_ext);
>>>> +
>>>> + if (is_bus_util_event(idx))
>>>> + return div64_u64(data * us_per_cycle, data_ext);
>>>> +
>>>> + if (is_buf_util_event(idx))
>>>> + return div64_u64(data, data_ext * us_per_cycle);
>>>
>>> Why do we need to do all this division in the kernel? Can't we just expose
>>> the underlying values and let userspace figure out what it wants to do with
>>> the numbers?
>>>
>> Our PMU hardware support 8 sets of counters to count bandwidth, latency and
>> utilization events.
>>
>> For example, when users set latency event, common counter will count delay
>> cycles, and extern counter count number of PCIe packets automaticly. And we
>> do not have a event number for counting number of PCIe packets.
>>
>> So this division cannot move to userspace tool.
>
> Why can't you expose the packet counter as an extra event to userspace?
>
Maybe I didn’t express it clearly.
As there is no hardware event number for PCIe packets counting, extern
counter count packets *automaticly* when latency events is selected by
users.
This means users cannot set "config=0xXX" to start packets counting
event. So we can only get the value of counter and extern counter in
driver and do the division, then pass the result to userspace.
> Will
> .
>
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