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

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Date:	Wed, 6 Mar 2013 00:38:36 +0800
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	rjw@...k.pl, Steve.Bannister@....com, linux-pm@...r.kernel.org,
	Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>,
	Liviu.Dudau@....com, linux-kernel@...r.kernel.org,
	cpufreq@...r.kernel.org, robin.randhawa@....com,
	linux-arm-kernel@...ts.infradead.org, mark.hambleton@...adcom.com,
	linaro-kernel@...ts.linaro.org, charles.garcia-tobin@....com
Subject: Re: [PATCH] cpufreq: ARM big LITTLE: Add generic cpufreq driver and
 its DT glue

On 5 March 2013 18:52, Russell King - ARM Linux <linux@....linux.org.uk> wrote:
> On Tue, Mar 05, 2013 at 12:52:41PM +0800, Viresh Kumar wrote:
>> +static void put_cluster_clk_and_freq_table(u32 cluster)
>> +{
>> +     if (!atomic_dec_return(&cluster_usage[cluster])) {
>> +             clk_put(clk[cluster]);
>> +             clk[cluster] = NULL;
>
> What's the point in setting the clk to NULL?

I couldn't find one and the same is true for freq_table[] too.

>> +static int get_cluster_clk_and_freq_table(u32 cluster)
>> +{
>> +     char name[9] = "cluster";
>> +     int count;
>> +
>> +     if (atomic_inc_return(&cluster_usage[cluster]) != 1)
>> +             return 0;
>> +
>> +     freq_table[cluster] = arm_bL_ops->get_freq_tbl(cluster, &count);
>> +     if (!freq_table[cluster])
>> +             goto atomic_dec;
>> +
>> +     name[7] = cluster + '0';
>> +     clk[cluster] = clk_get(NULL, name);
>> +     if (!IS_ERR_OR_NULL(clk[cluster])) {
>
> NAK.  Two reasons.
>
> 1. IS_ERR_OR_NULL.  You know about this, it's been on the list several
>    times.

AAHHHHHH .. How can i mess up with this concept.. I am really feeling bad now.

> 2. Maybe clk_get_sys() rather than clk_get() and use a sensible device
>    name ("cpu-cluster.%u" maybe) rather than a connection name with a
>    NULL device?

That's a good comment (rather than pointing at some stupid mistake), I will
probably keep the same name for the device as well.

So how does below fix look to you?

----------x-----------------x-----------------
diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c
index 0d6de0e..2486b9a 100644
--- a/drivers/cpufreq/arm_big_little.c
+++ b/drivers/cpufreq/arm_big_little.c
@@ -140,9 +140,7 @@ static void put_cluster_clk_and_freq_table(u32 cluster)
 {
        if (!atomic_dec_return(&cluster_usage[cluster])) {
                clk_put(clk[cluster]);
-               clk[cluster] = NULL;
                arm_bL_ops->put_freq_tbl(cluster);
-               freq_table[cluster] = NULL;
                pr_debug("%s: cluster: %d\n", __func__, cluster);
        }
 }
@@ -160,8 +158,8 @@ static int get_cluster_clk_and_freq_table(u32 cluster)
                goto atomic_dec;

        name[7] = cluster + '0';
-       clk[cluster] = clk_get(NULL, name);
-       if (!IS_ERR_OR_NULL(clk[cluster])) {
+       clk[cluster] = clk_get_sys(name, NULL);
+       if (!IS_ERR(clk[cluster])) {
                pr_debug("%s: clk: %p & freq table: %p, cluster: %d\n",
                                __func__, clk[cluster], freq_table[cluster],
                                cluster);
--
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