[PATCH 2/3] iio: adc: stm32-adc: add analog switches supply control

[Fabrice Gasnier]

On stm32h7 and stm32mp1, the ADC inputs are multiplexed with analog
switches which have reduced performances when their supply is below 2.7V
(vdda by default):
- vdd supply can be selected if above 2.7V by setting ANASWVDD syscfg bit
  (STM32MP1 only).
- Voltage booster can be used, to get full ADC performances by setting
  BOOSTE/EN_BOOSTER syscfg bit (increases power consumption).

Make this optional, since this is a trade-off between analog performance
and power consumption.

Note: STM32H7 syscfg has a set and clear register for "BOOSTE" control.
STM32MP1 has separate set and clear registers pair to control EN_BOOSTER
and ANASWVDD bits.

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
---
 drivers/iio/adc/stm32-adc-core.c | 232 ++++++++++++++++++++++++++++++++++++++-
 1 file changed, 230 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
index 2327ec1..9d41b16 100644
--- a/drivers/iio/adc/stm32-adc-core.c
+++ b/drivers/iio/adc/stm32-adc-core.c
@@ -14,9 +14,11 @@
 #include <linux/irqchip/chained_irq.h>
 #include <linux/irqdesc.h>
 #include <linux/irqdomain.h>
+#include <linux/mfd/syscon.h>
 #include <linux/module.h>
 #include <linux/of_device.h>
 #include <linux/pm_runtime.h>
+#include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/slab.h>
 
@@ -51,6 +53,20 @@
 
 #define STM32_ADC_CORE_SLEEP_DELAY_MS	2000
 
+/* SYSCFG registers */
+#define STM32H7_SYSCFG_PMCR		0x04
+#define STM32MP1_SYSCFG_PMCSETR		0x04
+#define STM32MP1_SYSCFG_PMCCLRR		0x44
+
+/* SYSCFG bit fields */
+#define STM32H7_SYSCFG_BOOSTE_MASK	BIT(8)
+#define STM32MP1_SYSCFG_ANASWVDD_MASK	BIT(9)
+
+/* SYSCFG capability flags */
+#define HAS_VBOOSTER		BIT(0)
+#define HAS_ANASWVDD		BIT(1)
+#define HAS_CLEAR_REG		BIT(2)
+
 /**
  * stm32_adc_common_regs - stm32 common registers, compatible dependent data
  * @csr:	common status register offset
@@ -58,6 +74,11 @@
  * @eoc1:	adc1 end of conversion flag in @csr
  * @eoc2:	adc2 end of conversion flag in @csr
  * @eoc3:	adc3 end of conversion flag in @csr
+ * @has_syscfg: SYSCFG capability flags
+ * @pmcr:	SYSCFG_PMCSETR/SYSCFG_PMCR register offset
+ * @pmcc:	SYSCFG_PMCCLRR clear register offset
+ * @booste_msk:	SYSCFG BOOSTE / EN_BOOSTER bitmask in PMCR & PMCCLRR
+ * @anaswvdd_msk: SYSCFG ANASWVDD bitmask in PMCR & PMCCLRR
  */
 struct stm32_adc_common_regs {
 	u32 csr;
@@ -65,6 +86,11 @@ struct stm32_adc_common_regs {
 	u32 eoc1_msk;
 	u32 eoc2_msk;
 	u32 eoc3_msk;
+	unsigned int has_syscfg;
+	u32 pmcr;
+	u32 pmcc;
+	u32 booste_msk;
+	u32 anaswvdd_msk;
 };
 
 struct stm32_adc_priv;
@@ -87,20 +113,26 @@ struct stm32_adc_priv_cfg {
  * @domain:		irq domain reference
  * @aclk:		clock reference for the analog circuitry
  * @bclk:		bus clock common for all ADCs, depends on part used
+ * @vdd:		vdd supply reference
+ * @vdda:		vdda supply reference
  * @vref:		regulator reference
  * @cfg:		compatible configuration data
  * @common:		common data for all ADC instances
  * @ccr_bak:		backup CCR in low power mode
+ * @syscfg:		reference to syscon, system control registers
  */
 struct stm32_adc_priv {
 	int				irq[STM32_ADC_MAX_ADCS];
 	struct irq_domain		*domain;
 	struct clk			*aclk;
 	struct clk			*bclk;
+	struct regulator		*vdd;
+	struct regulator		*vdda;
 	struct regulator		*vref;
 	const struct stm32_adc_priv_cfg	*cfg;
 	struct stm32_adc_common		common;
 	u32				ccr_bak;
+	struct regmap			*syscfg;
 };
 
 static struct stm32_adc_priv *to_stm32_adc_priv(struct stm32_adc_common *com)
@@ -284,6 +316,22 @@ static const struct stm32_adc_common_regs stm32h7_adc_common_regs = {
 	.ccr = STM32H7_ADC_CCR,
 	.eoc1_msk = STM32H7_EOC_MST,
 	.eoc2_msk = STM32H7_EOC_SLV,
+	.has_syscfg = HAS_VBOOSTER,
+	.pmcr = STM32H7_SYSCFG_PMCR,
+	.booste_msk = STM32H7_SYSCFG_BOOSTE_MASK,
+};
+
+/* STM32MP1 common registers definitions */
+static const struct stm32_adc_common_regs stm32mp1_adc_common_regs = {
+	.csr = STM32H7_ADC_CSR,
+	.ccr = STM32H7_ADC_CCR,
+	.eoc1_msk = STM32H7_EOC_MST,
+	.eoc2_msk = STM32H7_EOC_SLV,
+	.has_syscfg =  HAS_VBOOSTER | HAS_ANASWVDD | HAS_CLEAR_REG,
+	.pmcr = STM32MP1_SYSCFG_PMCSETR,
+	.pmcc = STM32MP1_SYSCFG_PMCCLRR,
+	.booste_msk = STM32H7_SYSCFG_BOOSTE_MASK,
+	.anaswvdd_msk = STM32MP1_SYSCFG_ANASWVDD_MASK,
 };
 
 /* ADC common interrupt for all instances */
@@ -388,16 +436,145 @@ static void stm32_adc_irq_remove(struct platform_device *pdev,
 	}
 }
 
+static int stm32_adc_core_switches_supply_en(struct device *dev)
+{
+	struct stm32_adc_common *common = dev_get_drvdata(dev);
+	struct stm32_adc_priv *priv = to_stm32_adc_priv(common);
+	const struct stm32_adc_common_regs *regs = priv->cfg->regs;
+	int ret, vdda, vdd = 0;
+	u32 mask, clrmask, setmask = 0;
+
+	/*
+	 * On STM32H7 and STM32MP1, the ADC inputs are multiplexed with analog
+	 * switches (via PCSEL) which have reduced performances when their
+	 * supply is below 2.7V (vdda by default):
+	 * - Voltage booster can be used, to get full ADC performances
+	 *   (increases power consumption).
+	 * - Vdd can be used to supply them, if above 2.7V (STM32MP1 only).
+	 *
+	 * This is optional, as this is a trade-off between analog performance
+	 * and power consumption.
+	 */
+	if (!regs->has_syscfg || !priv->vdda || !priv->syscfg) {
+		dev_dbg(dev, "Not configuring analog switches\n");
+		return 0;
+	}
+
+	ret = regulator_enable(priv->vdda);
+	if (ret < 0) {
+		dev_err(dev, "vdda enable failed %d\n", ret);
+		return ret;
+	}
+
+	ret = regulator_get_voltage(priv->vdda);
+	if (ret < 0) {
+		dev_err(dev, "vdda get voltage failed %d\n", ret);
+		goto vdda_dis;
+	}
+	vdda = ret;
+
+	if (priv->vdd && regs->has_syscfg & HAS_ANASWVDD) {
+		ret = regulator_enable(priv->vdd);
+		if (ret < 0) {
+			dev_err(dev, "vdd enable failed %d\n", ret);
+			goto vdda_dis;
+		}
+
+		ret = regulator_get_voltage(priv->vdd);
+		if (ret < 0) {
+			dev_err(dev, "vdd get voltage failed %d\n", ret);
+			goto vdd_dis;
+		}
+		vdd = ret;
+	}
+
+	/*
+	 * Recommended settings for ANASWVDD and EN_BOOSTER:
+	 * - vdda < 2.7V but vdd > 2.7V: ANASWVDD = 1, EN_BOOSTER = 0 (stm32mp1)
+	 * - vdda < 2.7V and vdd < 2.7V: ANASWVDD = 0, EN_BOOSTER = 1
+	 * - vdda >= 2.7V:               ANASWVDD = 0, EN_BOOSTER = 0 (default)
+	 */
+	if (vdda < 2700000) {
+		if (vdd > 2700000) {
+			dev_dbg(dev, "analog switches supplied by vdd\n");
+			setmask = regs->anaswvdd_msk;
+			clrmask = regs->booste_msk;
+		} else {
+			dev_dbg(dev, "Enabling voltage booster\n");
+			setmask = regs->booste_msk;
+			clrmask = regs->anaswvdd_msk;
+		}
+	} else {
+		dev_dbg(dev, "analog switches supplied by vdda\n");
+		clrmask = regs->booste_msk | regs->anaswvdd_msk;
+	}
+
+	mask = regs->booste_msk | regs->anaswvdd_msk;
+	if (regs->has_syscfg & HAS_CLEAR_REG) {
+		ret = regmap_write(priv->syscfg, regs->pmcc, clrmask);
+		if (ret) {
+			dev_err(dev, "syscfg clear failed, %d\n", ret);
+			goto vdd_dis;
+		}
+		mask = setmask;
+	}
+
+	ret = regmap_update_bits(priv->syscfg, regs->pmcr, mask, setmask);
+	if (ret) {
+		dev_err(dev, "syscfg update failed, %d\n", ret);
+		goto vdd_dis;
+	}
+
+	/* Booster voltage can take up to 50 us to stabilize */
+	if (setmask & regs->booste_msk)
+		usleep_range(50, 100);
+
+	return ret;
+
+vdd_dis:
+	if (priv->vdd && (regs->has_syscfg & HAS_ANASWVDD))
+		regulator_disable(priv->vdd);
+vdda_dis:
+	regulator_disable(priv->vdda);
+
+	return ret;
+}
+
+static void stm32_adc_core_switches_supply_dis(struct device *dev)
+{
+	struct stm32_adc_common *common = dev_get_drvdata(dev);
+	struct stm32_adc_priv *priv = to_stm32_adc_priv(common);
+	const struct stm32_adc_common_regs *regs = priv->cfg->regs;
+	u32 mask = regs->booste_msk | regs->anaswvdd_msk;
+
+	if (!regs->has_syscfg || !priv->vdda || !priv->syscfg)
+		return;
+
+	if (regs->has_syscfg & HAS_CLEAR_REG)
+		regmap_write(priv->syscfg, regs->pmcc, mask);
+	else
+		regmap_update_bits(priv->syscfg, regs->pmcr, mask, 0);
+
+	if (priv->vdd && (regs->has_syscfg & HAS_ANASWVDD))
+		regulator_disable(priv->vdd);
+
+	regulator_disable(priv->vdda);
+}
+
 static int stm32_adc_core_hw_start(struct device *dev)
 {
 	struct stm32_adc_common *common = dev_get_drvdata(dev);
 	struct stm32_adc_priv *priv = to_stm32_adc_priv(common);
 	int ret;
 
+	ret = stm32_adc_core_switches_supply_en(dev);
+	if (ret < 0)
+		return ret;
+
 	ret = regulator_enable(priv->vref);
 	if (ret < 0) {
 		dev_err(dev, "vref enable failed\n");
-		return ret;
+		goto err_switches_disable;
 	}
 
 	if (priv->bclk) {
@@ -425,6 +602,8 @@ static int stm32_adc_core_hw_start(struct device *dev)
 		clk_disable_unprepare(priv->bclk);
 err_regulator_disable:
 	regulator_disable(priv->vref);
+err_switches_disable:
+	stm32_adc_core_switches_supply_dis(dev);
 
 	return ret;
 }
@@ -441,6 +620,24 @@ static void stm32_adc_core_hw_stop(struct device *dev)
 	if (priv->bclk)
 		clk_disable_unprepare(priv->bclk);
 	regulator_disable(priv->vref);
+	stm32_adc_core_switches_supply_dis(dev);
+}
+
+static int stm32_adc_core_syscfg_probe(struct device_node *np,
+				       struct stm32_adc_priv *priv)
+{
+	if (!priv->cfg->regs->has_syscfg)
+		return 0;
+
+	priv->syscfg = syscon_regmap_lookup_by_phandle(np, "st,syscfg");
+	if (IS_ERR(priv->syscfg)) {
+		/* Optional */
+		if (PTR_ERR(priv->syscfg) != -ENODEV)
+			return PTR_ERR(priv->syscfg);
+		priv->syscfg = NULL;
+	}
+
+	return 0;
 }
 
 static int stm32_adc_probe(struct platform_device *pdev)
@@ -475,6 +672,30 @@ static int stm32_adc_probe(struct platform_device *pdev)
 		return ret;
 	}
 
+	priv->vdda = devm_regulator_get_optional(&pdev->dev, "vdda");
+	if (IS_ERR(priv->vdda)) {
+		ret = PTR_ERR(priv->vdda);
+		if (ret != -ENODEV) {
+			if (ret != -EPROBE_DEFER)
+				dev_err(&pdev->dev, "vdda get failed, %d\n",
+					ret);
+			return ret;
+		}
+		priv->vdda = NULL;
+	}
+
+	priv->vdd = devm_regulator_get_optional(&pdev->dev, "vdd");
+	if (IS_ERR(priv->vdd)) {
+		ret = PTR_ERR(priv->vdd);
+		if (ret != -ENODEV) {
+			if (ret != -EPROBE_DEFER)
+				dev_err(&pdev->dev, "vdd get failed, %d\n",
+					ret);
+			return ret;
+		}
+		priv->vdd = NULL;
+	}
+
 	priv->aclk = devm_clk_get(&pdev->dev, "adc");
 	if (IS_ERR(priv->aclk)) {
 		ret = PTR_ERR(priv->aclk);
@@ -495,6 +716,13 @@ static int stm32_adc_probe(struct platform_device *pdev)
 		priv->bclk = NULL;
 	}
 
+	ret = stm32_adc_core_syscfg_probe(np, priv);
+	if (ret) {
+		if (ret != -EPROBE_DEFER)
+			dev_err(&pdev->dev, "Can't probe syscfg: %d\n", ret);
+		return ret;
+	}
+
 	pm_runtime_get_noresume(dev);
 	pm_runtime_set_active(dev);
 	pm_runtime_set_autosuspend_delay(dev, STM32_ADC_CORE_SLEEP_DELAY_MS);
@@ -595,7 +823,7 @@ static const struct stm32_adc_priv_cfg stm32h7_adc_priv_cfg = {
 };
 
 static const struct stm32_adc_priv_cfg stm32mp1_adc_priv_cfg = {
-	.regs = &stm32h7_adc_common_regs,
+	.regs = &stm32mp1_adc_common_regs,
 	.clk_sel = stm32h7_adc_clk_sel,
 	.max_clk_rate_hz = 40000000,
 };
-- 
2.7.4