cpufreq: send new set of notification for transition failures

In the current code, if we fail during a frequency transition, we
simply send the POSTCHANGE notification with the old frequency. This
isn't enough.

One of the core users of these notifications is the code responsible
for keeping loops_per_jiffy aligned with frequency changes. And mostly
it is written as:

	if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
	    (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
		update-loops-per-jiffy...
	}

So, suppose we are changing to a higher frequency and failed during
transition, then following will happen:
- CPUFREQ_PRECHANGE notification with freq-new > freq-old
- CPUFREQ_POSTCHANGE notification with freq-new == freq-old

The first one will update loops_per_jiffy and second one will do
nothing. Even if we send the 2nd notification by exchanging values of
freq-new and old, some users of these notifications might get
unstable.

This can be fixed by simply calling cpufreq_notify_post_transition()
with error code and this routine will take care of sending
notifications in the correct order.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
[rjw: Folded 3 patches into one, rebased unicore2 changes]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 7 insertions, 11 deletions

diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c
index e2b4f40ff69a..1c0f1067af73 100644
--- a/drivers/cpufreq/pcc-cpufreq.c
+++ b/drivers/cpufreq/pcc-cpufreq.c
@@ -213,6 +213,7 @@ static int pcc_cpufreq_target(struct cpufreq_policy *policy,
 		cpu, target_freq,
 		(pcch_virt_addr + pcc_cpu_data->input_offset));
 
+	freqs.old = policy->cur;
 	freqs.new = target_freq;
 	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
 
@@ -228,25 +229,20 @@ static int pcc_cpufreq_target(struct cpufreq_policy *policy,
 	memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);
 
 	status = ioread16(&pcch_hdr->status);
+	iowrite16(0, &pcch_hdr->status);
+
+	cpufreq_notify_post_transition(policy, &freqs, status != CMD_COMPLETE);
+	spin_unlock(&pcc_lock);
+
 	if (status != CMD_COMPLETE) {
 		pr_debug("target: FAILED for cpu %d, with status: 0x%x\n",
 			cpu, status);
-		goto cmd_incomplete;
+		return -EINVAL;
 	}
-	iowrite16(0, &pcch_hdr->status);
 
-	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
 	pr_debug("target: was SUCCESSFUL for cpu %d\n", cpu);
-	spin_unlock(&pcc_lock);
 
 	return 0;
-
-cmd_incomplete:
-	freqs.new = freqs.old;
-	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
-	iowrite16(0, &pcch_hdr->status);
-	spin_unlock(&pcc_lock);
-	return -EINVAL;
 }
 
 static int pcc_get_offset(int cpu)