linux-kernel - Re: [PATCH V2] cpufreq: ARM big LITTLE: Add generic cpufreq driver and its DT glue

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Message-ID: <CAKohpo=zGZzE7Fvj6zhdwNcnLGX0LN0jbpo+1goJz586N20cXw@mail.gmail.com>
Date:	Mon, 15 Apr 2013 12:32:59 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Francesco Lavra <francescolavra.fl@...il.com>
Cc:	rjw@...k.pl, nicolas.pitre@...aro.org, robin.randhawa@....com,
	linux@....linux.org.uk, mark.hambleton@...adcom.com,
	linux-pm@...r.kernel.org,
	Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>,
	devicetree-discuss@...ts.ozlabs.org, Liviu.Dudau@....com,
	linux-kernel@...r.kernel.org, cpufreq@...r.kernel.org,
	linaro-kernel@...ts.linaro.org, Steve.Bannister@....com,
	arvind.chauhan@....com, linux-arm-kernel@...ts.infradead.org,
	charles.garcia-tobin@....com
Subject: Re: [PATCH V2] cpufreq: ARM big LITTLE: Add generic cpufreq driver
 and its DT glue

On 14 April 2013 01:43, Francesco Lavra <francescolavra.fl@...il.com> wrote:

>> +     for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
>
> If of_find_node_by_path() returns NULL, there will be a NULL pointer
> dereference.
>
>> +             if (count++ != cpu_dev->id)
>> +                     continue;
>> +             if (!of_get_property(np, "operating-points", NULL))
>> +                     return -ENODATA;
>> +
>> +             cpu_dev->of_node = np;
>> +
>> +             ret = of_init_opp_table(cpu_dev);
>> +             if (ret)
>> +                     return ret;
>> +
>> +             return 0;
>
> of_node_put() should be called on np before returning.
> Also, the reference count of the parent node should be decremented as well.
>
> These comments apply to the below function dt_get_transition_latency() too.

Thanks Francesco.

Below fixes this (I will send it separately to Rafael):

Subject: [PATCH 1/2] cpufreq: ARM big LITTLE: put DT nodes after using them

DT nodes should be put using of_node_put() to balance their usage counts. This
is not done properly in ARM's big LITTLE driver. Fix it.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 drivers/cpufreq/arm_big_little_dt.c | 43 +++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 14 deletions(-)

diff --git a/drivers/cpufreq/arm_big_little_dt.c
b/drivers/cpufreq/arm_big_little_dt.c
index 452ff46..44be311 100644
--- a/drivers/cpufreq/arm_big_little_dt.c
+++ b/drivers/cpufreq/arm_big_little_dt.c
@@ -31,22 +31,28 @@

 static int dt_init_opp_table(struct device *cpu_dev)
 {
-	struct device_node *np = NULL;
+	struct device_node *np, *parent;
 	int count = 0, ret;

-	for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
+	parent = of_find_node_by_path("/cpus");
+	if (!parent) {
+		pr_err("failed to find OF /cpus\n");
+		return -ENOENT;
+	}
+
+	for_each_child_of_node(parent, np) {
 		if (count++ != cpu_dev->id)
 			continue;
-		if (!of_get_property(np, "operating-points", NULL))
-			return -ENODATA;
-
-		cpu_dev->of_node = np;
-
-		ret = of_init_opp_table(cpu_dev);
-		if (ret)
-			return ret;
-
-		return 0;
+		if (!of_get_property(np, "operating-points", NULL)) {
+			ret = -ENODATA;
+		} else {
+			cpu_dev->of_node = np;
+			ret = of_init_opp_table(cpu_dev);
+		}
+		of_node_put(np);
+		of_node_put(parent);
+
+		return ret;
 	}

 	return -ENODEV;
@@ -54,15 +60,24 @@ static int dt_init_opp_table(struct device *cpu_dev)

 static int dt_get_transition_latency(struct device *cpu_dev)
 {
-	struct device_node *np = NULL;
+	struct device_node *np, *parent;
 	u32 transition_latency = CPUFREQ_ETERNAL;
 	int count = 0;

-	for_each_child_of_node(of_find_node_by_path("/cpus"), np) {
+	parent = of_find_node_by_path("/cpus");
+	if (!parent) {
+		pr_err("failed to find OF /cpus\n");
+		return -ENOENT;
+	}
+
+	for_each_child_of_node(parent, np) {
 		if (count++ != cpu_dev->id)
 			continue;

 		of_property_read_u32(np, "clock-latency", &transition_latency);
+		of_node_put(np);
+		of_node_put(parent);
+
 		return 0;
 	}
--
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