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

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Message-ID: <1a2eedea-040d-c746-eaf0-1d8085b3f2bf@gmail.com>
Date:   Wed, 26 Jul 2017 13:02:38 -0700
From:   David Daney <ddaney.cavm@...il.com>
To:     Greg KH <gregkh@...uxfoundation.org>,
        Borislav Petkov <bp@...en8.de>
Cc:     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 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?

Thanks,
David Daney