4.2.8-ckt1 -stable review patch. If anyone has any objections, please let me know.
------------------
From: "Jon Medhurst \\(Tixy\\)" <tixy@xxxxxxxxxx>
commit 14f1ba3af6209f0394192ef07fe2bd9bccdc755f upstream.
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@xxxxxxxxxx>
Acked-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Reviewed-by: Michael Turquette <mturquette@xxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
---
drivers/cpufreq/arm_big_little.c | 22 +++++++++++++---------
1 file changed, 13 insertions(+), 9 deletions(-)
diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c
index f1e42f8..c5d256c 100644
--- 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;
}
--
1.9.1
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