[PATCH v3] coresight: etm4x: Modify core-commit of cpu to avoid the overflow of HiSilicon ETM

[Qi Liu]

The ETM device can't keep up with the core pipeline when cpu core
is at full speed. This may cause overflow within core and its ETM.
This is a common phenomenon on ETM devices.

On HiSilicon Hip08 platform, a specific feature is added to set
core pipeline. So commit rate can be reduced manually to avoid ETM
overflow.

Signed-off-by: Qi Liu <liuqi115 at huawei.com>
---
Change since v1:
- add CONFIG_ETM4X_IMPDEF_FEATURE and CONFIG_ETM4X_IMPDEF_HISILICON
  to keep specific feature off platforms which don't use it.
Change since v2:
- remove some unused variable.

 drivers/hwtracing/coresight/Kconfig                | 18 ++++++++
 drivers/hwtracing/coresight/coresight-etm4x-core.c | 50 ++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
index c119824..9665d70 100644
--- a/drivers/hwtracing/coresight/Kconfig
+++ b/drivers/hwtracing/coresight/Kconfig
@@ -110,6 +110,24 @@ config CORESIGHT_SOURCE_ETM4X
 	  To compile this driver as a module, choose M here: the
 	  module will be called coresight-etm4x.

+config ETM4X_IMPDEF_FEATURE
+	bool "Control overflow impdef support in CoreSight ETM 4.x driver "
+	depends on CORESIGHT_SOURCE_ETM4X
+	help
+	  This control provides overflow implement define for CoreSight
+	  ETM 4.x tracer module which could not reduce commit race
+	  automatically, and could avoid overflow within ETM tracer module
+	  and its cpu core.
+
+config ETM4X_IMPDEF_HISILICON
+	bool "Control overflow impdef support in HiSilicon ETM 4.x driver "
+	depends on ETM4X_IMPDEF_FEATURE
+	help
+	  This control provides overflow implement define for HiSilicon
+	  ETM 4.x tracer module of Hip08 platform. Overflow within ETM
+	  tracer module and its cpu core can be avoided by reducing core
+	  commit manually.
+
 config CORESIGHT_STM
 	tristate "CoreSight System Trace Macrocell driver"
 	depends on (ARM && !(CPU_32v3 || CPU_32v4 || CPU_32v4T)) || ARM64
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index abd706b..35f4333 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -103,12 +103,61 @@ struct etm4_enable_arg {
 	int rc;
 };

+#ifdef CONFIG_ETM4X_IMPDEF_FEATURE
+
+#ifdef CONFIG_ETM4X_IMPDEF_HISILICON
+
+#define HISI_HIP08_CORE_COMMIT_CLEAR	0x3000
+#define HISI_HIP08_CORE_COMMIT_SHIFT	12
+static void etm4_hisi_config_core_commit(int flag)
+{
+	u64 val;
+
+	asm volatile("mrs %0,s3_1_c15_c2_5" : "=r"(val));
+	val &= ~HISI_HIP08_CORE_COMMIT_CLEAR;
+	val |= flag << HISI_HIP08_CORE_COMMIT_SHIFT;
+	asm volatile("msr s3_1_c15_c2_5,%0" : : "r"(val));
+}
+#else
+static void etm4_hisi_config_core_commit(int flag)
+{
+}
+#endif /* CONFIG_ETM4X_IMPDEF_HISILICON */
+
+static void etm4_enable_arch_specific(void)
+{
+	/*
+	 * If ETM device is HiSilicon ETM device, reduce the
+	 * core-commit to avoid ETM overflow.
+	 */
+	etm4_hisi_config_core_commit(1);
+}
+
+static void etm4_disable_arch_specific(void)
+{
+	/*
+	 * If ETM device is HiSilicon ETM device, resume the
+	 * core-commit after ETM trace is complete.
+	 */
+	etm4_hisi_config_core_commit(0);
+}
+#else
+static void etm4_enable_arch_specific(void)
+{
+}
+
+static void etm4_disable_arch_specific(void)
+{
+}
+#endif /* CONFIG_ETM4X_IMPDEF_FEATURE */
+
 static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
 {
 	int i, rc;
 	struct etmv4_config *config = &drvdata->config;
 	struct device *etm_dev = &drvdata->csdev->dev;

+	etm4_enable_arch_specific();
 	CS_UNLOCK(drvdata->base);

 	etm4_os_unlock(drvdata);
@@ -475,6 +524,7 @@ static void etm4_disable_hw(void *info)
 	struct device *etm_dev = &drvdata->csdev->dev;
 	int i;

+	etm4_disable_arch_specific();
 	CS_UNLOCK(drvdata->base);

 	if (!drvdata->skip_power_up) {
--
2.8.1