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

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Message-Id: <69dfcb10-2d7d-f6d3-3bb6-34ef6676b6b1@linux.vnet.ibm.com>
Date:   Thu, 12 Oct 2017 13:35:05 +0530
From:   Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
To:     Stewart Smith <stewart@...ux.vnet.ibm.com>,
        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,
        hemant@...ux.vnet.ibm.com
Subject: Re: [PATCH] powerpc/powernv: Add kernel cmdline parameter to disable
 imc



On Thursday 12 October 2017 01:21 PM, Stewart Smith wrote:
> 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,

Thats right. With that skiboot patch, IMC will be paused at start.