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patch "coresight: etmv4: Fix CPU power management setup in probe() function" added to char-misc-linus

PATCH [email protected] 1 participant 1 message Jul 1, 2020

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This is a note to let you know that I've just added the patch titled

coresight: etmv4: Fix CPU power management setup in probe() function

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 9b6a3f3633a5cc928b78627764793b60cb62e0f6 Mon Sep 17 00:00:00 2001
From: Mike Leach <[email protected]>
Date: Wed, 1 Jul 2020 10:08:52 -0600
Subject: coresight: etmv4: Fix CPU power management setup in probe() function

The current probe() function calls a pair of cpuhp_xxx API functions to setup CPU hotplug handling. The hotplug lock is held for the duration of the two calls and other CPU related code using cpus_read_lock() / cpus_read_unlock() calls.

The problem is that on error states, goto: statements bypass the cpus_read_unlock() call. This code has increased in complexity as the driver has developed.

This patch introduces a pair of helper functions etm4_pm_setup_cpuslocked() and etm4_pm_clear() which correct the issues above and group the PM code a little better.

The two functions etm4_cpu_pm_register() and etm4_cpu_pm_unregister() are dropped as these call cpu_pm_register_notifier() / ..unregister_notifier() dependent on CONFIG_CPU_PM - but this define is used to nop these functions out in the pm headers - so the wrapper functions are superfluous.

Fixes f188b5e76aae ("coresight: etm4x: Save/restore state across CPU low power states")
Fixes e9f5d63f84fe ("hwtracing/coresight-etm4x: Use cpuhp_setup_state_nocalls_cpuslocked()")
Fixes 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state machine")
Signed-off-by Mike Leach <[email protected]>
Cc stable <[email protected]>
Reviewed-by Mathieu Poirier <[email protected]>
Link https://lore.kernel.org/r/[email protected] open here
Signed-off-by Greg Kroah-Hartman <[email protected]>
---
 drivers/hwtracing/coresight/coresight-etm4x.c | 82 ++++++++++++-------
 1 file changed, 53 insertions(+), 29 deletions(-)
drivers/hwtracing/coresight/coresight-etm4x.c +53 -29
index 747afc875f91..0c35cd5e0d1d 100644
@@ -1388,18 +1388,57 @@ static struct notifier_block etm4_cpu_pm_nb = {
 	.notifier_call = etm4_cpu_pm_notify,
 };
 
-static int etm4_cpu_pm_register(void)
+/* Setup PM. Called with cpus locked. Deals with error conditions and counts */
+static int etm4_pm_setup_cpuslocked(void)
 {
-	if (IS_ENABLED(CONFIG_CPU_PM))
-		return cpu_pm_register_notifier(&etm4_cpu_pm_nb);
+	int ret;
 
-	return 0;
+	if (etm4_count++)
+		return 0;
+
+	ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb);
+	if (ret)
+		goto reduce_count;
+
+	ret = cpuhp_setup_state_nocalls_cpuslocked(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);
+
+	/* HP dyn state ID returned in ret on success */
+	if (ret > 0) {
+		hp_online = ret;
+		return 0;
+	}
+
+	/* failed dyn state - remove others */
+	cpuhp_remove_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING);
+
+unregister_notifier:
+	cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
+
+reduce_count:
+	--etm4_count;
+	return ret;
 }
 
-static void etm4_cpu_pm_unregister(void)
+static void etm4_pm_clear(void)
 {
-	if (IS_ENABLED(CONFIG_CPU_PM))
-		cpu_pm_unregister_notifier(&etm4_cpu_pm_nb);
+	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) {
+		cpuhp_remove_state_nocalls(hp_online);
+		hp_online = 0;
+	}
 }
 
 static int etm4_probe(struct amba_device *adev, const struct amba_id *id)

@@ -1453,24 +1492,15 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 				etm4_init_arch_data,  drvdata, 1))
 		dev_err(dev, "ETM arch init failed\n");
 
-	if (!etm4_count++) {
-		cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING,
-						     "arm/coresight4:starting",
-						     etm4_starting_cpu, etm4_dying_cpu);
-		ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN,
-							   "arm/coresight4:online",
-							   etm4_online_cpu, NULL);
-		if (ret < 0)
-			goto err_arch_supported;
-		hp_online = ret;
+	ret = etm4_pm_setup_cpuslocked();
+	cpus_read_unlock();
 
-		ret = etm4_cpu_pm_register();
-		if (ret)
-			goto err_arch_supported;
+	/* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */
+	if (ret) {
+		etmdrvdata[drvdata->cpu] = NULL;
+		return ret;
 	}
 
-	cpus_read_unlock();
-
 	if (etm4_arch_supported(drvdata->arch) == false) {
 		ret = -EINVAL;
 		goto err_arch_supported;

@@ -1517,13 +1547,7 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id)
 
 err_arch_supported:
 	etmdrvdata[drvdata->cpu] = NULL;
-	if (--etm4_count == 0) {
-		etm4_cpu_pm_unregister();
-
-		cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
-		if (hp_online)
-			cpuhp_remove_state_nocalls(hp_online);
-	}
+	etm4_pm_clear();
 	return ret;
 }
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