Re: [PATCH v10 4/5] drivers/perf: add DesignWare PCIe PMU driver

[Ilkka Koskinen]

On Wed, 15 Nov 2023, Shuai Xue wrote:
> On 2023/11/15 08:07, Ilkka Koskinen wrote:
> > Hi Shuai,
> >
> > On Sat, 4 Nov 2023, 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 a PCIe
> > > configuration space register block provided by each PCIe Root Port in a
> > > Vendor-Specific Extended Capability named RAS D.E.S (Debug, Error
> > > injection, and Statistics).
> > >
> > > To facilitate collection of statistics the controller provides the
> > > following two features for each Root Port:
> > >
> > > - one 64-bit counter for Time Based Analysis (RX/TX data throughput and
> > >  time spent in each low-power LTSSM state) and
> > > - one 32-bit counter for Event Counting (error and non-error events for
> > >  a specified lane)
> > >
> > > Note: There is no interrupt for counter overflow.
> > >
> > > 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 bytes)::
> > >
> > >    $# perf stat -a -e dwc_rootport_3018/Rx_PCIe_TLP_Data_Payload/
> > >
> > > average RX bandwidth can be calculated like this:
> > >
> > >    PCIe TX Bandwidth = Rx_PCIe_TLP_Data_Payload / Measure_Time_Window
> > >
> > > Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
> > > Reviewed-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx>
> > > Reviewed-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
> > > Reviewed-by: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
> >
> > Thanks for the driver! I finally found some time to test your driver on AmpereOne and it seemed to work fine.
>
> Glad to hear that. Could you please explicitly give me you tested-by tag? I could add it in next version.

Sure, I'll reply to the cover letter mail.

> > I had to do a couple of changes though such as adding Ampere vendor ID
and support multiple PCIe domains. Given your driver is already in v10 and you have got quite a few reviewed and acked bys, I wonder if it's better to add my changes to your patches or me to create new patches on top of yours? I'm fine with either. Any thoughts?
> I prefer new separate patches, so that we can review them in a new loop.

Sounds good to me.

Cheers, Ilkka

> > Cheers, Ilkka
>
> Best Regard,
> Shuai