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

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Message-ID: <1603448595-22615-1-git-send-email-liuqi115@huawei.com>
Date:   Fri, 23 Oct 2020 18:23:15 +0800
From:   Qi Liu <liuqi115@...wei.com>
To:     <mathieu.poirier@...aro.org>, <suzuki.poulose@....com>,
        <Al.Grant@....com>, <mike.leach@...aro.org>
CC:     <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linuxarm@...wei.com>
Subject: [PATCH v3] coresight: etm4x: Modify core-commit of cpu to avoid the overflow of HiSilicon ETM

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@...wei.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