linux-kernel - Re: [PATCH V3 13/18] coresight: tmc: make sysFS and Perf mode mutually exclusive

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Message-ID: <571E2F16.3010706@arm.com>
Date:	Mon, 25 Apr 2016 15:52:06 +0100
From:	Suzuki K Poulose <Suzuki.Poulose@....com>
To:	Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 13/18] coresight: tmc: make sysFS and Perf mode
 mutually exclusive

On 25/04/16 15:48, Mathieu Poirier wrote:
> On 25 April 2016 at 08:32, Suzuki K Poulose <Suzuki.Poulose@....com> wrote:
>> On 22/04/16 18:14, Mathieu Poirier wrote:

>>> +       spin_lock_irqsave(&drvdata->spinlock, flags);
>>> +       if (drvdata->reading) {
>>> +               ret = -EINVAL;
>>> +               goto out;
>>> +       }
>>> +
>>> +       val = local_xchg(&drvdata->mode, mode);
>>> +       /*
>>> +        * In Perf mode there can be only one writer per sink.  There
>>> +        * is also no need to continue if the ETR is already operated
>>> +        * from sysFS.
>>> +        */
>>> +       if (val != CS_MODE_DISABLED) {
>>
>>
>> Could val be CS_MODE_PERF ? In other words, should we be checking :
>>          if (val == CS_MODE_SYSFS)  instead ?
>
> If we check for CS_MODE_SYSFS we also have to check for CS_MODE_PERF,
> which is two checks rather than a single one with the current
> solution.

I am confused now. The comment says, we want to check for sysfs mode and
don't continue in that case. So, we shouldn't be worried about PERF mode.

Suzuki