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Groups > linux.kernel > #1382499 > unrolled thread
| Started by | Suzuki K Poulose <Suzuki.Poulose@arm.com> |
|---|---|
| First post | 2016-04-19 15:20 +0200 |
| Last post | 2016-04-19 17:50 +0200 |
| Articles | 3 — 2 participants |
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Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks Suzuki K Poulose <Suzuki.Poulose@arm.com> - 2016-04-19 15:20 +0200
Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks Suzuki K Poulose <Suzuki.Poulose@arm.com> - 2016-04-19 17:50 +0200
Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks Mathieu Poirier <mathieu.poirier@linaro.org> - 2016-04-19 17:50 +0200
| From | Suzuki K Poulose <Suzuki.Poulose@arm.com> |
|---|---|
| Date | 2016-04-19 15:20 +0200 |
| Subject | Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks |
| Message-ID | <rpDJo-7sx-19@gated-at.bofh.it> |
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 ?
> /*
> * If drvdata::buf isn't NULL, memory was allocated for a previous
> * trace run but wasn't read. If so simply zero-out the memory.
> @@ -163,9 +173,9 @@ fast_path:
> }
>
> tmc_etb_enable_hw(drvdata);
> - drvdata->enable = true;
> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>
> +out:
> /* Free memory outside the spinlock if need be */
> if (!allocated && buf)
> kfree(buf);
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> index 6022ff26deba..8e6fe267195a 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
> @@ -85,6 +85,7 @@ static void tmc_etr_disable_hw(struct tmc_drvdata *drvdata)
> static int tmc_enable_etr_sink(struct coresight_device *csdev, u32 mode)
> {
> bool allocated = false;
> + u32 val;
> unsigned long flags;
> void __iomem *vaddr = NULL;
> dma_addr_t paddr;
> @@ -125,6 +126,15 @@ 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;
> +
Same as above, we should drop the locks in this case.
> @@ -140,9 +150,9 @@ fast_path:
> memset(drvdata->vaddr, 0, drvdata->size);
>
> tmc_etr_enable_hw(drvdata);
> - drvdata->enable = true;
> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>
> +out:
> /* Free memory outside the spinlock if need be */
> if (!allocated && vaddr)
> dma_free_coherent(drvdata->dev, drvdata->size, vaddr, paddr);
> @@ -153,6 +163,7 @@ fast_path:
> 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 ?
Suzuki
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| From | Suzuki K Poulose <Suzuki.Poulose@arm.com> |
|---|---|
| Date | 2016-04-19 17:50 +0200 |
| Message-ID | <rpG4y-Hd-3@gated-at.bofh.it> |
| In reply to | #1382499 |
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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| From | Mathieu Poirier <mathieu.poirier@linaro.org> |
|---|---|
| Date | 2016-04-19 17:50 +0200 |
| Subject | Re: [PATCH V2 09/15] coresight: tmc: adding mode of operation for link/sinks |
| Message-ID | <rpG4y-Hd-5@gated-at.bofh.it> |
| In reply to | #1382499 |
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.
>
>> /*
>> * If drvdata::buf isn't NULL, memory was allocated for a previous
>> * trace run but wasn't read. If so simply zero-out the memory.
>> @@ -163,9 +173,9 @@ fast_path:
>> }
>>
>> tmc_etb_enable_hw(drvdata);
>> - drvdata->enable = true;
>> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>>
>> +out:
>> /* Free memory outside the spinlock if need be */
>> if (!allocated && buf)
>> kfree(buf);
>
>
>> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> index 6022ff26deba..8e6fe267195a 100644
>> --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
>> @@ -85,6 +85,7 @@ static void tmc_etr_disable_hw(struct tmc_drvdata
>> *drvdata)
>> static int tmc_enable_etr_sink(struct coresight_device *csdev, u32 mode)
>> {
>> bool allocated = false;
>> + u32 val;
>> unsigned long flags;
>> void __iomem *vaddr = NULL;
>> dma_addr_t paddr;
>> @@ -125,6 +126,15 @@ 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;
>> +
>
>
> Same as above, we should drop the locks in this case.
>
>> @@ -140,9 +150,9 @@ fast_path:
>> memset(drvdata->vaddr, 0, drvdata->size);
>>
>> tmc_etr_enable_hw(drvdata);
>> - drvdata->enable = true;
>> spin_unlock_irqrestore(&drvdata->spinlock, flags);
>>
>> +out:
>> /* Free memory outside the spinlock if need be */
>> if (!allocated && vaddr)
>> dma_free_coherent(drvdata->dev, drvdata->size, vaddr,
>> paddr);
>> @@ -153,6 +163,7 @@ fast_path:
>
>
>> 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.
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.
Mathieu
>
> Suzuki
>
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