On 28/04/2026 13:18, James Clark wrote:
ETE registers are always system registers so it's highly unlikely there will be an implementation that preserves them on CPU power down. Also the ETE DT binding never documented "arm,coresight-loses-context-with-cpu" so nobody would have legitimately been able to use that binding to fix it.
Fix it by hard coding the setting for ETE and add a warning if the user tried to use the module parameter. Don't add a warning if loses-context-with-cpu is present in the DT as it's not a documented binding anyway. etm4_init_pm_save() needs to happen after drvdata is initialised so etm4x_is_ete() can be called.
This fixes the following error when using Coresight with ACPI on the FVP which supports CPU PM:
coresight ete0: External agent took claim tag WARNING: drivers/hwtracing/coresight/coresight-core.c:248 at coresight_disclaim_device_unlocked+0xe0/0xe8, CPU#0: perf/117
Fixes: 35e1c9163e02 ("coresight: ete: Add support for ETE tracing") Signed-off-by: James Clark james.clark@linaro.org
drivers/hwtracing/coresight/coresight-etm4x-core.c | 41 +++++++++++++++------- 1 file changed, 29 insertions(+), 12 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c index d565a73f0042..a7fb680dd383 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c @@ -56,10 +56,11 @@ MODULE_PARM_DESC(boot_enable, "Enable tracing on boot"); #define PARAM_PM_SAVE_NEVER 1 /* never save any state */ #define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */ +/* Save option for ETM4. ETE ignores this option and always saves */ static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE; module_param(pm_save_enable, int, 0444); MODULE_PARM_DESC(pm_save_enable,
- "Save/restore state on power down: 1 = never, 2 = self-hosted");
- "Save/restore state on power down: 1 = never, 2 = self-hosted. ETM4 only.");
static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; static void etm4_set_default_config(struct etmv4_config *config); @@ -1365,6 +1366,30 @@ static void etm4_fixup_wrong_ccitmin(struct etmv4_drvdata *drvdata) } } +static int etm4_init_pm_save(struct device *dev, struct etmv4_drvdata *drvdata) +{
- if (etm4x_is_ete(drvdata)) {
/** Always do PM save for ETE. It always uses system registers* which will be lost on CPU power down.*/pm_save_enable = PARAM_PM_SAVE_SELF_HOSTED;
Should we do this instead based on if the ETM/ETE is accessed via sys instructions ? That would cover all implementations?
Suzuki
- } else if (pm_save_enable == PARAM_PM_SAVE_FIRMWARE) {
pm_save_enable = coresight_loses_context_with_cpu(dev) ?PARAM_PM_SAVE_SELF_HOSTED : PARAM_PM_SAVE_NEVER;- }
- if (pm_save_enable != PARAM_PM_SAVE_NEVER) {
drvdata->save_state = devm_kmalloc(dev,sizeof(struct etmv4_save_state),GFP_KERNEL);if (!drvdata->save_state)return -ENOMEM;- }
- return 0;
+}
- static void etm4_init_arch_data(void *info) { u32 etmidr0;
@@ -2247,6 +2272,9 @@ static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg) return -ENOMEM; etm4_set_default(&drvdata->config);
- ret = etm4_init_pm_save(dev, drvdata);
- if (ret)
return ret;pdata = coresight_get_platform_data(dev); if (IS_ERR(pdata)) @@ -2305,17 +2333,6 @@ static int etm4_probe(struct device *dev) if (ret) return ret;
- if (pm_save_enable == PARAM_PM_SAVE_FIRMWARE)
pm_save_enable = coresight_loses_context_with_cpu(dev) ?PARAM_PM_SAVE_SELF_HOSTED : PARAM_PM_SAVE_NEVER;- if (pm_save_enable != PARAM_PM_SAVE_NEVER) {
drvdata->save_state = devm_kmalloc(dev,sizeof(struct etmv4_save_state), GFP_KERNEL);if (!drvdata->save_state)return -ENOMEM;- }
- raw_spin_lock_init(&drvdata->spinlock);
drvdata->cpu = coresight_get_cpu(dev);