[PATCH 0/3] coresight: Fix miscellaneous problems with CLAIM tags

[PATCH 0/3] coresight: Fix miscellaneous problems with CLAIM tags

[Mathieu Poirier]

This set addresses 3 problems observed with the CLAIM tag feature.  The first
patch adds support for CLAIM tags to the ETB10 drivers.  The second and third
patch deal with releasing the tags on ETF and ETM3x devices.

Review and testing would be appreciated.

Regards,
Mathieu

Mathieu Poirier (3):
  coresight: etb10: Add support for CLAIM tag
  coresight: etf: Release CLAIM tag after disabling the HW
  coresight: etm3x: Release CLAIM tag when operated from perf

 drivers/hwtracing/coresight/coresight-etb10.c   | 23 +++++++++++++++++------
 drivers/hwtracing/coresight/coresight-etm3x.c   |  2 ++
 drivers/hwtracing/coresight/coresight-tmc-etf.c |  2 +-
 3 files changed, 20 insertions(+), 7 deletions(-)

-- 
2.7.4

[PATCH 1/3] coresight: etb10: Add support for CLAIM tag

[Mathieu Poirier]

Following in the footstep of what was done for other CoreSight devices,
add CLAIM tag support to ETB10 in order to synchronise access to the
HW between the kernel and an external agent.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etb10.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etb10.c b/drivers/hwtracing/coresight/coresight-etb10.c
index 824be0c5f592..105782ea64c7 100644
--- a/drivers/hwtracing/coresight/coresight-etb10.c
+++ b/drivers/hwtracing/coresight/coresight-etb10.c
@@ -136,6 +136,11 @@ static void __etb_enable_hw(struct etb_drvdata *drvdata)
 
 static int etb_enable_hw(struct etb_drvdata *drvdata)
 {
+	int rc = coresight_claim_device(drvdata->base);
+
+	if (rc)
+		return rc;
+
 	__etb_enable_hw(drvdata);
 	return 0;
 }
@@ -223,7 +228,7 @@ static int etb_enable(struct coresight_device *csdev, u32 mode, void *data)
 	return 0;
 }
 
-static void etb_disable_hw(struct etb_drvdata *drvdata)
+static void __etb_disable_hw(struct etb_drvdata *drvdata)
 {
 	u32 ffcr;
 
@@ -313,6 +318,13 @@ static void etb_dump_hw(struct etb_drvdata *drvdata)
 	CS_LOCK(drvdata->base);
 }
 
+static void etb_disable_hw(struct etb_drvdata *drvdata)
+{
+	__etb_disable_hw(drvdata);
+	etb_dump_hw(drvdata);
+	coresight_disclaim_device(drvdata->base);
+}
+
 static void etb_disable(struct coresight_device *csdev)
 {
 	struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -323,7 +335,6 @@ static void etb_disable(struct coresight_device *csdev)
 	/* Disable the ETB only if it needs to */
 	if (drvdata->mode != CS_MODE_DISABLED) {
 		etb_disable_hw(drvdata);
-		etb_dump_hw(drvdata);
 		drvdata->mode = CS_MODE_DISABLED;
 	}
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
@@ -402,7 +413,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 
 	capacity = drvdata->buffer_depth * ETB_FRAME_SIZE_WORDS;
 
-	etb_disable_hw(drvdata);
+	__etb_disable_hw(drvdata);
 	CS_UNLOCK(drvdata->base);
 
 	/* unit is in words, not bytes */
@@ -510,7 +521,7 @@ static unsigned long etb_update_buffer(struct coresight_device *csdev,
 		handle->head = (cur * PAGE_SIZE) + offset;
 		to_read = buf->nr_pages << PAGE_SHIFT;
 	}
-	etb_enable_hw(drvdata);
+	__etb_enable_hw(drvdata);
 	CS_LOCK(drvdata->base);
 
 	return to_read;
@@ -534,9 +545,9 @@ static void etb_dump(struct etb_drvdata *drvdata)
 
 	spin_lock_irqsave(&drvdata->spinlock, flags);
 	if (drvdata->mode == CS_MODE_SYSFS) {
-		etb_disable_hw(drvdata);
+		__etb_disable_hw(drvdata);
 		etb_dump_hw(drvdata);
-		etb_enable_hw(drvdata);
+		__etb_enable_hw(drvdata);
 	}
 	spin_unlock_irqrestore(&drvdata->spinlock, flags);
 
-- 
2.7.4

[PATCH 2/3] coresight: etf: Release CLAIM tag after disabling the HW

[Mathieu Poirier]

This patch rectifies the sequence of events in function
tmc_etb_disable_hw() by disabling the HW first and then releasing the
CLAIM tag.  Otherwise we could be corrupting the configuration done by an
external agent that would have claimed the device after we have released
it.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-tmc-etf.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
index 5864ac55e275..a5f053f2db2c 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
@@ -86,8 +86,8 @@ static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
 
 static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
 {
-	coresight_disclaim_device(drvdata->base);
 	__tmc_etb_disable_hw(drvdata);
+	coresight_disclaim_device(drvdata->base);
 }
 
 static void __tmc_etf_enable_hw(struct tmc_drvdata *drvdata)
-- 
2.7.4

[PATCH 3/3] coresight: etm3x: Release CLAIM tag when operated from perf

[Mathieu Poirier]

This patch deals with the release of the CLAIM tag when the ETM is
operated from perf.  Otherwise the tag is left asserted and subsequent
requests to use the device fail.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm3x.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
index fd5c4cca7db5..000796394662 100644
--- a/drivers/hwtracing/coresight/coresight-etm3x.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x.c
@@ -603,6 +603,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
 	 */
 	etm_set_pwrdwn(drvdata);
 
+	coresight_disclaim_device_unlocked(drvdata->base);
+
 	CS_LOCK(drvdata->base);
 }
 
-- 
2.7.4

Re: [PATCH 1/3] coresight: etb10: Add support for CLAIM tag

[Suzuki K Poulose]

Hi Mathieu,

On 05/11/2018 22:26, Mathieu Poirier wrote:
> Following in the footstep of what was done for other CoreSight devices,
> add CLAIM tag support to ETB10 in order to synchronise access to the
> HW between the kernel and an external agent.
> 

Thanks for spotting this. Somehow I missed the etb10 in the original
series.

> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>

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

Re: [PATCH 2/3] coresight: etf: Release CLAIM tag after disabling the HW

[Suzuki K Poulose]

On 05/11/2018 22:26, Mathieu Poirier wrote:
> This patch rectifies the sequence of events in function
> tmc_etb_disable_hw() by disabling the HW first and then releasing the
> CLAIM tag.  Otherwise we could be corrupting the configuration done by an
> external agent that would have claimed the device after we have released
> it.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>   drivers/hwtracing/coresight/coresight-tmc-etf.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> index 5864ac55e275..a5f053f2db2c 100644
> --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c
> +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c
> @@ -86,8 +86,8 @@ static void __tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
>   
>   static void tmc_etb_disable_hw(struct tmc_drvdata *drvdata)
>   {
> -	coresight_disclaim_device(drvdata->base);
>   	__tmc_etb_disable_hw(drvdata);
> +	coresight_disclaim_device(drvdata->base);
>   }
>   

Well spotted.

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

Re: [PATCH 3/3] coresight: etm3x: Release CLAIM tag when operated from perf

[leo.yan]

Hi Mathieu,

On Mon, Nov 05, 2018 at 03:26:30PM -0700, Mathieu Poirier wrote:
> This patch deals with the release of the CLAIM tag when the ETM is
> operated from perf.  Otherwise the tag is left asserted and subsequent
> requests to use the device fail.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>  drivers/hwtracing/coresight/coresight-etm3x.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
> index fd5c4cca7db5..000796394662 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> @@ -603,6 +603,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
>  	 */
>  	etm_set_pwrdwn(drvdata);
>  
> +	coresight_disclaim_device_unlocked(drvdata->base);
> +

Just remind, this isn't consistent with the sequency in function
etm_disable_hw(), which has the reversed sequence between
etm_set_pwrdwn() and coresight_disclaim_device_unlocked().

Not sure which one sequence is more suitable, at the first glance,
accessing register after pwrdwn related operation might have risk for
deadlock?

Thanks,
Leo Yan

>  	CS_LOCK(drvdata->base);
>  }
>  
> -- 
> 2.7.4
> 

Re: [PATCH 3/3] coresight: etm3x: Release CLAIM tag when operated from perf

[Suzuki K Poulose]

Leo,

On 07/11/2018 03:23, leo.yan@linaro.org wrote:
> Hi Mathieu,
> 
> On Mon, Nov 05, 2018 at 03:26:30PM -0700, Mathieu Poirier wrote:
>> This patch deals with the release of the CLAIM tag when the ETM is
>> operated from perf.  Otherwise the tag is left asserted and subsequent
>> requests to use the device fail.
>>
>> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>> ---
>>   drivers/hwtracing/coresight/coresight-etm3x.c | 2 ++
>>   1 file changed, 2 insertions(+)
>>
>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
>> index fd5c4cca7db5..000796394662 100644
>> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
>> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
>> @@ -603,6 +603,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
>>   	 */
>>   	etm_set_pwrdwn(drvdata);
>>   
>> +	coresight_disclaim_device_unlocked(drvdata->base);
>> +


> 
> Just remind, this isn't consistent with the sequency in function
> etm_disable_hw(), which has the reversed sequence between
> etm_set_pwrdwn() and coresight_disclaim_device_unlocked().
> 
> Not sure which one sequence is more suitable, at the first glance,
> accessing register after pwrdwn related operation might have risk for
> deadlock?

Good point.

I assume that the CLAIMSET/CLR registers are in the same power domain as
the LAR (Software Lock Access register) accessed below. But I will
confirm this with the architect. Based on the response, we could
streamline both the sequences.

Suzuki

> 
> Thanks,
> Leo Yan
> 
>>   	CS_LOCK(drvdata->base);
>>   }
>>   
>> -- 
>> 2.7.4
>>

Re: [PATCH 3/3] coresight: etm3x: Release CLAIM tag when operated from perf

[Mathieu Poirier]

On Thu, 8 Nov 2018 at 02:49, Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>
> Leo,
>
> On 07/11/2018 03:23, leo.yan@linaro.org wrote:
> > Hi Mathieu,
> >
> > On Mon, Nov 05, 2018 at 03:26:30PM -0700, Mathieu Poirier wrote:
> >> This patch deals with the release of the CLAIM tag when the ETM is
> >> operated from perf.  Otherwise the tag is left asserted and subsequent
> >> requests to use the device fail.
> >>
> >> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> >> ---
> >>   drivers/hwtracing/coresight/coresight-etm3x.c | 2 ++
> >>   1 file changed, 2 insertions(+)
> >>
> >> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
> >> index fd5c4cca7db5..000796394662 100644
> >> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> >> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
> >> @@ -603,6 +603,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
> >>       */
> >>      etm_set_pwrdwn(drvdata);
> >>
> >> +    coresight_disclaim_device_unlocked(drvdata->base);
> >> +
>
>
> >
> > Just remind, this isn't consistent with the sequency in function
> > etm_disable_hw(), which has the reversed sequence between
> > etm_set_pwrdwn() and coresight_disclaim_device_unlocked().
> >
> > Not sure which one sequence is more suitable, at the first glance,
> > accessing register after pwrdwn related operation might have risk for
> > deadlock?
>
> Good point.
>
> I assume that the CLAIMSET/CLR registers are in the same power domain as
> the LAR (Software Lock Access register) accessed below. But I will
> confirm this with the architect. Based on the response, we could
> streamline both the sequences.

In this case etm_set_pwrdwn() sets bit 0 of ETMCR, which disables the
ETM.  That being said the Embedded Trace Macrocell Architecture
Specification (ID101211) mentions in section 3.5.1 that despite ETMCR
bit 0 being set to 1, it is always possible to write to the claim set
registers.  As such I moved the release of the claim tag in function
etm_disable_hw() below etm_set_pwrdwn() in the second revision of this
set [1].

[1]. https://lkml.org/lkml/2018/11/8/223

>
> Suzuki
>
> >
> > Thanks,
> > Leo Yan
> >
> >>      CS_LOCK(drvdata->base);
> >>   }
> >>
> >> --
> >> 2.7.4
> >>