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

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Message-ID: <0a0daa94-bad7-cbb5-e421-f8e9d6c79d54@arm.com>
Date:   Wed, 26 Jul 2017 16:17:11 +0100
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Jan Glauber <jan.glauber@...iumnetworks.com>,
        Borislav Petkov <bp@...en8.de>
Cc:     Mark Rutland <mark.rutland@....com>,
        Will Deacon <will.deacon@....com>,
        linux-arm-kernel@...ts.infradead.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v8 1/3] perf: cavium: Support memory controller PMU
 counters

On 26/07/17 16:13, Jan Glauber wrote:
> On Wed, Jul 26, 2017 at 04:55:22PM +0200, Borislav Petkov wrote:
>> On Wed, Jul 26, 2017 at 03:35:25PM +0100, Suzuki K Poulose wrote:
>>> So the Cavium EDACs, which appear as PCI devices have a PMU attached to it.
>>
>> Cavium EDACs?
>>
>> So let me set something straight first: An EDAC driver simply talks to
>> some RAS IP block and reports errors. It shouldn't have anything to do
>> with a PMU.
>>
>>> In order to build this PMU driver as a module, we need a way to load the module
>>> automatically based on the PCI id. However, since the EDAC driver already
>>> registers with that PCI id, we cannot use the same for the PMU. Ideally,
>>
>> So this is strange. There's a single PCI ID but multiple functionalities
>> behind it?
>
> Yes, but I would still not call a memory controller a RAS IP block.

> There are a number of registers on the memory controller (or on the OCX
> TLK interconnect), and while some of them are RAS related there are also
> other registers in the same device like the counters we want to access
> via PMU code.

How about adding a soc specific (wrapper) driver for the memory controller, which
could use the PCI id and trigger EDAC and PMU drivers (based on what is
selected by configs)  ?

Suzuki