linux-kernel - Re: [PATCH] coresight: tmc: Cleanup operation mode handling

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Message-ID: <b693447b-e89c-d4ea-bc57-6c447d688055@arm.com>
Date:   Mon, 19 Sep 2016 17:59:04 +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>,
        Venkatesh Vivekanandan <venkatesh.vivekanandan@...adcom.com>
Subject: Re: [PATCH] coresight: tmc: Cleanup operation mode handling

On 16/09/16 18:07, Mathieu Poirier wrote:
> On 14 September 2016 at 07:53, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>> The mode of operation of the TMC tracked in drvdata->mode is defined
>> as a local_t type. This is always checked and modified under the
>> drvdata->spinlock and hence we don't need local_t for it and the
>> unnecessary synchronisation instructions that comes with it. This
>> change makes the code a bit more cleaner.
>>
>> Also fixes the order in which we update the drvdata->mode to
>> CS_MODE_DISABLED. i.e, in tmc_disable_etX_sink we change the
>> mode to CS_MODE_DISABLED before invoking tmc_disable_etX_hw()
>> which in turn depends on the mode to decide whether to dump the
>> trace to a buffer.
>
> Thank you for the patch - just a few comments below.
>


>> @@ -194,17 +192,17 @@ static int tmc_enable_etf_sink_perf(struct coresight_device *csdev, u32 mode)
>>                 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 ETB/ETR is already operated
>>          * from sysFS.
>>          */
>> -       if (val != CS_MODE_DISABLED) {
>> +       if (drvdata->mode != CS_MODE_DISABLED) {
>>                 ret = -EINVAL;
>>                 goto out;
>>         }
>>
>> +       drvdata->mode = mode;
>
> Given the way tmc_enable_etf_sink_perf() is called in
> tmc_enable_etf_sink(), I think it is time to get rid of the 'mode'
> parameter - it doesn't do anything nowadays.  Same thing for
> tmc_enable_etf_sink_sysfs() and ETR.

Sure, makes sense. I will clean it up.

>> @@ -279,8 +277,8 @@ static void tmc_disable_etf_link(struct coresight_device *csdev,
>>                 return;
>>         }
>>
>> +       drvdata->mode = CS_MODE_DISABLED;
>>         tmc_etf_disable_hw(drvdata);
>> -       local_set(&drvdata->mode, CS_MODE_DISABLED);
>
> I think setting the mode should come after tmc_etf_disable_hw(), as it
> was before.

You're right, I will change it.


Thanks for the review. Will send the updated series soon.

Cheers
Suzuki
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