linux-kernel - Re: [PATCH v2 3/4] coresight: etm3x: Deal with CLAIM tag before and after accessing HW

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Message-ID: <0928085c-cf9c-5437-2806-1b027ea428ff@arm.com>
Date:   Fri, 9 Nov 2018 18:06:11 +0000
From:   Suzuki K Poulose <suzuki.poulose@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Leo Yan <leo.yan@...aro.org>, coresight@...ts.linaro.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] coresight: etm3x: Deal with CLAIM tag before and
 after accessing HW

On 11/09/2018 05:59 PM, Mathieu Poirier wrote:
> On Thu, 8 Nov 2018 at 10:13, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>>
>> Hi,
>>
>> On 07/11/2018 23:08, Mathieu Poirier wrote:
>>> This patch moves access to the CLAIM tag so that no modification to the HW
>>> happens before and after the CLAIM operation has been carried.
>>>
>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
>>> ---
>>>    drivers/hwtracing/coresight/coresight-etm3x.c | 16 ++++++++--------
>>>    1 file changed, 8 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
>>> index fd5c4cca7db5..4f638d81a66a 100644
>>> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
>>> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
>>> @@ -363,15 +363,16 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
>>>
>>>        CS_UNLOCK(drvdata->base);
>>>
>>> +     rc = coresight_claim_device_unlocked(drvdata->base);
>>> +     if (rc)
>>> +             goto done;
>>> +
>>>        /* Turn engine on */
>>>        etm_clr_pwrdwn(drvdata);
>>>        /* Apply power to trace registers */
>>>        etm_set_pwrup(drvdata);
>>>        /* Make sure all registers are accessible */
>>>        etm_os_unlock(drvdata);
>>> -     rc = coresight_claim_device_unlocked(drvdata->base);
>>> -     if (rc)
>>> -             goto done;
>>>
>>>        etm_set_prog(drvdata);
>>>
>>> @@ -422,12 +423,11 @@ static int etm_enable_hw(struct etm_drvdata *drvdata)
>>>        etm_clr_prog(drvdata);
>>>
>>>    done:
>>> -     if (rc)
>>> -             etm_set_pwrdwn(drvdata);
>>>        CS_LOCK(drvdata->base);
>>>
>>> -     dev_dbg(drvdata->dev, "cpu: %d enable smp call done: %d\n",
>>> -             drvdata->cpu, rc);
>>> +     if (!rc)
>>> +             dev_dbg(drvdata->dev, "cpu: %d enable smp call done: %d\n",
>>> +                     drvdata->cpu, rc);
>>
>> Isn't it good to report the failure case too ? Anyway it is dev_dbg and
>> will be a useful info when we debug issues. Otherwise,
> 
> Simply removing the "if (!rc)" will do the trick.  Can I do the
> modification and add your tag or you prefer to see another revision?

I am fine with that change folded in, no need to respin it.

> 
>>
>> Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>


Cheers
Suzuki


>>
>>>        return rc;
>>>    }
>>>
>>> @@ -577,9 +577,9 @@ static void etm_disable_hw(void *info)
>>>        for (i = 0; i < drvdata->nr_cntr; i++)
>>>                config->cntr_val[i] = etm_readl(drvdata, ETMCNTVRn(i));
>>>
>>> +     etm_set_pwrdwn(drvdata);
>>>        coresight_disclaim_device_unlocked(drvdata->base);
>>>
>>> -     etm_set_pwrdwn(drvdata);
>>>        CS_LOCK(drvdata->base);
>>>
>>>        dev_dbg(drvdata->dev, "cpu: %d disable smp call done\n", drvdata->cpu);
>>>
>>