cpufreq: arm_big_little: fix frequency check when bL switcher is active

The check for correct frequency being set in bL_cpufreq_set_rate is
broken when the big.LITTLE switcher is active, for two reasons.

 1. The 'new_rate' variable gets overwritten before the test by the
 code calculating the frequency of the old cluster.

 2. The frequency returned by bL_cpufreq_get_rate will be the virtual
 frequency, not the actual one the intended version of new_rate contains.

This means the function always returns an error causing an endless
stream of: "cpufreq: __target_index: Failed to change cpu frequency: -5"

As the intent is to check for errors that clk_set_rate doesn't report
lets move the check to immediately after that and directly use
clk_get_rate, rather than the arm_big_little helpers which only confuse
matters. Also, update the comment to be hopefully clearer about the
purpose of the code.

Fixes: 0a95e630b49a (cpufreq: arm_big_little: check if the frequency is set correctly)
Signed-off-by: Jon Medhurst <tixy@linaro.org>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Reviewed-by: Michael Turquette <mturquette@baylibre.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c
index f1e42f8ce0fcc75a5e67ae4e5365d098d83cfc32..c5d256caa664a63731e0cb7db6f5b00e31c750d8 100644 (file)
--- a/drivers/cpufreq/arm_big_little.c
+++ b/drivers/cpufreq/arm_big_little.c
@@ -149,6 +149,19 @@ 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 hasn't returned an error here however it
+                * may be that clk_change_rate failed due to hardware or
+                * firmware issues and wasn't able to report that due to the
+                * current design of the clk core layer. To work around this
+                * problem we will read back the clock rate and check it is
+                * correct. 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 +202,6 @@ 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;
 }