[PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

[PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

[Sai Prakash Ranjan]

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.

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>
Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
---

Changes in v2:
 * Rearrange cpuhp callbacks and move them to driver init (Suzuki K Poulose)

---
 drivers/hwtracing/coresight/coresight-etm4x.c | 51 ++++++++++---------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
index 6d7d2169bfb2..adb71987a1e3 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,
@@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(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",
@@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void)
 
 unregister_notifier:
 	cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
-
-reduce_count:
-	--etm4_count;
 	return ret;
 }
 
 static void 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) {
@@ -1498,22 +1487,12 @@ 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;
@@ -1560,7 +1539,6 @@ 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;
 }
 
@@ -1598,4 +1576,29 @@ 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;
+
+	cpus_read_lock();
+	ret = etm4_pm_setup_cpuslocked();
+	cpus_read_unlock();
+
+	/* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */
+	if (ret)
+		return ret;
+
+	ret = amba_driver_register(&etm4x_driver);
+	if (ret) {
+		pr_info("Error registering etm4x driver\n");
+		goto err_init;
+	}
+
+	return ret;
+
+err_init:
+	etm4_pm_clear();
+	return ret;
+}
+module_init(etm4x_init);
-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

[Stephen Boyd]

Quoting Sai Prakash Ranjan (2020-07-28 00:51:02)
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 6d7d2169bfb2..adb71987a1e3 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,
> @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void)

Is this only called from __init now? If so please mark it as __init
then.

>  {
>         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",
> @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void)
>  
>  unregister_notifier:
>         cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
> -
> -reduce_count:
> -       --etm4_count;
>         return ret;
>  }
>  
>  static void etm4_pm_clear(void)

This is __init too?

>  {
> -       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) {
> @@ -1598,4 +1576,29 @@ 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;
> +
> +       cpus_read_lock();
> +       ret = etm4_pm_setup_cpuslocked();
> +       cpus_read_unlock();
> +
> +       /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */
> +       if (ret)
> +               return ret;
> +
> +       ret = amba_driver_register(&etm4x_driver);
> +       if (ret) {
> +               pr_info("Error registering etm4x driver\n");

Use pr_err() please.

> +               goto err_init;
> +       }
> +
> +       return ret;
> +
> +err_init:

Why is this a goto?

> +       etm4_pm_clear();
> +       return ret;

Instead of just putting this in the if (ret) arm?

> +}
> +module_init(etm4x_init);

It was device_initcall before with builtin_amba_driver(), best to not
change that.

Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

[Sai Prakash Ranjan]

On 2020-07-28 13:59, Stephen Boyd wrote:
> Quoting Sai Prakash Ranjan (2020-07-28 00:51:02)
>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c 
>> b/drivers/hwtracing/coresight/coresight-etm4x.c
>> index 6d7d2169bfb2..adb71987a1e3 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,
>> @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void)
> 
> Is this only called from __init now? If so please mark it as __init
> then.
> 

Yes, will change it.

>>  {
>>         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",
>> @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void)
>> 
>>  unregister_notifier:
>>         cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
>> -
>> -reduce_count:
>> -       --etm4_count;
>>         return ret;
>>  }
>> 
>>  static void etm4_pm_clear(void)
> 
> This is __init too?
> 

Will change.

>>  {
>> -       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) {
>> @@ -1598,4 +1576,29 @@ 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;
>> +
>> +       cpus_read_lock();
>> +       ret = etm4_pm_setup_cpuslocked();
>> +       cpus_read_unlock();
>> +
>> +       /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on 
>> error */
>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = amba_driver_register(&etm4x_driver);
>> +       if (ret) {
>> +               pr_info("Error registering etm4x driver\n");
> 
> Use pr_err() please.
> 

Yes indeed, will change.

>> +               goto err_init;
>> +       }
>> +
>> +       return ret;
>> +
>> +err_init:
> 
> Why is this a goto?
> 
>> +       etm4_pm_clear();
>> +       return ret;
> 
> Instead of just putting this in the if (ret) arm?
> 

Will change.

>> +}
>> +module_init(etm4x_init);
> 
> It was device_initcall before with builtin_amba_driver(), best to not
> change that.

Sure.

I will wait to see if there are any more comments on this patch and then 
post a v3.
Thanks for the review Stephen.

Thanks,
Sai

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a 
member
of Code Aurora Forum, hosted by The Linux Foundation

Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

[Mike Leach]

Hi Sai,

On Tue, 28 Jul 2020 at 08:51, Sai Prakash Ranjan
<saiprakash.ranjan@codeaurora.org> wrote:
>
> 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.
>
> 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>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> ---
>
> Changes in v2:
>  * Rearrange cpuhp callbacks and move them to driver init (Suzuki K Poulose)
>
> ---
>  drivers/hwtracing/coresight/coresight-etm4x.c | 51 ++++++++++---------
>  1 file changed, 27 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c
> index 6d7d2169bfb2..adb71987a1e3 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,
> @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void)
>  {

consider renaming this to etm4_pm_setup() and handing any cpu locking
inside the function.
In the circumstances - as part of the driver init rather than probe it
may be sufficient to call the cpuhp_setup functions without the
_cpuslocked suffix and allow the calls to lock the cpus as they are
made.
i.e. cpuhp_setup_state_nocalls_cpuslocked() => cpuhp_setup_state_nocalls()

>         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",
> @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void)
>
>  unregister_notifier:
>         cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
> -
> -reduce_count:
> -       --etm4_count;
>         return ret;
>  }
>
>  static void 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) {
> @@ -1498,22 +1487,12 @@ 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;
> @@ -1560,7 +1539,6 @@ 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;
>  }
>
> @@ -1598,4 +1576,29 @@ 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;
> +
> +       cpus_read_lock();
> +       ret = etm4_pm_setup_cpuslocked();
> +       cpus_read_unlock();

See my comment above about rename and use of cpus_read_lock

Regards

Mike

> +
> +       /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */
> +       if (ret)
> +               return ret;
> +
> +       ret = amba_driver_register(&etm4x_driver);
> +       if (ret) {
> +               pr_info("Error registering etm4x driver\n");
> +               goto err_init;
> +       }
> +
> +       return ret;
> +
> +err_init:
> +       etm4_pm_clear();
> +       return ret;
> +}
> +module_init(etm4x_init);
> --
> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
> of Code Aurora Forum, hosted by The Linux Foundation
>
> _______________________________________________
> CoreSight mailing list
> CoreSight@lists.linaro.org
> https://lists.linaro.org/mailman/listinfo/coresight



-- 
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK

Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init

[Sai Prakash Ranjan]

Hi Mike,

On 2020-07-29 01:46, Mike Leach wrote:
> Hi Sai,
> 
> On Tue, 28 Jul 2020 at 08:51, Sai Prakash Ranjan
> <saiprakash.ranjan@codeaurora.org> wrote:
>> 
>> 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.
>> 
>> 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>
>> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
>> ---
>> 
>> Changes in v2:
>>  * Rearrange cpuhp callbacks and move them to driver init (Suzuki K 
>> Poulose)
>> 
>> ---
>>  drivers/hwtracing/coresight/coresight-etm4x.c | 51 
>> ++++++++++---------
>>  1 file changed, 27 insertions(+), 24 deletions(-)
>> 
>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c 
>> b/drivers/hwtracing/coresight/coresight-etm4x.c
>> index 6d7d2169bfb2..adb71987a1e3 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,
>> @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(void)
>>  {
> 
> consider renaming this to etm4_pm_setup() and handing any cpu locking
> inside the function.
> In the circumstances - as part of the driver init rather than probe it
> may be sufficient to call the cpuhp_setup functions without the
> _cpuslocked suffix and allow the calls to lock the cpus as they are
> made.
> i.e. cpuhp_setup_state_nocalls_cpuslocked() => 
> cpuhp_setup_state_nocalls()

Sure, will make this change.

> 
>>         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",
>> @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void)
>> 
>>  unregister_notifier:
>>         cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
>> -
>> -reduce_count:
>> -       --etm4_count;
>>         return ret;
>>  }
>> 
>>  static void 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) {
>> @@ -1498,22 +1487,12 @@ 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;
>> @@ -1560,7 +1539,6 @@ 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;
>>  }
>> 
>> @@ -1598,4 +1576,29 @@ 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;
>> +
>> +       cpus_read_lock();
>> +       ret = etm4_pm_setup_cpuslocked();
>> +       cpus_read_unlock();
> 
> See my comment above about rename and use of cpus_read_lock
> 

Yes, thanks for the review Mike.

Thanks,
Sai

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