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Date:	Thu, 20 Mar 2014 14:10:54 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:	lee.jones@...aro.org, kernel@...inux.com, broonie@...nel.org,
	devicetree@...r.kernel.org
Subject: [PATCH 1/1] regulator: Add new driver for ST's PWM controlled voltage regulators

On some STMicroelectronics hardware reside regulators consisting
partly of a PWM input connected to the feedback loop. As the PWM
duty-cycle is varied the output voltage adapts. This driver
allows us to vary the output voltage by adapting the PWM input
duty-cycle.

Signed-off-by: Lee Jones <lee.jones@...aro.org>
---
 drivers/regulator/Kconfig  |   6 ++
 drivers/regulator/Makefile |   1 +
 drivers/regulator/st-pwm.c | 195 +++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 202 insertions(+)
 create mode 100644 drivers/regulator/st-pwm.c

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index 6a79328..a6b29cb 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -432,6 +432,12 @@ config REGULATOR_S5M8767
 	 via I2C bus. S5M8767A have 9 Bucks and 28 LDOs output and
 	 supports DVS mode with 8bits of output voltage control.
 
+config REGULATOR_ST_PWM
+	tristate "STMicroelectronics PWM voltage regulator"
+	depends on ARCH_STI
+	help
+	 This driver supports ST's PWM controlled voltage regulators.
+
 config REGULATOR_TI_ABB
 	tristate "TI Adaptive Body Bias on-chip LDO"
 	depends on ARCH_OMAP
diff --git a/drivers/regulator/Makefile b/drivers/regulator/Makefile
index 979f9dd..d0c2bb8 100644
--- a/drivers/regulator/Makefile
+++ b/drivers/regulator/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_REGULATOR_PCF50633) += pcf50633-regulator.o
 obj-$(CONFIG_REGULATOR_RC5T583)  += rc5t583-regulator.o
 obj-$(CONFIG_REGULATOR_S2MPS11) += s2mps11.o
 obj-$(CONFIG_REGULATOR_S5M8767) += s5m8767.o
+obj-$(CONFIG_REGULATOR_ST_PWM) += st-pwm.o
 obj-$(CONFIG_REGULATOR_STW481X_VMMC) += stw481x-vmmc.o
 obj-$(CONFIG_REGULATOR_TI_ABB) += ti-abb-regulator.o
 obj-$(CONFIG_REGULATOR_TPS6105X) += tps6105x-regulator.o
diff --git a/drivers/regulator/st-pwm.c b/drivers/regulator/st-pwm.c
new file mode 100644
index 0000000..4630465
--- /dev/null
+++ b/drivers/regulator/st-pwm.c
@@ -0,0 +1,195 @@
+/*
+ * Regulator driver for ST's PWM Regulators
+ *
+ * Copyright (C) 2014 - STMicroelectronics Inc.
+ *
+ * Author: Lee Jones <lee.jones@...aro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/err.h>
+#include <linux/regulator/driver.h>
+#include <linux/regulator/machine.h>
+#include <linux/regulator/of_regulator.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/pwm.h>
+
+#define ST_PWM_REG_PERIOD 8448
+
+struct st_pwm_regulator_data {
+	struct pwm_device *pwm;
+	struct regulator_desc *desc;
+	struct st_pwm_voltages *duty_cycle_table;
+	bool enabled;
+	int state;
+};
+
+struct st_pwm_voltages {
+	unsigned int uV;
+	unsigned int dutycycle;
+};
+
+static int st_pwm_regulator_get_voltage(struct regulator_dev *dev)
+{
+	struct st_pwm_regulator_data *drvdata = rdev_get_drvdata(dev);
+
+	return drvdata->duty_cycle_table[drvdata->state].uV;
+}
+
+static int st_pwm_regulator_set_voltage(struct regulator_dev *dev,
+					int min_uV, int max_uV,
+					unsigned *selector)
+{
+	struct st_pwm_regulator_data *drvdata = rdev_get_drvdata(dev);
+	int dutycycle, best_val = INT_MAX;
+	int sel, ret;
+
+	for (sel = 0; sel < dev->desc->n_voltages; sel++) {
+		if (drvdata->duty_cycle_table[sel].uV < best_val &&
+		    drvdata->duty_cycle_table[sel].uV >= min_uV &&
+		    drvdata->duty_cycle_table[sel].uV <= max_uV) {
+			best_val = drvdata->duty_cycle_table[sel].uV;
+			if (selector)
+				*selector = sel;
+		}
+	}
+
+	if (best_val == INT_MAX)
+		return -EINVAL;
+
+	dutycycle = (ST_PWM_REG_PERIOD / 100) *
+		drvdata->duty_cycle_table[sel].dutycycle;
+
+	ret = pwm_config(drvdata->pwm, dutycycle, ST_PWM_REG_PERIOD);
+	if (ret) {
+		dev_err(&dev->dev, "Failed to configure PWM\n");
+		return ret;
+	}
+
+	drvdata->state = sel;
+
+	if (!drvdata->enabled) {
+		ret = pwm_enable(drvdata->pwm);
+		if (ret) {
+			dev_err(&dev->dev, "Failed to enable PWM\n");
+			return ret;
+		}
+		drvdata->enabled = true;
+	}
+
+	return 0;
+}
+
+static int st_pwm_regulator_list_voltage(struct regulator_dev *dev,
+					 unsigned selector)
+{
+	struct st_pwm_regulator_data *drvdata = rdev_get_drvdata(dev);
+
+	if (selector >= dev->desc->n_voltages)
+		return -EINVAL;
+
+	return drvdata->duty_cycle_table[selector].uV;
+}
+
+static struct regulator_ops st_pwm_regulator_voltage_ops = {
+	.get_voltage  = st_pwm_regulator_get_voltage,
+	.set_voltage  = st_pwm_regulator_set_voltage,
+	.list_voltage = st_pwm_regulator_list_voltage,
+};
+
+static struct st_pwm_voltages b2105_duty_cycle_table[] = {
+	{ .uV = 1114000, .dutycycle = 0,  },
+	{ .uV = 1095000, .dutycycle = 10, },
+	{ .uV = 1076000, .dutycycle = 20, },
+	{ .uV = 1056000, .dutycycle = 30, },
+	{ .uV = 1036000, .dutycycle = 40, },
+	{ .uV =  996000, .dutycycle = 50, },
+	/* WARNING: Values above 50% duty-cycle cause boot failures. */
+};
+
+static struct regulator_desc b2105_desc = {
+	.name		= "b2105-pwm-regulator",
+	.ops		= &st_pwm_regulator_voltage_ops,
+	.type		= REGULATOR_VOLTAGE,
+	.owner		= THIS_MODULE,
+	.n_voltages	= ARRAY_SIZE(b2105_duty_cycle_table),
+	.supply_name    = "pwm",
+};
+
+static struct st_pwm_regulator_data b2105_info = {
+	.desc		  = &b2105_desc,
+	.duty_cycle_table = b2105_duty_cycle_table,
+};
+
+static struct of_device_id st_pwm_of_match[] = {
+	{ .compatible = "st,b2105-pwm-regulator", .data = &b2105_info, },
+	{ },
+};
+
+static int st_pwm_regulator_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct st_pwm_regulator_data *drvdata;
+	const struct of_device_id *of_match;
+	struct regulator_dev *regulator;
+	struct regulator_config config = { };
+
+	if (!np) {
+		dev_err(&pdev->dev, "Device Tree node missing\n");
+		return -EINVAL;
+	}
+
+	of_match = of_match_device(st_pwm_of_match, &pdev->dev);
+	if (!of_match) {
+		dev_err(&pdev->dev, "failed to match of device\n");
+		return -ENODEV;
+	}
+	drvdata =  (struct st_pwm_regulator_data *) of_match->data;
+
+	config.init_data = of_get_regulator_init_data(&pdev->dev, np);
+	if (!config.init_data)
+		return -ENOMEM;
+
+	config.of_node = np;
+	config.dev = &pdev->dev;
+	config.driver_data = drvdata;
+
+	drvdata->pwm = devm_pwm_get(&pdev->dev, NULL);
+	if (IS_ERR(drvdata->pwm)) {
+		dev_err(&pdev->dev, "Failed to get PWM\n");
+		return PTR_ERR(drvdata->pwm);
+	}
+
+	regulator = devm_regulator_register(&pdev->dev, drvdata->desc, &config);
+	if (IS_ERR(regulator)) {
+		dev_err(&pdev->dev, "Failed to register regulator %s\n",
+			drvdata->desc->name);
+		return PTR_ERR(regulator);
+	}
+
+	dev_info(&pdev->dev, "ST PWM Regulator registered\n");
+
+	return 0;
+}
+
+static struct platform_driver st_pwm_regulator_driver = {
+	.driver = {
+		.name		= "st-pwm-regulator",
+		.owner		= THIS_MODULE,
+		.of_match_table = of_match_ptr(st_pwm_of_match),
+	},
+	.probe = st_pwm_regulator_probe,
+};
+
+module_platform_driver(st_pwm_regulator_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Lee Jones <lee.jones@...aro.org>");
+MODULE_DESCRIPTION("ST PWM Regulator Driver");
+MODULE_ALIAS("platform:st_pwm-regulator");
-- 
1.8.3.2

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