@@ -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)
In the current code, if we fail during a frequency transition we simply send the POSTCHANGE notification with old frequency. This isn't enough. One of the core user of these notifications is the code responsible for keeping loops_per_jiffy aligned with frequency change. 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 correct order. Also it fills freqs.old before starting the first notification, this was missing since ever. Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> --- drivers/cpufreq/pcc-cpufreq.c | 18 +++++++----------- 1 file changed, 7 insertions(+), 11 deletions(-)