coresight: etm3x: Always set tracer's device mode on target CPU

The ETMv3 driver shares the same issue as ETMv4 regarding race
conditions when accessing the device mode.

This commit applies the same fix: ensuring that the device mode is
modified only by the target CPU to eliminate race conditions across
CPUs.

Fixes: 22fd532eaa0c ("coresight: etm3x: adding operation mode for etm_enable()")
Reviewed-by: Mike Leach <mike.leach@linaro.org>
Tested-by: James Clark <james.clark@linaro.org>
Signed-off-by: Leo Yan <leo.yan@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20251111-arm_coresight_power_management_fix-v6-3-f55553b6c8b3@arm.com

diff --git a/drivers/hwtracing/coresight/coresight-etm3x-core.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
index 45630a1cd32fbd05ec8b2a6979f0174cacce365e..a5e809589d3e382acde24ee457e94e5dcb18ea35 100644 (file)
--- a/drivers/hwtracing/coresight/coresight-etm3x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
@@ -439,13 +439,26 @@ struct etm_enable_arg {
        int rc;
 };
 
-static void etm_enable_hw_smp_call(void *info)
+static void etm_enable_sysfs_smp_call(void *info)
 {
        struct etm_enable_arg *arg = info;
+       struct coresight_device *csdev;
 
        if (WARN_ON(!arg))
                return;
+
+       csdev = arg->drvdata->csdev;
+       if (!coresight_take_mode(csdev, CS_MODE_SYSFS)) {
+               /* Someone is already using the tracer */
+               arg->rc = -EBUSY;
+               return;
+       }
+
        arg->rc = etm_enable_hw(arg->drvdata);
+
+       /* The tracer didn't start */
+       if (arg->rc)
+               coresight_set_mode(csdev, CS_MODE_DISABLED);
 }
 
 static int etm_cpu_id(struct coresight_device *csdev)
@@ -465,16 +478,26 @@ static int etm_enable_perf(struct coresight_device *csdev,
                           struct coresight_path *path)
 {
        struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+       int ret;
 
        if (WARN_ON_ONCE(drvdata->cpu != smp_processor_id()))
                return -EINVAL;
 
+       if (!coresight_take_mode(csdev, CS_MODE_PERF))
+               return -EBUSY;
+
        /* Configure the tracer based on the session's specifics */
        etm_parse_event_config(drvdata, event);
        drvdata->traceid = path->trace_id;
 
        /* And enable it */
-       return etm_enable_hw(drvdata);
+       ret = etm_enable_hw(drvdata);
+
+       /* Failed to start tracer; roll back to DISABLED mode */
+       if (ret)
+               coresight_set_mode(csdev, CS_MODE_DISABLED);
+
+       return ret;
 }
 
 static int etm_enable_sysfs(struct coresight_device *csdev, struct coresight_path *path)
@@ -494,7 +517,7 @@ static int etm_enable_sysfs(struct coresight_device *csdev, struct coresight_pat
        if (cpu_online(drvdata->cpu)) {
                arg.drvdata = drvdata;
                ret = smp_call_function_single(drvdata->cpu,
-                                              etm_enable_hw_smp_call, &arg, 1);
+                                              etm_enable_sysfs_smp_call, &arg, 1);
                if (!ret)
                        ret = arg.rc;
                if (!ret)
@@ -517,12 +540,6 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event,
                      enum cs_mode mode, struct coresight_path *path)
 {
        int ret;
-       struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
-
-       if (!coresight_take_mode(csdev, mode)) {
-               /* Someone is already using the tracer */
-               return -EBUSY;
-       }
 
        switch (mode) {
        case CS_MODE_SYSFS:
@@ -535,17 +552,12 @@ static int etm_enable(struct coresight_device *csdev, struct perf_event *event,
                ret = -EINVAL;
        }
 
-       /* The tracer didn't start */
-       if (ret)
-               coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
-
        return ret;
 }
 
-static void etm_disable_hw(void *info)
+static void etm_disable_hw(struct etm_drvdata *drvdata)
 {
        int i;
-       struct etm_drvdata *drvdata = info;
        struct etm_config *config = &drvdata->config;
        struct coresight_device *csdev = drvdata->csdev;
 
@@ -567,6 +579,15 @@ static void etm_disable_hw(void *info)
                "cpu: %d disable smp call done\n", drvdata->cpu);
 }
 
+static void etm_disable_sysfs_smp_call(void *info)
+{
+       struct etm_drvdata *drvdata = info;
+
+       etm_disable_hw(drvdata);
+
+       coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
+}
+
 static void etm_disable_perf(struct coresight_device *csdev)
 {
        struct etm_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
@@ -588,6 +609,8 @@ static void etm_disable_perf(struct coresight_device *csdev)
 
        CS_LOCK(drvdata->csa.base);
 
+       coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
+
        /*
         * perf will release trace ids when _free_aux()
         * is called at the end of the session
@@ -612,7 +635,8 @@ static void etm_disable_sysfs(struct coresight_device *csdev)
         * Executing etm_disable_hw on the cpu whose ETM is being disabled
         * ensures that register writes occur when cpu is powered.
         */
-       smp_call_function_single(drvdata->cpu, etm_disable_hw, drvdata, 1);
+       smp_call_function_single(drvdata->cpu, etm_disable_sysfs_smp_call,
+                                drvdata, 1);
 
        spin_unlock(&drvdata->spinlock);
        cpus_read_unlock();
@@ -652,9 +676,6 @@ static void etm_disable(struct coresight_device *csdev,
                WARN_ON_ONCE(mode);
                return;
        }
-
-       if (mode)
-               coresight_set_mode(csdev, CS_MODE_DISABLED);
 }
 
 static const struct coresight_ops_source etm_source_ops = {