linux-kernel - Re: [PATCH v5 6/7] powerpc/powernv: generic nest pmu event functions

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Date:	Thu, 23 Jul 2015 14:52:15 +0530
From:	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>
CC:	Daniel Axtens <dja@...ens.net>, linux-kernel@...r.kernel.org,
	Stephane Eranian <eranian@...gle.com>,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org,
	Anshuman Khandual <khandual@...ux.vnet.ibm.com>
Subject: Re: [PATCH v5 6/7] powerpc/powernv: generic nest pmu event functions



On Thursday 23 July 2015 02:34 PM, Michael Ellerman wrote:
> On Thu, 2015-07-23 at 12:14 +0530, Madhavan Srinivasan wrote:
>> On Wednesday 22 July 2015 10:26 AM, Daniel Axtens wrote:
>>>> +static void p8_nest_read_counter(struct perf_event *event)
>>>> +{
>>>> +	uint64_t *addr;
>>>> +	u64 data = 0;
>>> You've got a u64 and a uint64_t, and then...
>>>> +
>>>> +	addr = (u64 *)event->hw.event_base;
>>> ... you cast to event_base to a u64 pointer, which you assign to a
>>> uint64_t pointer.
>>>> +	data = __be64_to_cpu(*addr);
>>> And now you dereference the pointer.
>>> Could you just have:
>>>     data = __be64_to_cpu(*event->hw.event_base);
>>>> +	local64_set(&event->hw.prev_count, data);
>>>> +}
>>>> +
>>>> +static void p8_nest_perf_event_update(struct perf_event *event)
>>>> +{
>>>> +	u64 counter_prev, counter_new, final_count;
>>>> +	uint64_t *addr;
>>>> +
>>>> +	addr = (uint64_t *)event->hw.event_base;
>>> Here at least the cast type is the same as the type of addr, but again,
>>> why do you need the different types, and why local variable?
>> Damn sorry, copy paste errors. When I added debug prints i messed
>> the type case in both the functions. I will make them as uint64_t.
> No please use u64/u32 etc. Most code in powerpc does and I prefer them.
>
> cheers
Ok Sure. Will use only u64 and u32.

Thanks
maddy

>

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