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From: Mark Rutland <mark.rutland@arm.com>
To: Ganapatrao Kulkarni <gklkml16@gmail.com>
Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@cavium.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Will Deacon <Will.Deacon@arm.com>,
	jnair@caviumnetworks.com,
	Robert Richter <Robert.Richter@cavium.com>,
	Vadim.Lomovtsev@cavium.com, Jan.Glauber@cavium.com
Subject: Re: [PATCH v4 2/2] ThunderX2: Add Cavium ThunderX2 SoC UNCORE PMU driver
Date: Mon, 21 May 2018 11:55:11 +0100	[thread overview]
Message-ID: <20180521105511.6ztjk5conf7lfaiz@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <CAKTKpr7Q7T9ZCTBi=LQR=XaAoihbBA3OKCO7yFobzNmR8EfyjQ@mail.gmail.com>

On Sat, May 05, 2018 at 12:16:13AM +0530, Ganapatrao Kulkarni wrote:
> On Thu, Apr 26, 2018 at 4:29 PM, Mark Rutland <mark.rutland@arm.com> wrote:
> > On Wed, Apr 25, 2018 at 02:30:47PM +0530, Ganapatrao Kulkarni wrote:

> >> + *
> >> + *  L3 Tile and DMC channel selection is through SMC call
> >> + *  SMC call arguments,
> >> + *   x0 = THUNDERX2_SMC_CALL_ID      (Vendor SMC call Id)
> >> + *   x1 = THUNDERX2_SMC_SET_CHANNEL  (Id to set DMC/L3C channel)
> >> + *   x2 = Node id
> >
> > How do we map Linux node IDs to the firmware's view of node IDs?
> >
> > I don't believe the two are necessarily the same -- Linux's node IDs are
> > a Linux-specific construct.
> 
> both are same, it is numa node id from ACPI/firmware.

I am very wary about assuming that the Linux nid will always be the same
as the ACPI node id.

For that to *potentially* be true, this driver should depend on
CONFIG_NUMA, NUMA must not be disabled on the command line, etc, or the
node id will always be NUMA_NO_NODE.

I would be *much* happier if we had an explicit mapping somewhere to the
ID the FW expects.

> > It would be much nicer if we could pass something based on the MPIDR,
> > which is a known HW construct, or if this implicitly affected the
> > current node.
> 
> IMO,  node id is sufficient.

I agree that *a* node ID is sufficient, I just don't think that we're
guaranteed to have the specific node ID the FW wants.

> > It would be vastly more sane for this to not be muxed at all. :/
> 
> i am helpless due to crappy hw design!

I'm certainly not blaming you for this! :)

I hope the HW designers don't make the same mistake in future, though...

Thanks,
Mark.

  parent reply	other threads:[~2018-05-21 10:55 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-25  9:00 [PATCH v4 0/2] Add ThunderX2 SoC Performance Monitoring Unit driver Ganapatrao Kulkarni
2018-04-25  9:00 ` [PATCH v4 1/2] perf: uncore: Adding documentation for ThunderX2 pmu uncore driver Ganapatrao Kulkarni
2018-04-26 20:55   ` Randy Dunlap
2018-04-27  4:49     ` Ganapatrao Kulkarni
2018-04-25  9:00 ` [PATCH v4 2/2] ThunderX2: Add Cavium ThunderX2 SoC UNCORE PMU driver Ganapatrao Kulkarni
2018-04-26 10:59   ` Mark Rutland
2018-05-04 18:46     ` Ganapatrao Kulkarni
2018-05-15 10:33       ` Ganapatrao Kulkarni
2018-05-21 10:37         ` Mark Rutland
2018-05-21 10:40           ` Mark Rutland
2018-05-21 12:42             ` Ganapatrao Kulkarni
2018-05-21 10:55       ` Mark Rutland [this message]
2018-05-21 12:34         ` Ganapatrao Kulkarni
2018-04-26 22:06   ` Kim Phillips
2018-04-27  9:30     ` Mark Rutland
2018-04-27 13:15       ` Kim Phillips
2018-04-27 14:37         ` Will Deacon
2018-04-27 15:46           ` Kim Phillips
2018-04-27 16:09             ` Will Deacon
2018-04-27 16:56               ` Kim Phillips
2018-05-01 11:54                 ` Will Deacon
2018-05-04  0:30                   ` Kim Phillips
2018-05-04 17:10                     ` Robin Murphy
2018-05-10  1:09                       ` Kim Phillips

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