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

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On 07/26/2017 07:29 PM, Greg KH wrote:
On Wed, Jul 26, 2017 at 02:02:42PM -0700, David Daney wrote:
On 07/26/2017 01:08 PM, Greg KH wrote:
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@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?

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


Thanks Greg.  This adds some clarity to the situation.

This technique does slightly complicate the mapping of files and directories
in the kernel source tree to maintainers.

Also, if a given configuration disables CONFIG_EDAC there is some hackery
needed to get the perf portion of the driver included.

Well, you all deserve it for trying to have a single PCI device do
multiple things at the same time.  There's no real good reason for
creating hardware that way, PCI devices are "free", you should go throw
a printed copy of the PCI spec at the firmware developers who did this
to you.

The problem lies in something even more congealed than the "firmware". The PCI topology is etched in to the very fabric of the silicon of the SoC.



Then get them to fix the firmware so you have multiple PCI devices...

good luck!

We'll use all of that we can get!  Thanks.



greg k-h





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