[PATCH v2 1/2] coresight: etm4x: Expose default timestamp source in sysfs

[PATCH v2 1/2] coresight: etm4x: Expose default timestamp source in sysfs

[German Gomez]

Add a new sysfs interface in /sys/bus/coresight/devices/etm<N>/ts_source
indicating the configured timestamp source when the ETM device driver
was probed.

The perf tool will use this information to detect if the trace data
timestamp matches the kernel time, enabling correlation of CoreSight
trace with perf events.

Suggested-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: German Gomez <german.gomez@arm.com>
Reviewed-by: Leo Yan <leo.yan@linaro.org>
---
v1:
    - https://lore.kernel.org/all/20220429123100.268059-2-german.gomez@arm.com/
v2:
    - Inline etmv4_to_ts_source() function.
    - Collect review tag from Leo.
---
 arch/arm64/include/asm/sysreg.h               |  1 +
 .../coresight/coresight-etm4x-sysfs.c         | 29 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 38508e507d73a..263a7bee06f9a 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -1146,6 +1146,7 @@
 #define SYS_MPIDR_SAFE_VAL	(BIT(31))
 
 #define TRFCR_ELx_TS_SHIFT		5
+#define TRFCR_ELx_TS_MASK		((0x3UL) << TRFCR_ELx_TS_SHIFT)
 #define TRFCR_ELx_TS_VIRTUAL		((0x1UL) << TRFCR_ELx_TS_SHIFT)
 #define TRFCR_ELx_TS_GUEST_PHYSICAL	((0x2UL) << TRFCR_ELx_TS_SHIFT)
 #define TRFCR_ELx_TS_PHYSICAL		((0x3UL) << TRFCR_ELx_TS_SHIFT)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
index a0640fa5c55bd..2a48827a4e135 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -2264,6 +2264,34 @@ static ssize_t cpu_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(cpu);
 
+static ssize_t ts_source_show(struct device *dev,
+			      struct device_attribute *attr,
+			      char *buf)
+{
+	int val;
+	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
+
+	if (!drvdata->trfcr) {
+		val = -1;
+		goto out;
+	}
+
+	switch (drvdata->trfcr & TRFCR_ELx_TS_MASK) {
+	case TRFCR_ELx_TS_VIRTUAL:
+	case TRFCR_ELx_TS_GUEST_PHYSICAL:
+	case TRFCR_ELx_TS_PHYSICAL:
+		val = FIELD_GET(TRFCR_ELx_TS_MASK, drvdata->trfcr);
+		break;
+	default:
+		val = -1;
+		break;
+	}
+
+out:
+	return sysfs_emit(buf, "%d\n", val);
+}
+static DEVICE_ATTR_RO(ts_source);
+
 static struct attribute *coresight_etmv4_attrs[] = {
 	&dev_attr_nr_pe_cmp.attr,
 	&dev_attr_nr_addr_cmp.attr,
@@ -2318,6 +2346,7 @@ static struct attribute *coresight_etmv4_attrs[] = {
 	&dev_attr_vmid_val.attr,
 	&dev_attr_vmid_masks.attr,
 	&dev_attr_cpu.attr,
+	&dev_attr_ts_source.attr,
 	NULL,
 };
 
-- 
2.25.1

[PATCH v2 2/2] coresight: etm4x: docs: Add documentation for 'ts_source' sysfs interface

[German Gomez]

Sync sysfs documentation pages to include the new ts_source (timestamp
source) interface.

Signed-off-by: German Gomez <german.gomez@arm.com>
---
v1:
    - https://lore.kernel.org/all/20220429123100.268059-3-german.gomez@arm.com/
v2:
    - Update Data, KernelVersion, and Contact fields (Date is
      tentative but likely).
---
 .../ABI/testing/sysfs-bus-coresight-devices-etm4x  |  8 ++++++++
 .../trace/coresight/coresight-etm4x-reference.rst  | 14 ++++++++++++++
 2 files changed, 22 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x
index 8e53a32f81505..520dd2e27eab3 100644
--- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x
+++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x
@@ -516,3 +516,11 @@ Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
 Description:	(Read) Returns the number of special conditional P1 right-hand keys
 		that the trace unit can use (0x194).  The value is taken
 		directly from the HW.
+
+What:		/sys/bus/coresight/devices/etm<N>/ts_source
+Date:		July 2022
+KernelVersion:	5.19
+Contact:	Mathieu Poirier <mathieu.poirier@linaro.org> or Suzuki K Poulose <suzuki.poulose@arm.com>
+Description:	(Read) When FEAT_TRF is implemented, value of TRFCR_ELx.TS used for
+		trace session. Otherwise -1 indicates an unknown time source. Check
+		trcidr0.tssize to see if a global timestamp is available.
diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst
index d25dfe86af9bf..f016c7c29429b 100644
--- a/Documentation/trace/coresight/coresight-etm4x-reference.rst
+++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst
@@ -71,6 +71,20 @@ the ‘TRC’ prefix.
 
 ----
 
+:File:            ``ts_source`` (ro)
+:Trace Registers: None.
+:Notes:
+    When FEAT_TRF is implemented, value of TRFCR_ELx.TS used for trace session. Otherwise -1
+    indicates an unknown time source. Check trcidr0.tssize to see if a global timestamp is
+    available.
+
+:Example:
+    ``$> cat ts_source``
+
+    ``$> 1``
+
+----
+
 :File:            ``addr_idx`` (rw)
 :Trace Registers: None.
 :Notes:
-- 
2.25.1

Re: [PATCH v2 2/2] coresight: etm4x: docs: Add documentation for 'ts_source' sysfs interface

[German Gomez]

Hi,

Thanks for your comments and review in the previous submission (and
sorry for not including a cover letter this time).

Do you want me to hold on this change, or update the corresponding
fields with new estimates?

Thanks,
German

On 03/05/2022 13:35, German Gomez wrote:
> Sync sysfs documentation pages to include the new ts_source (timestamp
> source) interface.
>
> Signed-off-by: German Gomez <german.gomez@arm.com>
> ---
> v1:
>     - https://lore.kernel.org/all/20220429123100.268059-3-german.gomez@arm.com/
> v2:
>     - Update Data, KernelVersion, and Contact fields (Date is
>       tentative but likely).
> ---
>  .../ABI/testing/sysfs-bus-coresight-devices-etm4x  |  8 ++++++++
>  .../trace/coresight/coresight-etm4x-reference.rst  | 14 ++++++++++++++
>  2 files changed, 22 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x
> index 8e53a32f81505..520dd2e27eab3 100644
> --- a/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x
> +++ b/Documentation/ABI/testing/sysfs-bus-coresight-devices-etm4x
> @@ -516,3 +516,11 @@ Contact:	Mathieu Poirier <mathieu.poirier@linaro.org>
>  Description:	(Read) Returns the number of special conditional P1 right-hand keys
>  		that the trace unit can use (0x194).  The value is taken
>  		directly from the HW.
> +
> +What:		/sys/bus/coresight/devices/etm<N>/ts_source
> +Date:		July 2022
> +KernelVersion:	5.19
> +Contact:	Mathieu Poirier <mathieu.poirier@linaro.org> or Suzuki K Poulose <suzuki.poulose@arm.com>
> +Description:	(Read) When FEAT_TRF is implemented, value of TRFCR_ELx.TS used for
> +		trace session. Otherwise -1 indicates an unknown time source. Check
> +		trcidr0.tssize to see if a global timestamp is available.
> diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst
> index d25dfe86af9bf..f016c7c29429b 100644
> --- a/Documentation/trace/coresight/coresight-etm4x-reference.rst
> +++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst
> @@ -71,6 +71,20 @@ the ‘TRC’ prefix.
>  
>  ----
>  
> +:File:            ``ts_source`` (ro)
> +:Trace Registers: None.
> +:Notes:
> +    When FEAT_TRF is implemented, value of TRFCR_ELx.TS used for trace session. Otherwise -1
> +    indicates an unknown time source. Check trcidr0.tssize to see if a global timestamp is
> +    available.
> +
> +:Example:
> +    ``$> cat ts_source``
> +
> +    ``$> 1``
> +
> +----
> +
>  :File:            ``addr_idx`` (rw)
>  :Trace Registers: None.
>  :Notes: