From: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org
[ Upstream commit 2d1a8bfb61ec0177343e99ebd745e3e4ceb0d0d5 ]
etm4_count keeps track of number of ETMv4 registered and on some systems, a race is observed on etm4_count variable which can lead to multiple calls to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls cpuhp_store_callbacks() which prevents multiple registrations of callbacks for a given state and due to this race, it returns -EBUSY leading to ETM probe failures like below.
coresight-etm4x: probe of 7040000.etm failed with error -16
This race can easily be triggered with async probe by setting probe type as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property "arm,coresight-loses-context-with-cpu".
Prevent this race by moving cpuhp callbacks to etm driver init since the cpuhp callbacks doesn't have to depend on the etm4_count and can be once setup during driver init. Similarly we move cpu_pm notifier registration to driver init and completely remove etm4_count usage. Also now we can use non cpuslocked version of cpuhp callbacks with this movement.
Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in probe() function") Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state machine") Suggested-by: Suzuki K Poulose suzuki.poulose@arm.com Tested-by: Stephen Boyd swboyd@chromium.org Reviewed-by: Stephen Boyd swboyd@chromium.org Reviewed-by: Suzuki K Poulose suzuki.poulose@arm.com Signed-off-by: Sai Prakash Ranjan saiprakash.ranjan@codeaurora.org Signed-off-by: Mathieu Poirier mathieu.poirier@linaro.org Link: https://lore.kernel.org/r/20200916191737.4001561-2-mathieu.poirier@linaro.or... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hwtracing/coresight/coresight-etm4x.c | 65 +++++++++---------- 1 file changed, 31 insertions(+), 34 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c index 6089c481f8f19..a970bd17edf8d 100644 --- a/drivers/hwtracing/coresight/coresight-etm4x.c +++ b/drivers/hwtracing/coresight/coresight-etm4x.c @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); MODULE_PARM_DESC(pm_save_enable, "Save/restore state on power down: 1 = never, 2 = self-hosted");
-/* The number of ETMv4 currently registered */ -static int etm4_count; static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; static void etm4_set_default_config(struct etmv4_config *config); static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, @@ -1394,28 +1392,25 @@ static struct notifier_block etm4_cpu_pm_nb = { .notifier_call = etm4_cpu_pm_notify, };
-/* Setup PM. Called with cpus locked. Deals with error conditions and counts */ -static int etm4_pm_setup_cpuslocked(void) +/* Setup PM. Deals with error conditions and counts */ +static int __init etm4_pm_setup(void) { int ret;
- if (etm4_count++) - return 0; - ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); if (ret) - goto reduce_count; + return ret;
- ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, - "arm/coresight4:starting", - etm4_starting_cpu, etm4_dying_cpu); + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING, + "arm/coresight4:starting", + etm4_starting_cpu, etm4_dying_cpu);
if (ret) goto unregister_notifier;
- ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, - "arm/coresight4:online", - etm4_online_cpu, NULL); + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, + "arm/coresight4:online", + etm4_online_cpu, NULL);
/* HP dyn state ID returned in ret on success */ if (ret > 0) { @@ -1424,21 +1419,15 @@ static int etm4_pm_setup_cpuslocked(void) }
/* failed dyn state - remove others */ - cpuhp_remove_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING); + cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
unregister_notifier: cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); - -reduce_count: - --etm4_count; return ret; }
-static void etm4_pm_clear(void) +static void __init etm4_pm_clear(void) { - if (--etm4_count != 0) - return; - cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); if (hp_online) { @@ -1491,22 +1480,12 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) if (!desc.name) return -ENOMEM;
- cpus_read_lock(); etmdrvdata[drvdata->cpu] = drvdata;
if (smp_call_function_single(drvdata->cpu, etm4_init_arch_data, drvdata, 1)) dev_err(dev, "ETM arch init failed\n");
- ret = etm4_pm_setup_cpuslocked(); - cpus_read_unlock(); - - /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ - if (ret) { - etmdrvdata[drvdata->cpu] = NULL; - return ret; - } - if (etm4_arch_supported(drvdata->arch) == false) { ret = -EINVAL; goto err_arch_supported; @@ -1553,7 +1532,6 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
err_arch_supported: etmdrvdata[drvdata->cpu] = NULL; - etm4_pm_clear(); return ret; }
@@ -1591,4 +1569,23 @@ static struct amba_driver etm4x_driver = { .probe = etm4_probe, .id_table = etm4_ids, }; -builtin_amba_driver(etm4x_driver); + +static int __init etm4x_init(void) +{ + int ret; + + ret = etm4_pm_setup(); + + /* etm4_pm_setup() does its own cleanup - exit on error */ + if (ret) + return ret; + + ret = amba_driver_register(&etm4x_driver); + if (ret) { + pr_err("Error registering etm4x driver\n"); + etm4_pm_clear(); + } + + return ret; +} +device_initcall(etm4x_init);