linux-kernel - Re: [PATCH v8 1/3] perf: cavium: Support memory controller PMU counters

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Date:   Wed, 26 Jul 2017 13:08:02 -0700
From:   Greg KH <gregkh@...uxfoundation.org>
To:     David Daney <ddaney.cavm@...il.com>
Cc:     Borislav Petkov <bp@...en8.de>,
        Mark Rutland <mark.rutland@....com>,
        Suzuki K Poulose <Suzuki.Poulose@....com>,
        linux-pci@...r.kernel.org, Will Deacon <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jan Glauber <jan.glauber@...iumnetworks.com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v8 1/3] perf: cavium: Support memory controller PMU
 counters

On Wed, Jul 26, 2017 at 01:02:38PM -0700, David Daney wrote:
> On 07/26/2017 10:33 AM, Greg KH wrote:
> > On Wed, Jul 26, 2017 at 06:30:49PM +0200, Borislav Petkov wrote:
> > > On Wed, Jul 26, 2017 at 09:19:49AM -0700, Greg KH wrote:
> > > > On Wed, Jul 26, 2017 at 05:55:48PM +0200, Borislav Petkov wrote:
> > > > > On Wed, Jul 26, 2017 at 05:45:15PM +0200, Jan Glauber wrote:
> > > > > > The PMU/EDAC devices are all PCI devices do I need the 'struct pci_dev *'.
> > > > > > I'm not aware of other ways to access these devices. Please enlighten
> > > > > > me if I'm missing something.
> > > > > 
> > > > > Me enlighten you on Cavium hardware?! You're funny.
> > > > > 
> > > > > So I don't know whether the PCI hotplug code can run more than one
> > > > > function upon PCI ID detection. Probably Greg will say, write a
> > > > > multiplexer wrapper. :-)
> > > > 
> > > > -ENOCONTEXT....
> > > > 
> > > > Anyway, pci questions are best asked on the linux-pci@...r list.  And
> > > > yes, all PCI devices end up with a 'struct pci_dev *' automatically.
> > > 
> > > Simple: so they have a PCI ID of a memory contoller and want to hotplug
> > > two drivers for it. And those two drivers should remain independent from
> > > each other.
> > 
> > Hahahahaha, no.  That's crazy, you were right in guessing what my answer
> > was going to be :)
> > 
> 
> 
> Just to be clear about the situation, the device is a memory controller.  It
> has two main behaviors we are interested in:
> 
> A) Error Detection And Correction (EDAC).  This should be connected to the
> kernel's EDAC subsystem.  An existing driver (drivers/edac/thunderx_edac.c)
> does exactly this.
> 
> B) Performance Counters for actions taken in the corresponding memory. This
> should be connected to the kernel's perf framework as an uncore-PMU (the
> subject of this patch set).
> 
> It is a single PCI device.  What should the driver architecture look like to
> connect it to two different kernel subsystems?

Modify the drivers/edac/thunderx_edac.c code to add support for
performance counters.