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

[David Daney]

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@vger 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?

Thanks,
David Daney