[PATCH v11 11/27] coresight: etm4x: Hook CPU PM callbacks

Leo Yan
2026-05-01T16:48:49Z

Add a helper etm4_pm_save_needed() to detect if need save context for
self-hosted PM mode and hook pm_save_disable() and pm_restore_enable()
callbacks through etm4_cs_pm_ops structure. With this, ETMv4 PM
save/restore is integrated into the core layer's CPU PM.

Organize etm4_cs_ops and etm4_cs_pm_ops together for more readable.

The CPU PM notifier in the ETMv4 driver is no longer needed, remove it
along with its registration and unregistration code.

Reviewed-by: James Clark <james.clark@linaro.org>
Tested-by: James Clark <james.clark@linaro.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Tested-by: Jie Gan <jie.gan@oss.qualcomm.com>
Signed-off-by: Leo Yan <leo.yan@arm.com>
---
drivers/hwtracing/coresight/coresight-etm4x-core.c | 73 +++++++---------------
1 file changed, 23 insertions(+), 50 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index a776ebb3b2b0360c99a8dadacfde4c2303dd59d6..64bdc1b18b916b83fc063eb541193e0acfa741ee 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -1191,11 +1191,6 @@ static const struct coresight_ops_source etm4_source_ops = {
.pause_perf = etm4_pause_perf,
};

-static const struct coresight_ops etm4_cs_ops = {
- .trace_id = coresight_etm_get_trace_id,
- .source_ops = &etm4_source_ops,
-};
-
static bool cpu_supports_sysreg_trace(void)
{
u64 dfr0 = read_sysreg_s(SYS_ID_AA64DFR0_EL1);
@@ -1849,6 +1844,11 @@ static int etm4_dying_cpu(unsigned int cpu)
return 0;
}

+static inline bool etm4_pm_save_needed(struct etmv4_drvdata *drvdata)
+{
+ return !!drvdata->save_state;
+}
+
static int __etm4_cpu_save(struct etmv4_drvdata *drvdata)
{
int i, ret = 0;
@@ -1991,11 +1991,12 @@ static int __etm4_cpu_save(struct etmv4_drvdata *drvdata)
return ret;
}

-static int etm4_cpu_save(struct etmv4_drvdata *drvdata)
+static int etm4_cpu_save(struct coresight_device *csdev)
{
+ struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
int ret = 0;

- if (pm_save_enable != PARAM_PM_SAVE_SELF_HOSTED)
+ if (!etm4_pm_save_needed(drvdata))
return 0;

/*
@@ -2108,47 +2109,27 @@ static void __etm4_cpu_restore(struct etmv4_drvdata *drvdata)
etm4_cs_lock(drvdata, csa);
}

-static void etm4_cpu_restore(struct etmv4_drvdata *drvdata)
+static void etm4_cpu_restore(struct coresight_device *csdev)
{
- if (pm_save_enable != PARAM_PM_SAVE_SELF_HOSTED)
+ struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
+
+ if (!etm4_pm_save_needed(drvdata))
return;

if (coresight_get_mode(drvdata->csdev))
__etm4_cpu_restore(drvdata);
}

-static int etm4_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd,
- void *v)
-{
- struct etmv4_drvdata *drvdata;
- unsigned int cpu = smp_processor_id();
-
- if (!etmdrvdata[cpu])
- return NOTIFY_OK;
-
- drvdata = etmdrvdata[cpu];
-
- if (WARN_ON_ONCE(drvdata->cpu != cpu))
- return NOTIFY_BAD;
-
- switch (cmd) {
- case CPU_PM_ENTER:
- if (etm4_cpu_save(drvdata))
- return NOTIFY_BAD;
- break;
- case CPU_PM_EXIT:
- case CPU_PM_ENTER_FAILED:
- etm4_cpu_restore(drvdata);
- break;
- default:
- return NOTIFY_DONE;
- }
-
- return NOTIFY_OK;
-}
+static const struct coresight_ops etm4_cs_ops = {
+ .trace_id = coresight_etm_get_trace_id,
+ .source_ops = &etm4_source_ops,
+};

-static struct notifier_block etm4_cpu_pm_nb = {
- .notifier_call = etm4_cpu_pm_notify,
+static const struct coresight_ops etm4_cs_pm_ops = {
+ .trace_id = coresight_etm_get_trace_id,
+ .source_ops = &etm4_source_ops,
+ .pm_save_disable = etm4_cpu_save,
+ .pm_restore_enable = etm4_cpu_restore,
};

/* Setup PM. Deals with error conditions and counts */
@@ -2156,16 +2137,12 @@ static int __init etm4_pm_setup(void)
{
int ret;

- ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb);
- if (ret)
- return ret;
-
ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING,
"arm/coresight4:starting",
etm4_starting_cpu, etm4_dying_cpu);

if (ret)
- goto unregister_notifier;
+ return ret;

ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
"arm/coresight4:online",
@@ -2179,15 +2156,11 @@ static int __init etm4_pm_setup(void)

/* failed dyn state - remove others */
cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
-
-unregister_notifier:
- cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
return ret;
}

static void etm4_pm_clear(void)
{
- cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
if (hp_online) {
cpuhp_remove_state_nocalls(hp_online);
@@ -2239,7 +2212,7 @@ static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg)

desc.type = CORESIGHT_DEV_TYPE_SOURCE;
desc.subtype.source_subtype = CORESIGHT_DEV_SUBTYPE_SOURCE_PROC;
- desc.ops = &etm4_cs_ops;
+ desc.ops = etm4_pm_save_needed(drvdata) ? &etm4_cs_pm_ops : &etm4_cs_ops;
desc.pdata = pdata;
desc.dev = dev;
desc.groups = coresight_etmv4_groups;

--
2.34.1