Re: [PATCH 1/6] cpufreq: cpufreq-cpu0: allow optional safe voltage during frequency transitions

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Hi Thomas,

Please see my comments inline.

On 09.01.2014 16:59, Thomas Abraham wrote:
[snip]
@@ -69,12 +71,26 @@ static int cpu0_set_target(struct cpufreq_policy *policy, unsigned int index)
  		 new_freq / 1000, volt ? volt / 1000 : -1);

  	/* scaling up?  scale voltage before frequency */
-	if (!IS_ERR(cpu_reg) && new_freq > old_freq) {
+	if (!IS_ERR(cpu_reg) && new_freq > old_freq &&
+				new_freq >= safe_frequency) {
  		ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
  		if (ret) {
  			pr_err("failed to scale voltage up: %d\n", ret);
  			return ret;
  		}
+	} else if (!IS_ERR(cpu_reg) && old_freq < safe_frequency) {
+		/*
+		 * the scaled up voltage level for the new_freq is lower
+		 * than the safe voltage level. so set safe_voltage
+		 * as the intermediate voltage level and revert it
+		 * back after the frequency has been changed.
+		 */
+		ret = regulator_set_voltage(cpu_reg, safe_voltage,
+						safe_voltage);

Shouldn't the tolerance be used here as well?

+		if (ret) {
+			pr_err("failed to set safe voltage: %d\n", ret);
+			return ret;
+		}
  	}

  	ret = clk_set_rate(cpu_clk, freq_exact);
@@ -94,6 +110,19 @@ static int cpu0_set_target(struct cpufreq_policy *policy, unsigned int index)
  		}
  	}

+	/*
+	 * if safe voltage was applied during voltage scale up, then set
+	 * the correct target voltage now.
+	 */
+	if (!IS_ERR(cpu_reg) && new_freq > old_freq &&
+					new_freq < safe_frequency) {
+		ret = regulator_set_voltage_tol(cpu_reg, volt, tol);
+		if (ret) {
+			pr_err("failed to scale voltage up: %d\n", ret);
+			return ret;
+		}
+	}
+

I believe that it would be enough to reuse the if block of scaling down instead of repeating the same code, just the condition must be slightly modified:

-	/* scaling down?  scale voltage after frequency */
-	if (!IS_ERR(cpu_reg) && new_freq < old_freq) {
+	/*
+	 * scaling down or below safe frequency?
+	 * scale voltage after frequency
+	 */
+	if (!IS_ERR(cpu_reg)
+	    && (new_freq < old_freq || new_freq < safe_frequency)) {

Best regards,
Tomasz
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