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

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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



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