linux-kernel - Re: [PATCH] powerpc/powernv: Add kernel cmdline parameter to disable imc

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Message-Id: <87sheoby7c.fsf@linux.vnet.ibm.com>
Date:   Thu, 12 Oct 2017 18:51:51 +1100
From:   Stewart Smith <stewart@...ux.vnet.ibm.com>
To:     Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        maddy@...ux.vnet.ibm.com, hemant@...ux.vnet.ibm.com
Subject: Re: [PATCH] powerpc/powernv: Add kernel cmdline parameter to disable imc

Anju T Sudhakar <anju@...ux.vnet.ibm.com> writes:
> On Wednesday 11 October 2017 01:55 AM, Stewart Smith wrote:
>> Michael Ellerman <mpe@...erman.id.au> writes:
>>> Anju T Sudhakar <anju@...ux.vnet.ibm.com> writes:
>>>
>>>> Add a kernel command line parameter option to disable In-Memory Collection
>>>> (IMC) counters and add documentation. This helps in debug.
>>> I'd really rather we didn't. Do we *really* need this?
>>>
>>> We don't have command line parameters to disable any of the other ~20
>>> PMUs, why is this one special?
>
> This one is really helpful in debugging, incase if we want to proceed 
> without nest counters  OR
> core counters . But if we have the facility to do the same from 
> petitboot, its fine.

https://patchwork.ozlabs.org/patch/824497/ (skiboot patch) should do the
same thing, right? That means we come up with them off (as we should
have from the start) and if you don't use the PMUs then the ucode won't
be started.

-- 
Stewart Smith
OPAL Architect, IBM.