linux-kernel - Re: [PATCH 1/8] perf/arm-cmn: Refactor node ID handling. Again.

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Message-ID: <eeb1eb1c-2e94-4110-a0ff-75efd0794c8e@arm.com>
Date: Tue, 27 Aug 2024 14:51:25 +0100
From: Robin Murphy <robin.murphy@....com>
To: Ilkka Koskinen <ilkka@...amperecomputing.com>
Cc: will@...nel.org, mark.rutland@....com,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/8] perf/arm-cmn: Refactor node ID handling. Again.

On 24/08/2024 2:00 am, Ilkka Koskinen wrote:
[...]
>> static struct arm_cmn_node *arm_cmn_node_to_xp(const struct arm_cmn *cmn,
>>                            const struct arm_cmn_node *dn)
>> {
>> -    struct arm_cmn_nodeid nid = arm_cmn_nid(cmn, dn->id);
>> -    int xp_idx = cmn->mesh_x * nid.y + nid.x;
>> +    int id = dn->id >> (dn->portid_bits + dn->deviceid_bits);
>> +    int bits = arm_cmn_xyidbits(cmn);
>> +    int x = id > bits;
>                    ^^^
> 
> Instead of comparison, shouldn't that be bit shift?

Oh dear indeed... and of course the effects of that would only show up 
on hardware configurations I don't have. Good catch, thanks!

Cheers,
Robin.