[PATCH V6 0/3] coresight: etm: Make cycle count threshold user configurable

[PATCH V6 0/3] coresight: etm: Make cycle count threshold user configurable

[Anshuman Khandual]

This series makes ETM TRCCCCTRL based 'cc_threshold' user configurable via
the perf event attribute. But first, this implements an errata work around
affecting ETM TRCIDR3.CCITMIN value on certain cpus, overriding the field.

This series applies on coresight/for-next/queue.

Cc: Catalin Marinas <catalin.marinas@arm.com> 
Cc: Will Deacon <will@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com> 
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org

Changes in V6:

- Renamed etm4_core_reads_wrong_ccitmin() as etm4_fixup_wrong_ccitmin()
- Moved drvdata->ccitmin fixup inside etm4_fixup_wrong_ccitmin()

Changes in V5:

https://lore.kernel.org/all/20230821045216.641499-1-anshuman.khandual@arm.com/
https://lore.kernel.org/all/20230915093649.435163-1-anshuman.khandual@arm.com/

- Replaced 'where as' with single word 'whereas'
- Reworked 'cc_threshold' fallback to ETM_CYC_THRESHOLD_DEFAULT

Changes in V4:

https://lore.kernel.org/all/20230818112051.594986-1-anshuman.khandual@arm.com/

- Fixed a typo s/rangess/ranges,
- Renamed etm4_work_around_wrong_ccitmin() as etm4_core_reads_wrong_ccitmin()
- Moved drvdata->ccitmin value check for 256 inside etm4_core_reads_wrong_ccitmin()
- Moved the comment inside etm4_core_reads_wrong_ccitmin()

Changes in V3:

https://lore.kernel.org/all/20230811034600.944386-1-anshuman.khandual@arm.com/

- Added errata work around affecting TRCIDR3.CCITMIN
- Split the document update into a separate patch

Changes in V2:

https://lore.kernel.org/all/20230808074533.380537-1-anshuman.khandual@arm.com/

- s/treshhold/threshold

Changes in V1:

https://lore.kernel.org/all/20230804044720.1478900-1-anshuman.khandual@arm.com/

Anshuman Khandual (3):
  coresight: etm: Override TRCIDR3.CCITMIN on errata affected cpus
  coresight: etm: Make cycle count threshold user configurable
  Documentation: coresight: Add cc_threshold tunable

 Documentation/arch/arm64/silicon-errata.rst   | 10 ++++
 Documentation/trace/coresight/coresight.rst   |  4 ++
 .../hwtracing/coresight/coresight-etm-perf.c  |  2 +
 .../coresight/coresight-etm4x-core.c          | 46 ++++++++++++++++++-
 4 files changed, 60 insertions(+), 2 deletions(-)

-- 
2.25.1


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[PATCH V6 1/3] coresight: etm: Override TRCIDR3.CCITMIN on errata affected cpus

[Anshuman Khandual]

This work arounds errata 1490853 on Cortex-A76, and Neoverse-N1, errata
1491015 on Cortex-A77, errata 1502854 on Cortex-X1, and errata 1619801 on
Neoverse-V1, based affected cpus, where software read for TRCIDR3.CCITMIN
field in ETM gets an wrong value.

If software uses the value returned by the TRCIDR3.CCITMIN register field,
then it will limit the range which could be used for programming the ETM.
In reality, the ETM could be programmed with a much smaller value than what
is indicated by the TRCIDR3.CCITMIN field and still function correctly.

If software reads the TRCIDR3.CCITMIN register field, corresponding to the
instruction trace counting minimum threshold, observe the value 0x100 or a
minimum cycle count threshold of 256. The correct value should be 0x4 or a
minimum cycle count threshold of 4.

This work arounds the problem via storing 4 in drvdata->ccitmin on affected
systems where the TRCIDR3.CCITMIN has been 256, thus preserving cycle count
threshold granularity.

These errata information has been updated in arch/arm64/silicon-errata.rst,
but without their corresponding configs because these have been implemented
directly in the driver.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-doc@vger.kernel.org
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 Documentation/arch/arm64/silicon-errata.rst   | 10 +++++
 .../coresight/coresight-etm4x-core.c          | 37 +++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/Documentation/arch/arm64/silicon-errata.rst b/Documentation/arch/arm64/silicon-errata.rst
index e96f057ea2a0..8f1be5da68b7 100644
--- a/Documentation/arch/arm64/silicon-errata.rst
+++ b/Documentation/arch/arm64/silicon-errata.rst
@@ -115,6 +115,10 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A76      | #1463225        | ARM64_ERRATUM_1463225       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A76      | #1490853        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A77      | #1491015        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A77      | #1508412        | ARM64_ERRATUM_1508412       |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A710     | #2119858        | ARM64_ERRATUM_2119858       |
@@ -125,6 +129,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A715     | #2645198        | ARM64_ERRATUM_2645198       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-X1       | #1502854        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-X2       | #2119858        | ARM64_ERRATUM_2119858       |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-X2       | #2224489        | ARM64_ERRATUM_2224489       |
@@ -133,6 +139,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N1     | #1349291        | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Neoverse-N1     | #1490853        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N1     | #1542419        | ARM64_ERRATUM_1542419       |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N2     | #2139208        | ARM64_ERRATUM_2139208       |
@@ -141,6 +149,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N2     | #2253138        | ARM64_ERRATUM_2253138       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Neoverse-V1     | #1619801        | N/A                         |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | MMU-500         | #841119,826419  | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | MMU-600         | #1076982,1209401| N/A                         |
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 77b0271ce6eb..9619d9d0bbb1 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1150,6 +1150,41 @@ static void cpu_detect_trace_filtering(struct etmv4_drvdata *drvdata)
 	drvdata->trfcr = trfcr;
 }
 
+/*
+ * The following errata on applicable cpu ranges, affect the CCITMIN filed
+ * in TCRIDR3 register. Software read for the field returns 0x100 limiting
+ * the cycle threshold granularity, whereas the right value should have
+ * been 0x4, which is well supported in the hardware.
+ */
+static struct midr_range etm_wrong_ccitmin_cpus[] = {
+	/* Erratum #1490853 - Cortex-A76 */
+	MIDR_RANGE(MIDR_CORTEX_A76, 0, 0, 4, 0),
+	/* Erratum #1490853 - Neoverse-N1 */
+	MIDR_RANGE(MIDR_NEOVERSE_N1, 0, 0, 4, 0),
+	/* Erratum #1491015 - Cortex-A77 */
+	MIDR_RANGE(MIDR_CORTEX_A77, 0, 0, 1, 0),
+	/* Erratum #1502854 - Cortex-X1 */
+	MIDR_REV(MIDR_CORTEX_X1, 0, 0),
+	/* Erratum #1619801 - Neoverse-V1 */
+	MIDR_REV(MIDR_NEOVERSE_V1, 0, 0),
+	{},
+};
+
+static void etm4_fixup_wrong_ccitmin(struct etmv4_drvdata *drvdata)
+{
+	/*
+	 * Erratum affected cpus will read 256 as the minimum
+	 * instruction trace cycle counting threshold whereas
+	 * the correct value should be 4 instead. Override the
+	 * recorded value for 'drvdata->ccitmin' to workaround
+	 * this problem.
+	 */
+	if (is_midr_in_range_list(read_cpuid_id(), etm_wrong_ccitmin_cpus)) {
+		if (drvdata->ccitmin == 256)
+			drvdata->ccitmin = 4;
+	}
+}
+
 static void etm4_init_arch_data(void *info)
 {
 	u32 etmidr0;
@@ -1214,6 +1249,8 @@ static void etm4_init_arch_data(void *info)
 	etmidr3 = etm4x_relaxed_read32(csa, TRCIDR3);
 	/* CCITMIN, bits[11:0] minimum threshold value that can be programmed */
 	drvdata->ccitmin = FIELD_GET(TRCIDR3_CCITMIN_MASK, etmidr3);
+	etm4_fixup_wrong_ccitmin(drvdata);
+
 	/* EXLEVEL_S, bits[19:16] Secure state instruction tracing */
 	drvdata->s_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_S_MASK, etmidr3);
 	drvdata->config.s_ex_level = drvdata->s_ex_level;
-- 
2.25.1


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[PATCH V6 2/3] coresight: etm: Make cycle count threshold user configurable

[Anshuman Khandual]

Cycle counting is enabled, when requested and supported but with a default
threshold value ETM_CYC_THRESHOLD_DEFAULT i.e 0x100 getting into TRCCCCTLR,
representing the minimum interval between cycle count trace packets.

This makes cycle threshold user configurable, from the user space via perf
event attributes. Although it falls back using ETM_CYC_THRESHOLD_DEFAULT,
in case no explicit request. As expected it creates a sysfs file as well.

/sys/bus/event_source/devices/cs_etm/format/cc_threshold

New 'cc_threshold' uses 'event->attr.config3' as no more space is available
in 'event->attr.config1' or 'event->attr.config2'.

Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c   | 2 ++
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 9 +++++++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 5ca6278baff4..09f75dffae60 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -68,6 +68,7 @@ PMU_FORMAT_ATTR(preset,		"config:0-3");
 PMU_FORMAT_ATTR(sinkid,		"config2:0-31");
 /* config ID - set if a system configuration is selected */
 PMU_FORMAT_ATTR(configid,	"config2:32-63");
+PMU_FORMAT_ATTR(cc_threshold,	"config3:0-11");
 
 
 /*
@@ -101,6 +102,7 @@ static struct attribute *etm_config_formats_attr[] = {
 	&format_attr_preset.attr,
 	&format_attr_configid.attr,
 	&format_attr_branch_broadcast.attr,
+	&format_attr_cc_threshold.attr,
 	NULL,
 };
 
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 9619d9d0bbb1..5b6a878a2ac5 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -644,7 +644,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
 	struct etmv4_config *config = &drvdata->config;
 	struct perf_event_attr *attr = &event->attr;
 	unsigned long cfg_hash;
-	int preset;
+	int preset, cc_threshold;
 
 	/* Clear configuration from previous run */
 	memset(config, 0, sizeof(struct etmv4_config));
@@ -667,7 +667,12 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
 	if (attr->config & BIT(ETM_OPT_CYCACC)) {
 		config->cfg |= TRCCONFIGR_CCI;
 		/* TRM: Must program this for cycacc to work */
-		config->ccctlr = ETM_CYC_THRESHOLD_DEFAULT;
+		cc_threshold = attr->config3 & ETM_CYC_THRESHOLD_MASK;
+		if (!cc_threshold)
+			cc_threshold = ETM_CYC_THRESHOLD_DEFAULT;
+		if (cc_threshold < drvdata->ccitmin)
+			cc_threshold = drvdata->ccitmin;
+		config->ccctlr = cc_threshold;
 	}
 	if (attr->config & BIT(ETM_OPT_TS)) {
 		/*
-- 
2.25.1


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[PATCH V6 3/3] Documentation: coresight: Add cc_threshold tunable

[Anshuman Khandual]

This updates config option to include 'cc_threshold' tunable value.

Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: James Clark <james.clark@arm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: coresight@lists.linaro.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Reviewed by: Mike Leach <mike.leach@linaro.org>
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
 Documentation/trace/coresight/coresight.rst | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst
index 4a71ea6cb390..ce55adb80b82 100644
--- a/Documentation/trace/coresight/coresight.rst
+++ b/Documentation/trace/coresight/coresight.rst
@@ -624,6 +624,10 @@ They are also listed in the folder /sys/bus/event_source/devices/cs_etm/format/
    * - timestamp
      - Session local version of the system wide setting: :ref:`ETMv4_MODE_TIMESTAMP
        <coresight-timestamp>`
+   * - cc_threshold
+     - Cycle count threshold value. If nothing is provided here or the provided value is 0, then the
+       default value i.e 0x100 will be used. If provided value is less than minimum cycles threshold
+       value, as indicated via TRCIDR3.CCITMIN, then the minimum value will be used instead.
 
 How to use the STM module
 -------------------------
-- 
2.25.1


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