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>
diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c
index e2b4f40..1c0f1067 100644
--- a/drivers/cpufreq/pcc-cpufreq.c
+++ b/drivers/cpufreq/pcc-cpufreq.c
@@ -213,6 +213,7 @@
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 @@
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)