From: Michael Ellerman <mpe@ellerman.id.au>
To: Anju T Sudhakar <anju@linux.vnet.ibm.com>,
Stewart Smith <stewart@linux.vnet.ibm.com>,
Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
ego@linux.vnet.ibm.com, bsingharora@gmail.com,
benh@kernel.crashing.org, paulus@samba.org, anton@samba.org,
sukadev@linux.vnet.ibm.com, mikey@neuling.org, dja@axtens.net,
eranian@google.com, Hemant Kumar <hemant@linux.vnet.ibm.com>
Subject: Re: [PATCH v6 03/11] powerpc/powernv: Detect supported IMC units and its events
Date: Thu, 13 Apr 2017 21:43:22 +1000 [thread overview]
Message-ID: <87o9w08rdx.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <50380e09-9f5e-d2d4-ce91-26c616b2ce5e@linux.vnet.ibm.com>
Anju T Sudhakar <anju@linux.vnet.ibm.com> writes:
> On Thursday 06 April 2017 02:07 PM, Stewart Smith wrote:
>> Madhavan Srinivasan <maddy@linux.vnet.ibm.com> writes:
>>> --- a/arch/powerpc/platforms/powernv/opal-imc.c
>>> +++ b/arch/powerpc/platforms/powernv/opal-imc.c
>>> @@ -33,6 +33,388 @@
>> <snip>
>>> +static void imc_pmu_setup(struct device_node *parent)
>>> +{
>>> + struct device_node *child;
>>> + int pmu_count = 0, rc = 0;
>>> + const struct property *pp;
>>> +
>>> + if (!parent)
>>> + return;
>>> +
>>> + /* Setup all the IMC pmus */
>>> + for_each_child_of_node(parent, child) {
>>> + pp = of_get_property(child, "compatible", NULL);
>>> + if (pp) {
>>> + /*
>>> + * If there is a node with a "compatible" field,
>>> + * that's a PMU node
>>> + */
>>> + rc = imc_pmu_create(child, pmu_count);
>>> + if (rc)
>>> + return;
>>> + pmu_count++;
>>> + }
>>> + }
>>> +}
>> This doesn't strike me as the right kind of structure, the presence of a
>> compatible property really just says "hey, there's this device and it's
>> compatible with these ways of accessing it".
>>
>> I'm guessing the idea behind having imc-nest-offset/size in a top level
>> node is because it's common to everything under it and the aim is to not
>> blow up the device tree to be enormous.
>>
>> So why not go after each ibm,imc-counters-nest compatible node under the
>> top level ibm,opal-in-memory-counters node? (i'm not convinced that
>> having ibm,ibmc-counters-nest versus ibm,imc-counters-core and
>> ibm,imc-counters-thread as I see in the dts is correct though, as
>> they're all accessed exactly the same way?)
>
> The idea here is, we have one directory which contains common events
> information for nest(same incase of core and thread), and one directory
> for each nest(/core/thread) pmu.
> So while parsing we need to make sure that the node which we are parsing
> is the pmu node, not the node which contains the common event
> information. We use the "compatible" property here for that purpose.
> Because we don't have a compatible property for the node which contains
> events info.
That's a really bad hack.
You can use the compatible property to detect the node you're looking
for, but you need to look at the *value* of the property and check it's
what you expect. Just checking that it's there is fragile.
cheers
next prev parent reply other threads:[~2017-04-13 11:43 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-03 14:54 [PATCH v6 00/11] IMC Instrumentation Support Madhavan Srinivasan
2017-04-03 14:54 ` [PATCH v6 01/11] powerpc/powernv: Data structure and macros definitions Madhavan Srinivasan
2017-04-04 1:48 ` Daniel Axtens
2017-04-05 4:22 ` Madhavan Srinivasan
2017-04-06 8:07 ` Stewart Smith
2017-04-06 8:39 ` Stewart Smith
2017-04-03 14:54 ` [PATCH v6 02/11] powerpc/powernv: Autoload IMC device driver module Madhavan Srinivasan
2017-04-04 0:58 ` Daniel Axtens
2017-04-05 6:34 ` Madhavan Srinivasan
2017-04-04 1:48 ` Daniel Axtens
2017-04-05 6:36 ` Madhavan Srinivasan
2017-04-06 7:04 ` Stewart Smith
2017-04-03 14:55 ` [PATCH v6 03/11] powerpc/powernv: Detect supported IMC units and its events Madhavan Srinivasan
2017-04-04 1:41 ` Daniel Axtens
2017-04-05 12:29 ` Madhavan Srinivasan
2017-04-06 8:37 ` Stewart Smith
2017-04-06 9:33 ` Anju T Sudhakar
2017-04-13 11:43 ` Michael Ellerman [this message]
2017-04-17 8:08 ` Anju T Sudhakar
2017-04-03 14:55 ` [PATCH v6 04/11] powerpc/perf: Add event attribute and group to IMC pmus Madhavan Srinivasan
2017-04-04 2:11 ` Daniel Axtens
2017-04-06 6:43 ` Madhavan Srinivasan
2017-04-03 14:55 ` [PATCH v6 05/11] powerpc/perf: Generic imc pmu event functions Madhavan Srinivasan
2017-04-04 3:55 ` Daniel Axtens
2017-04-03 14:55 ` [PATCH v6 06/11] powerpc/perf: IMC pmu cpumask and cpu hotplug support Madhavan Srinivasan
2017-04-04 4:33 ` Daniel Axtens
2017-04-06 8:04 ` Madhavan Srinivasan
2017-04-03 14:55 ` [PATCH v6 07/11] powerpc/powernv: Core IMC events detection Madhavan Srinivasan
2017-04-03 14:55 ` [PATCH v6 08/11] powerpc/perf: PMU functions for Core IMC and hotplugging Madhavan Srinivasan
2017-04-03 14:55 ` [PATCH v6 09/11] powerpc/powernv: Thread IMC events detection Madhavan Srinivasan
2017-04-03 14:55 ` [PATCH v6 10/11] powerpc/perf: Thread IMC PMU functions Madhavan Srinivasan
2017-04-03 14:55 ` [PATCH v6 11/11] powerpc/perf: Thread imc cpuhotplug support Madhavan Srinivasan
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