[RFC PATCH 3/8] cpufreq: qcom-nvmem: provide vmin constraint for early Kraits

[Dmitry Baryshkov <dmitry.baryshkov@linaro.org>]

Early Krait CPUs required that core voltage was not below 1.15 V.
Implement this requirement by adding separate config_regulators
callback.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/cpufreq/qcom-cpufreq-nvmem.c | 67 +++++++++++++++++++++++++++-
 1 file changed, 66 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/qcom-cpufreq-nvmem.c b/drivers/cpufreq/qcom-cpufreq-nvmem.c
index 113f35668048..9312c8ab62a8 100644
--- a/drivers/cpufreq/qcom-cpufreq-nvmem.c
+++ b/drivers/cpufreq/qcom-cpufreq-nvmem.c
@@ -30,6 +30,8 @@
 #include <linux/slab.h>
 #include <linux/soc/qcom/smem.h>
 
+#include <asm/cputype.h>
+
 #include <dt-bindings/arm/qcom,ids.h>
 
 struct qcom_cpufreq_drv;
@@ -257,6 +259,66 @@ static const struct qcom_cpufreq_match_data match_data_apq8064 = {
 	.regulator_names = apq8064_regulator_names,
 };
 
+static const int krait_needs_vmin(void)
+{
+	switch (read_cpuid_id()) {
+	case 0x511F04D0: /* KR28M2A20 */
+	case 0x511F04D1: /* KR28M2A21 */
+	case 0x510F06F0: /* KR28M4A10 */
+		return 1;
+	default:
+		return 0;
+	};
+}
+
+#define KRAIT_VMIN	1150000
+#define KRAIT_VMIN_MAX	(KRAIT_VMIN + 25000)
+static int krait_config_regulator_vmin(struct device *dev,
+				       struct dev_pm_opp *old_opp, struct dev_pm_opp *new_opp,
+				       struct regulator **regulators, unsigned int count)
+{
+	struct regulator *reg = regulators[0];
+	struct dev_pm_opp_supply supply;
+	int ret;
+
+	/* This function only supports single regulator per device */
+	if (WARN_ON(count > 1)) {
+		dev_err(dev, "multiple regulators are not supported\n");
+		return -EINVAL;
+	}
+
+	if (IS_ERR(reg)) {
+		dev_dbg(dev, "%s: regulator not available: %ld\n", __func__,
+			PTR_ERR(reg));
+		return 0;
+	}
+
+	ret = dev_pm_opp_get_supplies(new_opp, &supply);
+	if (WARN_ON(ret))
+		return ret;
+
+	if (supply.u_volt_min < KRAIT_VMIN) {
+		supply.u_volt_min = KRAIT_VMIN;
+		supply.u_volt = KRAIT_VMIN;
+		supply.u_volt_max = KRAIT_VMIN_MAX;
+	}
+
+	dev_dbg(dev, "%s: voltages (mV): %lu %lu %lu\n", __func__,
+		supply.u_volt_min, supply.u_volt, supply.u_volt_max);
+
+	ret = regulator_set_voltage_triplet(reg,
+					    supply.u_volt_min,
+					    supply.u_volt,
+					    supply.u_volt_max);
+	if (ret)
+		dev_err(dev, "%s: failed to set voltage (%lu %lu %lu mV): %d\n",
+			__func__, supply.u_volt_min, supply.u_volt,
+			supply.u_volt_max, ret);
+
+	return ret;
+}
+
+
 static int qcom_cpufreq_probe(struct platform_device *pdev)
 {
 	struct qcom_cpufreq_drv *drv;
@@ -344,8 +406,11 @@ static int qcom_cpufreq_probe(struct platform_device *pdev)
 			config.virt_devs = NULL;
 		}
 
-		if (drv->data->regulator_names)
+		if (drv->data->regulator_names) {
 			config.regulator_names = drv->data->regulator_names;
+			if (krait_needs_vmin())
+				config.config_regulators = krait_config_regulator_vmin;
+		}
 
 		if (config.supported_hw ||
 		    config.genpd_names ||
-- 
2.39.2