Re: [PATCH] cpufreq: arm_big_little: fix frequency check when bL switcher is active

[Sudeep Holla]

On 13/10/15 08:19, Jon Medhurst (Tixy) wrote:
> On Mon, 2015-10-12 at 14:20 +0100, Sudeep Holla wrote:
> > On 08/10/15 10:23, Jon Medhurst (Tixy) wrote:
> > [...]
> >
> > > diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c
> > > index f1e42f8..59115a4 100644
> > > --- a/drivers/cpufreq/arm_big_little.c
> > > +++ b/drivers/cpufreq/arm_big_little.c
> > > @@ -149,6 +149,18 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32 new_cluster, u32 rate)
> > >    			__func__, cpu, old_cluster, new_cluster, new_rate);
> > >
> > >    	ret = clk_set_rate(clk[new_cluster], new_rate * 1000);
> > > +	if (!ret) {
> > > +		/*
> > > +		 * FIXME: clk_set_rate has to handle the case where clk_change_rate
> > > +		 * can fail due to hardware or firmware issues. Until the clk core
> > > +		 * layer is fixed, we can check here. In most of the cases we will
> > > +		 * be reading only the cached value anyway. This needs to  be removed
> > > +		 * once clk core is fixed.
> > > +		 */
> > > +		if (clk_get_rate(clk[new_cluster]) != new_rate * 1000)
> > > +			ret = -EIO;
> > > +	}
> > > +
> > >    	if (WARN_ON(ret)) {
> > >    		pr_err("clk_set_rate failed: %d, new cluster: %d\n", ret,
> > >    				new_cluster);
> > > @@ -189,15 +201,6 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32 new_cluster, u32 rate)
> > >    		mutex_unlock(&cluster_lock[old_cluster]);
> > >    	}
> > >
> > > -	/*
> > > -	 * FIXME: clk_set_rate has to handle the case where clk_change_rate
> > > -	 * can fail due to hardware or firmware issues. Until the clk core
> > > -	 * layer is fixed, we can check here. In most of the cases we will
> > > -	 * be reading only the cached value anyway. This needs to  be removed
> > > -	 * once clk core is fixed.
> > > -	 */
> > > -	if (bL_cpufreq_get_rate(cpu) != new_rate)
> > > -		return -EIO;
> > >    	return 0;
> > >    }
> >
> > The above change looks good to me but with minor nit. You can get rid of
> > if(!ret) check if you move the hunk after if (WARN_ON(ret))
>
> But then we wouldn't get the WARN_ON and pr_err triggered when we detect
> the clock rate isn't set, which surely is half the reason for the check
> in the first place?

Not sure if I understand what you mean or may be I was not clear, so
thought I will put the delta here. Let me know if and how its still a 
problem.

Regards,
Sudeep

-->8

diff --git i/drivers/cpufreq/arm_big_little.c 
w/drivers/cpufreq/arm_big_little.c
index f1e42f8ce0fc..05e850f80f39 100644
--- i/drivers/cpufreq/arm_big_little.c
+++ w/drivers/cpufreq/arm_big_little.c
@@ -164,6 +164,16 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32 
new_cluster, u32 rate)

        mutex_unlock(&cluster_lock[new_cluster]);

+       /*
+        * FIXME: clk_set_rate has to handle the case where clk_change_rate
+        * can fail due to hardware or firmware issues. Until the clk core
+        * layer is fixed, we can check here. In most of the cases we will
+        * be reading only the cached value anyway. This needs to  be 
removed
+        * once clk core is fixed.
+        */
+       if (bL_cpufreq_get_rate(cpu) != new_rate)
+               return -EIO;
+
        /* Recalc freq for old cluster when switching clusters */
        if (old_cluster != new_cluster) {
                pr_debug("%s: cpu: %d, old cluster: %d, new cluster: %d\n",
@@ -189,15 +199,6 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32 
new_cluster, u32 rate)
                mutex_unlock(&cluster_lock[old_cluster]);
        }

-       /*
-        * FIXME: clk_set_rate has to handle the case where clk_change_rate
-        * can fail due to hardware or firmware issues. Until the clk core
-        * layer is fixed, we can check here. In most of the cases we will
-        * be reading only the cached value anyway. This needs to  be 
removed
-        * once clk core is fixed.
-        */
-       if (bL_cpufreq_get_rate(cpu) != new_rate)
-               return -EIO;
        return 0;
 }
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