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From:   "Shradha Todi" <shradha.t@samsung.com>
To:     "'Manivannan Sadhasivam'" <manivannan.sadhasivam@linaro.org>
Cc:     <lpieralisi@kernel.org>, <kw@linux.com>, <robh@kernel.org>,
        <bhelgaas@google.com>, <jingoohan1@gmail.com>,
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        <lukas.bulwahn@gmail.com>, <hongxing.zhu@nxp.com>,
        <pankaj.dubey@samsung.com>, <linux-kernel@vger.kernel.org>,
        <linux-pci@vger.kernel.org>
In-Reply-To: <20231130165514.GW3043@thinkpad>
Subject: RE: [PATCH v2 0/3] Add support for RAS DES feature in PCIe DW
 controller
Date:   Mon, 4 Dec 2023 14:10:06 +0530
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> -----Original Message-----
> From: Manivannan Sadhasivam =5Bmailto:manivannan.sadhasivam=40linaro.org=
=5D
> Sent: 30 November 2023 22:25
> To: Shradha Todi <shradha.t=40samsung.com>
> Cc: lpieralisi=40kernel.org; kw=40linux.com; robh=40kernel.org;
> bhelgaas=40google.com; jingoohan1=40gmail.com;
> gustavo.pimentel=40synopsys.com; josh=40joshtriplett.org;
> lukas.bulwahn=40gmail.com; hongxing.zhu=40nxp.com;
> pankaj.dubey=40samsung.com; linux-kernel=40vger.kernel.org; linux-
> pci=40vger.kernel.org
> Subject: Re: =5BPATCH v2 0/3=5D Add support for RAS DES feature in PCIe D=
W
> controller
>=20
> On Thu, Nov 30, 2023 at 05:20:41PM +0530, Shradha Todi wrote:
> > DesignWare controller provides a vendor specific extended capability
> > called RASDES as an IP feature. This extended capability  provides
> > hardware information like:
> >  - Debug registers to know the state of the link or controller.
> >  - Error injection mechanisms to inject various PCIe errors including
> >    sequence number, CRC
> >  - Statistical counters to know how many times a particular event
> >    occurred
> >
> > However, in Linux we do not have any generic or custom support to be
> > able to use this feature in an efficient manner. This is the reason we
> > are proposing this framework. Debug and bring up time of high-speed
> > IPs are highly dependent on costlier hardware analyzers and this
> > solution will in some ways help to reduce the HW analyzer usage.
> >
> > The debugfs entries can be used to get information about underlying
> > hardware and can be shared with user space. Separate debugfs entries
> > has been created to cater to all the DES hooks provided by the controll=
er.
> > The debugfs entries interacts with the RASDES registers in the
> > required sequence and provides the meaningful data to the user. This
> > eases the effort to understand and use the register information for
> debugging.
> >
> > v1 version was posted long back and for some reasons I couldn't work
> > on it. I apologize for the long break. I'm restarting this activity
> > and have taken care of all previous review comments shared.
> > v1:
> > https://lore.kernel.org/all/20210518174618.42089-1-shradha.t=40samsung.=
c
> > om/T/
> >
>=20
> There is already a series floating to add similar functionality via perf
> subsystem: https://lore.kernel.org/linux-pci/20231121013400.18367-1-
> xueshuai=40linux.alibaba.com/
>=20
> - Mani
>=20

Hi Mani,

The series proposed in perf includes only time based-analysis and event cou=
nters which will monitor performance (Group 6 and 7). The patch or framewor=
k that we have proposed includes debug information, error injection facilit=
y and error counters (Group 0 - 5) which are not included as part of the fu=
nctionality implemented via perf. In my opinion, these functionalities don'=
t count as performance monitoring or counters but rather as debug counters.=
 How about we take this up as a debugfs framework as proposed in my patch?=
=20
Or if others feel it can be taken via perf driver then I am happy to extend=
 the perf driver if authors do not have objection. Let me know what you thi=
nk of this? Meanwhile I will review the perf patches and share my feedback.

> > Shradha Todi (3):
> >   PCI: dwc: Add support for vendor specific capability search
> >   PCI: debugfs: Add support for RASDES framework in DWC
> >   PCI: dwc: Create debugfs files in DWC driver
> >
> >  drivers/pci/controller/dwc/Kconfig            =7C   8 +
> >  drivers/pci/controller/dwc/Makefile           =7C   1 +
> >  .../controller/dwc/pcie-designware-debugfs.c  =7C 476
> ++++++++++++++++++
> >  .../controller/dwc/pcie-designware-debugfs.h  =7C   0
> >  drivers/pci/controller/dwc/pcie-designware.c  =7C  20 +
> > drivers/pci/controller/dwc/pcie-designware.h  =7C  18 +
> >  6 files changed, 523 insertions(+)
> >  create mode 100644
> > drivers/pci/controller/dwc/pcie-designware-debugfs.c
> >  create mode 100644
> > drivers/pci/controller/dwc/pcie-designware-debugfs.h
> >
> > --
> > 2.17.1
> >
>=20
> --
> =E0=AE=AE=E0=AE=A3=E0=AE=BF=E0=AE=B5=E0=AE=A3=E0=AF=8D=E0=AE=A3=E0=AE=A9=
=E0=AF=8D=20=E0=AE=9A=E0=AE=A4=E0=AE=BE=E0=AE=9A=E0=AE=BF=E0=AE=B5=E0=AE=AE=
=E0=AF=8D=0D=0A=0D=0A