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SubjectRe: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks
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On 19/04/16 16:45, Mathieu Poirier wrote:
> On 19 April 2016 at 07:19, Suzuki K Poulose <Suzuki.Poulose@arm.com> wrote:
>> On 12/04/16 18:54, Mathieu Poirier wrote:
>>>
>>> Moving tmc_drvdata::enable to a local_t mode. That way the
>>> sink interface is aware of it's orgin and the foundation for
>>> mutual exclusion between the sysFS and Perf interface can be
>>> laid out.
>>>
>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>> ---
>>> drivers/hwtracing/coresight/coresight-tmc-etf.c | 28
>>> ++++++++++++++++++-------
>>> drivers/hwtracing/coresight/coresight-tmc-etr.c | 24
>>> ++++++++++++++++-----
>>> drivers/hwtracing/coresight/coresight-tmc.h | 4 ++--
>>> 3 files changed, 42 insertions(+), 14 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c
>>> b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>>> index 7cb287ef7b9e..5908000e1ae0 100644
>>> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
>>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
>>> @@ -110,6 +110,7 @@ static int tmc_enable_etf_sink(struct coresight_device
>>> *csdev, u32 mode)
>>> {
>>> bool allocated = false;
>>> char *buf = NULL;
>>> + u32 val;
>>> unsigned long flags;
>>> struct tmc_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>>>
>>> @@ -146,6 +147,15 @@ fast_path:
>>> return -EBUSY;
>>> }
>>>
>>> + val = local_xchg(&drvdata->mode, mode);
>>> + /*
>>> + * In sysFS mode we can have multiple writers per sink. Since
>>> this
>>> + * sink is already enabled no memory is needed and the HW need not
>>> be
>>> + * touched.
>>> + */
>>> + if (val == CS_MODE_SYSFS)
>>> + goto out;
>>> +
>>
>>
>> We are not dropping the spinlock in this case. Are we ?
>
> Definitely - thanks for pointing that out.
>
>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-tmc.h
>>> b/drivers/hwtracing/coresight/coresight-tmc.h
>>> index 80096fa75326..821bdf150ac9 100644
>>> --- a/drivers/hwtracing/coresight/coresight-tmc.h
>>> +++ b/drivers/hwtracing/coresight/coresight-tmc.h
>>> @@ -100,7 +100,7 @@ enum tmc_mem_intf_width {
>>> * @paddr: DMA start location in RAM.
>>> * @vaddr: virtual representation of @paddr.
>>> * @size: @buf size.
>>> - * @enable: this TMC is being used.
>>> + * @mode: how this TMC is being used.
>>> * @config_type: TMC variant, must be of type @tmc_config_type.
>>> * @trigger_cntr: amount of words to store after a trigger.
>>> */
>>> @@ -116,7 +116,7 @@ struct tmc_drvdata {
>>> dma_addr_t paddr;
>>> void __iomem *vaddr;
>>> u32 size;
>>> - bool enable;
>>> + local_t mode;
>>
>>
>> Since we always deal with the mode under the spinlock, do we really need
>> this to
>> be local_t ? Or do we plan to get rid of the lock ?
>
> You are correct, using a local_t variable isn't strictly needed here. But:
>
> 1) It greatly simplifies the code.

+1

> 2) I'm really hoping one day we can do without the spinlocks, though I
> don't know when that will happen.
>
> Get back to me if you're resolute on switching the local_t to a normal type.

No, leave it as it is, as you said, it does simplify the code.

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