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>

drivers/cpufreq/cpufreq.c

@@ -1739,17 +1739,8 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
 			pr_err("%s: Failed to change cpu frequency: %d\n",
 					__func__, retval);
 
-		if (notify) {
-			/*
-			 * Notify with old freq in case we failed to change
-			 * frequency
-			 */
-			if (retval)
-				freqs.new = freqs.old;
-
-			cpufreq_notify_transition(policy, &freqs,
-					CPUFREQ_POSTCHANGE);
-		}
+		if (notify)
+			cpufreq_notify_post_transition(policy, &freqs, retval);
 	}
 
 out:

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)

drivers/cpufreq/powernow-k8.c

@@ -964,14 +964,9 @@ static int transition_frequency_fidvid(struct powernow_k8_data *data,
 	cpufreq_cpu_put(policy);
 
 	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
-
 	res = transition_fid_vid(data, fid, vid);
-	if (res)
-		freqs.new = freqs.old;
-	else
-		freqs.new = find_khz_freq_from_fid(data->currfid);
+	cpufreq_notify_post_transition(policy, &freqs, res);
 
-	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
 	return res;
 }
 

drivers/cpufreq/unicore2-cpufreq.c

@@ -46,20 +46,18 @@ static int ucv2_target(struct cpufreq_policy *policy,
 			 unsigned int target_freq,
 			 unsigned int relation)
 {
-	unsigned int cur = ucv2_getspeed(0);
 	struct cpufreq_freqs freqs;
 	struct clk *mclk = clk_get(NULL, "MAIN_CLK");
+	int ret;
 
-	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
-
-	if (!clk_set_rate(mclk, target_freq * 1000)) {
-		freqs.old = cur;
+	freqs.old = policy->cur;
 	freqs.new = target_freq;
-	}
 
-	cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
+	cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
+	ret = clk_set_rate(mclk, target_freq * 1000);
+	cpufreq_notify_post_transition(policy, &freqs, ret);
 
-	return 0;
+	return ret;
 }
 
 static int __init ucv2_cpu_init(struct cpufreq_policy *policy)