The Coresight TMC-ETR SG mode could be unsafe on a platform where
the ETR is not properly connected to account for READ operations.
We use a DT node property to indicate if the system is safe.
This patch also provides a command line parameter to "force"
the use of SG mode to override the firmware information.
Cc: Mathieu Poirier <mathieu.poir...@linaro.org>
Cc: Mike Leach <mike.le...@linaro.org>
Signed-off-by: Suzuki K Poulose <suzuki.poul...@arm.com>
---
Hi
This is more of a debug patch for people who may want to
test their platform without too much of hacking. I am not
too keen on pushing this patch in.
---
Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++
drivers/hwtracing/coresight/coresight-tmc.c | 7 ++++++-
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt
b/Documentation/admin-guide/kernel-parameters.txt
index 11fc28e..03b51c3 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -675,6 +675,14 @@
Enable/disable the CPU sampling based debugging.
0: default value, disable debugging
1: enable debugging at boot time
+ coresight_tmc.etr_force_sg
+ [ARM, ARM64]
+ Format: <bool>
+ Force using the TMC ETR builtin scatter-gather mode
+ even when it may be unsafe to use.
+ Default : 0, do not force using the builtin SG mode.
+ 1, Allow using the SG, ignoring the firmware
+ provided information.
cpuidle.off=1 [CPU_IDLE]
disable the cpuidle sub-system
diff --git a/drivers/hwtracing/coresight/coresight-tmc.c
b/drivers/hwtracing/coresight/coresight-tmc.c
index e38379c..c7bc681 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.c
+++ b/drivers/hwtracing/coresight/coresight-tmc.c
@@ -20,6 +20,7 @@
#include <linux/err.h>
#include <linux/fs.h>
#include <linux/miscdevice.h>
+#include <linux/module.h>
#include <linux/property.h>
#include <linux/uaccess.h>
#include <linux/slab.h>
@@ -33,6 +34,8 @@
#include "coresight-priv.h"
#include "coresight-tmc.h"
+static bool etr_force_sg;
+
void tmc_wait_for_tmcready(struct tmc_drvdata *drvdata)
{
/* Ensure formatter, unformatter and hardware fifo are empty */
@@ -307,7 +310,8 @@ const struct attribute_group *coresight_tmc_groups[] = {
static inline bool tmc_etr_can_use_sg(struct tmc_drvdata *drvdata)
{
- return fwnode_property_present(drvdata->dev->fwnode, "scatter-gather");
+ return etr_force_sg ||
+ fwnode_property_present(drvdata->dev->fwnode, "scatter-gather");
}
/* Detect and initialise the capabilities of a TMC ETR */
@@ -482,3 +486,4 @@ static struct amba_driver tmc_driver = {
.id_table = tmc_ids,
};
builtin_amba_driver(tmc_driver);
+module_param(etr_force_sg, bool, 0);
--
2.7.4
