regulator: rk808: fixed the overshoot when adjust voltage

There is a overshoot in DCDC1/DCDC2, we have 2 method to workaround:
1st is use dvs pin to switch the voltage between value in BUCKn_ON_VSEL
and BUCKn_DVS_VSEL. If DVS pin is inactive, the voltage of DCDC1/DCDC2
are controlled by BUCKn_ON_VSEL, when we pull dvs1/dvs2 pin to active,
they would be controlled by BUCKn_DVS_VSEL. In this case, the ramp rate
is same as the value programmed in BUCKn_RATE, and the fastest rate is
10mv/us.
2nd method is gradual adjustment, adjust the voltage to a target value
step by step via i2c, each step is set to 100 mA. If you write the
voltage directly using an i2c write the rk808 will always ramp as fast
as it possibly can, about 100mv/us.

Signed-off-by: Chris Zhong <[e-mail]>
Reviewed-by: Doug Anderson <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/regulator/rk808-regulator.c

···
  * more details.
  */
 
-#include <linux/module.h>
+#include <linux/delay.h>
+#include <linux/gpio.h>
 #include <linux/i2c.h>
-#include <linux/mfd/rk808.h>
+#include <linux/module.h>
 #include <linux/of_device.h>
+#include <linux/of_gpio.h>
+#include <linux/mfd/rk808.h>
 #include <linux/regulator/driver.h>
 #include <linux/regulator/of_regulator.h>
 
···
 #define RK808_RAMP_RATE_6MV_PER_US	(2 << RK808_RAMP_RATE_OFFSET)
 #define RK808_RAMP_RATE_10MV_PER_US	(3 << RK808_RAMP_RATE_OFFSET)
 
+#define RK808_DVS2_POL		BIT(2)
+#define RK808_DVS1_POL		BIT(1)
+
 /* Offset from XXX_ON_VSEL to XXX_SLP_VSEL */
 #define RK808_SLP_REG_OFFSET 1
 
+/* Offset from XXX_ON_VSEL to XXX_DVS_VSEL */
+#define RK808_DVS_REG_OFFSET 2
+
 /* Offset from XXX_EN_REG to SLEEP_SET_OFF_XXX */
 #define RK808_SLP_SET_OFF_REG_OFFSET 2
+
+/* max steps for increase voltage of Buck1/2, equal 100mv*/
+#define MAX_STEPS_ONE_TIME 8
+
+struct rk808_regulator_data {
+	struct gpio_desc *dvs_gpio[2];
+};
 
 static const int rk808_buck_config_regs[] = {
 	RK808_BUCK1_CONFIG_REG,
···
 static const struct regulator_linear_range rk808_ldo6_voltage_ranges[] = {
 	REGULATOR_LINEAR_RANGE(800000, 0, 17, 100000),
 };
+
+static int rk808_buck1_2_get_voltage_sel_regmap(struct regulator_dev *rdev)
+{
+	struct rk808_regulator_data *pdata = rdev_get_drvdata(rdev);
+	int id = rdev->desc->id - RK808_ID_DCDC1;
+	struct gpio_desc *gpio = pdata->dvs_gpio[id];
+	unsigned int val;
+	int ret;
+
+	if (IS_ERR(gpio) || gpiod_get_value(gpio) == 0)
+		return regulator_get_voltage_sel_regmap(rdev);
+
+	ret = regmap_read(rdev->regmap,
+			  rdev->desc->vsel_reg + RK808_DVS_REG_OFFSET,
+			  &val);
+	if (ret != 0)
+		return ret;
+
+	val &= rdev->desc->vsel_mask;
+	val >>= ffs(rdev->desc->vsel_mask) - 1;
+
+	return val;
+}
+
+static int rk808_buck1_2_i2c_set_voltage_sel(struct regulator_dev *rdev,
+					     unsigned sel)
+{
+	int ret, delta_sel;
+	unsigned int old_sel, tmp, val, mask = rdev->desc->vsel_mask;
+
+	ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
+	if (ret != 0)
+		return ret;
+
+	tmp = val & ~mask;
+	old_sel = val & mask;
+	old_sel >>= ffs(mask) - 1;
+	delta_sel = sel - old_sel;
+
+	/*
+	 * If directly modify the register to change the voltage, we will face
+	 * the risk of overshoot. Put it into a multi-step, can effectively
+	 * avoid this problem, a step is 100mv here.
+	 */
+	while (delta_sel > MAX_STEPS_ONE_TIME) {
+		old_sel += MAX_STEPS_ONE_TIME;
+		val = old_sel << (ffs(mask) - 1);
+		val |= tmp;
+
+		/*
+		 * i2c is 400kHz (2.5us per bit) and we must transmit _at least_
+		 * 3 bytes (24 bits) plus start and stop so 26 bits.  So we've
+		 * got more than 65 us between each voltage change and thus
+		 * won't ramp faster than ~1500 uV / us.
+		 */
+		ret = regmap_write(rdev->regmap, rdev->desc->vsel_reg, val);
+		delta_sel = sel - old_sel;
+	}
+
+	sel <<= ffs(mask) - 1;
+	val = tmp | sel;
+	ret = regmap_write(rdev->regmap, rdev->desc->vsel_reg, val);
+
+	/*
+	 * When we change the voltage register directly, the ramp rate is about
+	 * 100000uv/us, wait 1us to make sure the target voltage to be stable,
+	 * so we needn't wait extra time after that.
+	 */
+	udelay(1);
+
+	return ret;
+}
+
+static int rk808_buck1_2_set_voltage_sel(struct regulator_dev *rdev,
+					 unsigned sel)
+{
+	struct rk808_regulator_data *pdata = rdev_get_drvdata(rdev);
+	int id = rdev->desc->id - RK808_ID_DCDC1;
+	struct gpio_desc *gpio = pdata->dvs_gpio[id];
+	unsigned int reg = rdev->desc->vsel_reg;
+	unsigned old_sel;
+	int ret, gpio_level;
+
+	if (IS_ERR(gpio))
+		return rk808_buck1_2_i2c_set_voltage_sel(rdev, sel);
+
+	gpio_level = gpiod_get_value(gpio);
+	if (gpio_level == 0) {
+		reg += RK808_DVS_REG_OFFSET;
+		ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &old_sel);
+	} else {
+		ret = regmap_read(rdev->regmap,
+				  reg + RK808_DVS_REG_OFFSET,
+				  &old_sel);
+	}
+
+	if (ret != 0)
+		return ret;
+
+	sel <<= ffs(rdev->desc->vsel_mask) - 1;
+	sel |= old_sel & ~rdev->desc->vsel_mask;
+
+	ret = regmap_write(rdev->regmap, reg, sel);
+	if (ret)
+		return ret;
+
+	gpiod_set_value(gpio, !gpio_level);
+
+	return ret;
+}
+
+static int rk808_buck1_2_set_voltage_time_sel(struct regulator_dev *rdev,
+				       unsigned int old_selector,
+				       unsigned int new_selector)
+{
+	struct rk808_regulator_data *pdata = rdev_get_drvdata(rdev);
+	int id = rdev->desc->id - RK808_ID_DCDC1;
+	struct gpio_desc *gpio = pdata->dvs_gpio[id];
+
+	/* if there is no dvs1/2 pin, we don't need wait extra time here. */
+	if (IS_ERR(gpio))
+		return 0;
+
+	return regulator_set_voltage_time_sel(rdev, old_selector, new_selector);
+}
 
 static int rk808_set_ramp_delay(struct regulator_dev *rdev, int ramp_delay)
 {
···
 static struct regulator_ops rk808_buck1_2_ops = {
 	.list_voltage		= regulator_list_voltage_linear_range,
 	.map_voltage		= regulator_map_voltage_linear_range,
-	.get_voltage_sel	= regulator_get_voltage_sel_regmap,
-	.set_voltage_sel	= regulator_set_voltage_sel_regmap,
+	.get_voltage_sel	= rk808_buck1_2_get_voltage_sel_regmap,
+	.set_voltage_sel	= rk808_buck1_2_set_voltage_sel,
+	.set_voltage_time_sel	= rk808_buck1_2_set_voltage_time_sel,
 	.enable			= regulator_enable_regmap,
 	.disable		= regulator_disable_regmap,
 	.is_enabled		= regulator_is_enabled_regmap,
···
 	[RK808_ID_SWITCH2]	= { .name = "SWITCH_REG2" },
 };
 
+static int rk808_regulator_dt_parse_pdata(struct device *dev,
+				   struct device *client_dev,
+				   struct regmap *map,
+				   struct rk808_regulator_data *pdata)
+{
+	struct device_node *np;
+	int tmp, ret, i;
+
+	np = of_get_child_by_name(client_dev->of_node, "regulators");
+	if (!np)
+		return -ENXIO;
+
+	ret = of_regulator_match(dev, np, rk808_reg_matches,
+				 RK808_NUM_REGULATORS);
+	if (ret < 0)
+		goto dt_parse_end;
+
+	for (i = 0; i < ARRAY_SIZE(pdata->dvs_gpio); i++) {
+		pdata->dvs_gpio[i] = gpiod_get_index(client_dev, "dvs", i);
+		if (IS_ERR(pdata->dvs_gpio[i])) {
+			dev_warn(dev, "there is no dvs%d gpio\n", i);
+			continue;
+		}
+
+		gpiod_direction_output(pdata->dvs_gpio[i], 0);
+
+		tmp = i ? RK808_DVS2_POL : RK808_DVS1_POL;
+		ret = regmap_update_bits(map, RK808_IO_POL_REG, tmp,
+				gpiod_is_active_low(pdata->dvs_gpio[i]) ?
+				0 : tmp);
+	}
+
+dt_parse_end:
+	of_node_put(np);
+	return ret;
+}
+
+static int rk808_regulator_remove(struct platform_device *pdev)
+{
+	struct rk808_regulator_data *pdata = platform_get_drvdata(pdev);
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(pdata->dvs_gpio); i++) {
+		if (!IS_ERR(pdata->dvs_gpio[i]))
+			gpiod_put(pdata->dvs_gpio[i]);
+	}
+
+	return 0;
+}
+
 static int rk808_regulator_probe(struct platform_device *pdev)
 {
 	struct rk808 *rk808 = dev_get_drvdata(pdev->dev.parent);
 	struct i2c_client *client = rk808->i2c;
-	struct device_node *reg_np;
 	struct regulator_config config = {};
 	struct regulator_dev *rk808_rdev;
+	struct rk808_regulator_data *pdata;
 	int ret, i;
 
-	reg_np = of_get_child_by_name(client->dev.of_node, "regulators");
-	if (!reg_np)
-		return -ENXIO;
+	pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL);
+	if (!pdata)
+		return -ENOMEM;
 
-	ret = of_regulator_match(&pdev->dev, reg_np, rk808_reg_matches,
-				 RK808_NUM_REGULATORS);
-	of_node_put(reg_np);
+	ret = rk808_regulator_dt_parse_pdata(&pdev->dev, &client->dev,
+					     rk808->regmap, pdata);
 	if (ret < 0)
 		return ret;
+
+	platform_set_drvdata(pdev, pdata);
 
 	/* Instantiate the regulators */
 	for (i = 0; i < RK808_NUM_REGULATORS; i++) {
···
 			continue;
 
 		config.dev = &client->dev;
-		config.driver_data = rk808;
+		config.driver_data = pdata;
 		config.regmap = rk808->regmap;
 		config.of_node = rk808_reg_matches[i].of_node;
 		config.init_data = rk808_reg_matches[i].init_data;
···
 
 static struct platform_driver rk808_regulator_driver = {
 	.probe = rk808_regulator_probe,
+	.remove = rk808_regulator_remove,
 	.driver = {
 		.name = "rk808-regulator",
+		.owner = THIS_MODULE,
 	},
 };