Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for Cavium ThunderX

From	Jan Glauber <jan.glauber@caviumnetworks.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for Cavium ThunderX
Date	2016-02-15 16:40 +0100
Message-ID	<r2tpM-2SR-15@gated-at.bofh.it> (permalink)
References	<r1pex-17H-9@gated-at.bofh.it> <r1pex-17H-7@gated-at.bofh.it> <r1pRh-1EI-23@gated-at.bofh.it> <r2sk2-2aV-9@gated-at.bofh.it> <r2sk2-2aV-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Feb 15, 2016 at 02:27:27PM +0000, Mark Rutland wrote:
> > > > 1) The PMU detection solely relies on PCI device detection. If a
> > > >    matching PCI device is found the PMU is created. The code can deal
> > > >    with multiple units of the same type, e.g. more than one memory
> > > >    controller.
> > > 
> > > I see below that the driver has an initcall that runs regardless of
> > > whether the PCI device exists, and looks at the MIDR. That's clearly not
> > > string PCI device detection.
> > > 
> > > Why is this not a true PCI driver that only gets probed if the PCI
> > > device exists? 
> > 
> > It is not a PCI driver because there are already drivers like edac that
> > will access these PCI devices. The uncore driver only accesses the
> > performance counters, which are not used by the other drivers.
> 
> Several drivers are accessing the same device?
> 
> That sounds somewhat scary.

I've double checked that the edac drivers do not access the performance
counters at all. It felt cleaner to me to keep the performance counter code
seperated from edac.

Jan

Thread

[RFC PATCH 1/7] arm64/perf: Basic uncore counter support for Cavium ThunderX Jan Glauber <jglauber@cavium.com> - 2016-02-12 18:00 +0100
  Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Mark Rutland <mark.rutland@arm.com> - 2016-02-12 18:40 +0100
    Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX David Daney <ddaney.cavm@gmail.com> - 2016-02-13 02:50 +0100
      Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Mark Rutland <mark.rutland@arm.com> - 2016-02-15 12:40 +0100
    Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Mark Rutland <mark.rutland@arm.com> - 2016-02-15 15:30 +0100
      Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Mark Rutland <mark.rutland@arm.com> - 2016-02-15 15:50 +0100
      Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Jan Glauber <jan.glauber@caviumnetworks.com> - 2016-02-15 16:40 +0100
    Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Jan Glauber <jan.glauber@caviumnetworks.com> - 2016-02-15 15:50 +0100
    Re: [RFC PATCH 1/7] arm64/perf: Basic uncore counter support for  Cavium ThunderX Jan Glauber <jan.glauber@caviumnetworks.com> - 2016-02-16 09:50 +0100

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