linux-kernel - Re: [PATCH] coresight: STM: Balance enable/disable

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Date:   Fri, 13 Jan 2017 17:11:39 +0000
From:   Suzuki K Poulose <Suzuki.Poulose@....com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Chunyan Zhang <zhang.chunyan@...aro.org>,
        Pratik Patel <pratikp@...eaurora.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "# 4 . 7" <stable@...r.kernel.org>
Subject: Re: [PATCH] coresight: STM: Balance enable/disable

On 13/01/17 16:48, Mathieu Poirier wrote:
> On 10 January 2017 at 04:21, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>> The stm is automatically enabled when an application sets the policy
>> via ->link() call back by using coresight_enable(), which keeps the
>> refcount of the current users of the STM. However, the unlink() callback
>> issues stm_disable() directly, which leaves the STM turned off, without
>> the coresight layer knowing about it. This prevents any further uses
>> of the STM hardware as the coresight layer still thinks the STM is
>> turned on and doesn't issue an stm_enable(). Even manually enabling
>> the STM via sysfs can't really enable the hw.
>>
...
>>
>> This patch balances the unlink operation by using the coresight_disable(),
>> keeping the coresight layer in sync with the hardware state.
>>
>> Fixes: commit 237483aa5cf43 ("coresight: stm: adding driver for CoreSight STM component")
>> Cc: Pratik Patel <pratikp@...eaurora.org>
>> Cc: Mathieu Poirier <mathieu.poirier@...aro.org>
>> Cc: Chunyan Zhang <zhang.chunyan@...aro.org>
>> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
>> Cc: stable@...r.kernel.org # 4.7+
>> Reported-by: Robert Walker <robert.walker@....com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
>> ---
>>  drivers/hwtracing/coresight/coresight-stm.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c
>> index 3524452..57b7330 100644
>> --- a/drivers/hwtracing/coresight/coresight-stm.c
>> +++ b/drivers/hwtracing/coresight/coresight-stm.c
>> @@ -356,7 +356,7 @@ static void stm_generic_unlink(struct stm_data *stm_data,
>>         if (!drvdata || !drvdata->csdev)
>>                 return;
>>
>> -       stm_disable(drvdata->csdev, NULL);
>> +       coresight_disable(drvdata->csdev);
>>  }
>>
>>  static phys_addr_t
>
> Applied - thanks,

Mathieu, Greg,

I think this should go into 4.10 (either way, as fix in this cycle or via stable after the release). I think
it would be easier if it goes in as fix during one of these rc cycle.

Please let me know your thoughts.

Suzuki

> Mathieu
>
>> --
>> 2.7.4
>>