soc: qcom: add API for matching voltages across CPUs

Create an API to match voltages across asymmetric CPUs as
this can be useful in systems with a shared rail across CPUs.
The API takes in one input argument which is the frequency of
a big cluster CPU for which a voltage-equivalent little cluster
CPU frequency is desired. The return value is this little
cluster CPU frequency. All frequencies are in units of kHz.

Change-Id: I821819a0761566984dd7f92014599ff0fcb85e90
Signed-off-by: Amir Vajid <avajid@codeaurora.org>

drivers/soc/qcom/Makefile

@@ -38,6 +38,7 @@ obj-$(CONFIG_MSM_PIL_MSS_QDSP6V5) += pil-q6v5.o pil-msa.o pil-q6v5-mss.o
 obj-$(CONFIG_MSM_PIL)   +=      peripheral-loader.o
 obj-$(CONFIG_MSM_CORE_CTL_HELPER) += core_ctl_helper.o
 obj-$(CONFIG_MSM_PFE_WA) += pfe-wa.o
+obj-$(CONFIG_ARCH_MSM8996) += msm_cpu_voltage.o
 
 ifdef CONFIG_MSM_SUBSYSTEM_RESTART
 	obj-y += subsystem_notif.o

drivers/soc/qcom/msm_cpu_voltage.c

@@ -0,0 +1,140 @@
+/*
+ * Copyright (c) 2016, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/cpu.h>
+#include <linux/pm_opp.h>
+#include <linux/kernel.h>
+#include <soc/qcom/msm_cpu_voltage.h>
+
+#define MAX_FREQ_GAP_KHZ 200000
+
+static unsigned int cls0_max_freq;
+
+static unsigned int get_max_freq(struct device *dev)
+{
+	struct dev_pm_opp *opp = NULL;
+	unsigned long freq = ULONG_MAX;
+
+	if (!dev)
+		return 0;
+
+	opp = dev_pm_opp_find_freq_floor(dev, &freq);
+	if (IS_ERR(opp))
+		return 0;
+
+	freq /= 1000;
+
+	return freq;
+}
+
+/**
+  * msm_match_cpu_voltage_btol(): match voltage from a big to little cpu
+  *
+  * @input_freq - big cluster frequency (in kHz)
+  *
+  * Returns voltage equivalent little cluster frequency (in kHz)
+  * or 0 on any error.
+  *
+  * Function to get a voltage equivalent little cluster frequency
+  * for a particular big cluster frequency. Note that input_freq will
+  * be rounded up to nearest big cluster frequency. Returned frequency
+  * has some restrictions (e.g. can't be more than MAX_FREQ_GAP_KHZ
+  * kHz less than input_freq).
+  */
+unsigned int msm_match_cpu_voltage_btol(unsigned int input_freq)
+{
+	struct dev_pm_opp *opp = NULL;
+	struct device *cls0_dev = NULL;
+	struct device *cls1_dev = NULL;
+	unsigned long freq = 0;
+	unsigned long input_volt = 0;
+	unsigned int input_freq_actual = 0;
+	unsigned int target_freq = 0;
+	unsigned int temp_freq = 0;
+	unsigned long temp_volt = 0;
+	int i, max_opps_cls0 = 0;
+
+	cls0_dev = get_cpu_device(0);
+	if (!cls0_dev) {
+		pr_err("Error getting CPU0 device\n");
+		return 0;
+	}
+	cls1_dev = get_cpu_device(2);
+	if (!cls1_dev) {
+		pr_err("Error getting CPU2 device\n");
+		return 0;
+	}
+
+	if (cls0_max_freq == 0)
+		cls0_max_freq = get_max_freq(cls0_dev);
+
+	/*
+	 * Parse Cluster 1 OPP table for closest freq to input_freq
+	 * and save its voltage
+	 */
+	freq = input_freq * 1000;
+	rcu_read_lock();
+	opp = dev_pm_opp_find_freq_ceil(cls1_dev, &freq);
+	if (IS_ERR(opp)) {
+		pr_err("Error: could not find freq close to input_freq: %u\n",
+				input_freq);
+		goto exit;
+	}
+	input_freq_actual = freq / 1000;
+	input_volt = dev_pm_opp_get_voltage(opp);
+	if (input_volt == 0) {
+		pr_err("Error getting OPP voltage on cluster 1\n");
+		goto exit;
+	}
+
+	/*
+	 * Parse Cluster 0 OPP table for closest voltage to input_volt
+	 * and iterate to end to save max freq of Cluster 0
+	 */
+	max_opps_cls0 = dev_pm_opp_get_opp_count(cls0_dev);
+	if (max_opps_cls0 <= 0)
+		pr_err("Error getting OPP count for CPU0\n");
+	for (i = 0, freq = 0; i < max_opps_cls0; i++, freq++) {
+		opp = dev_pm_opp_find_freq_ceil(cls0_dev, &freq);
+		if (IS_ERR(opp)) {
+			pr_err("Error getting OPP freq on cluster 0\n");
+			goto exit;
+		}
+		temp_freq = freq / 1000;
+		temp_volt = dev_pm_opp_get_voltage(opp);
+		if (temp_volt >= input_volt) {
+			/* Continue to next frequency if gap is too large */
+			if ((temp_freq + MAX_FREQ_GAP_KHZ) < input_freq_actual)
+				continue;
+			/* block freq higher than input_freq */
+			if (temp_freq > input_freq)
+				target_freq = input_freq;
+			else
+				target_freq = temp_freq;
+			break;
+		}
+	}
+
+	/*
+	 * If we didn't find a frequency, either input voltage is too high
+	 * or gap was too large (input frequency was too high). In either
+	 * case, return Cluster 0 Fmax as this is the best possible freq.
+	 * Also, if input_freq is > Cluster 0 Fmax, return Cluster 0 Fmax.
+	 */
+	if (target_freq == 0 || input_freq > cls0_max_freq)
+		target_freq = cls0_max_freq;
+exit:
+	rcu_read_unlock();
+	return target_freq;
+}
+EXPORT_SYMBOL(msm_match_cpu_voltage_btol);

include/soc/qcom/msm_cpu_voltage.h

@@ -0,0 +1,14 @@
+/*
+ * Copyright (c) 2016, The Linux Foundation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+unsigned int msm_match_cpu_voltage_btol(unsigned int input_freq);