adc: add Amlogic Meson SAR ADC driver

This patch adds the driver for the Amlogic Meson Successive Approximation
Register (SAR) A/D Converter based on the Linux IIO driver thanks to the
great work of Martin Blumenstingl.
The driver has been adapted to U-Boot and the ADC UClass.

This patch depends on the regmap "regmap: add regmap_update_bits() helper"
patch and has been tested using the newly introducted "adc" CLI command
in the "cmd: add ADC cli commands" patch.

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>

3 files changed, 734 insertions, 0 deletions

diff --git a/drivers/adc/Kconfig b/drivers/adc/Kconfig
index 8094420548..93e27f131c 100644
--- a/drivers/adc/Kconfig
+++ b/drivers/adc/Kconfig
@@ -29,6 +29,16 @@ config ADC_SANDBOX
 	  - 16-bit resolution
 	  - single and multi-channel conversion mode
 
+config SARADC_MESON
+	bool "Enable Amlogic Meson SARADC driver"
+	imply REGMAP
+	help
+	  This enables driver for Amlogic Meson SARADC.
+	  It provides:
+	  - 8 analog input channels
+	  - 1O or 12 bits resolution
+	  - Up to 1MSPS of sample rate
+
 config SARADC_ROCKCHIP
 	bool "Enable Rockchip SARADC driver"
 	help
diff --git a/drivers/adc/Makefile b/drivers/adc/Makefile
index 4b5aa693ec..95c93d4c57 100644
--- a/drivers/adc/Makefile
+++ b/drivers/adc/Makefile
@@ -9,3 +9,4 @@ obj-$(CONFIG_ADC) += adc-uclass.o
 obj-$(CONFIG_ADC_EXYNOS) += exynos-adc.o
 obj-$(CONFIG_ADC_SANDBOX) += sandbox.o
 obj-$(CONFIG_SARADC_ROCKCHIP) += rockchip-saradc.o
+obj-$(CONFIG_SARADC_MESON) += meson-saradc.o
diff --git a/drivers/adc/meson-saradc.c b/drivers/adc/meson-saradc.c
new file mode 100644
index 0000000000..bcab76d050
--- /dev/null
+++ b/drivers/adc/meson-saradc.c
@@ -0,0 +1,723 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2017 Martin Blumenstingl <martin.blumenstingl@googlemail.com>
+ * Copyright (C) 2018 BayLibre, SAS
+ * Author: Neil Armstrong <narmstrong@baylibre.com>
+ *
+ * Amlogic Meson Successive Approximation Register (SAR) A/D Converter
+ */
+
+#include <common.h>
+#include <adc.h>
+#include <clk.h>
+#include <dm.h>
+#include <regmap.h>
+#include <errno.h>
+#include <asm/io.h>
+#include <linux/math64.h>
+#include <linux/bitfield.h>
+
+#define MESON_SAR_ADC_REG0					0x00
+	#define MESON_SAR_ADC_REG0_PANEL_DETECT			BIT(31)
+	#define MESON_SAR_ADC_REG0_BUSY_MASK			GENMASK(30, 28)
+	#define MESON_SAR_ADC_REG0_DELTA_BUSY			BIT(30)
+	#define MESON_SAR_ADC_REG0_AVG_BUSY			BIT(29)
+	#define MESON_SAR_ADC_REG0_SAMPLE_BUSY			BIT(28)
+	#define MESON_SAR_ADC_REG0_FIFO_FULL			BIT(27)
+	#define MESON_SAR_ADC_REG0_FIFO_EMPTY			BIT(26)
+	#define MESON_SAR_ADC_REG0_FIFO_COUNT_MASK		GENMASK(25, 21)
+	#define MESON_SAR_ADC_REG0_ADC_BIAS_CTRL_MASK		GENMASK(20, 19)
+	#define MESON_SAR_ADC_REG0_CURR_CHAN_ID_MASK		GENMASK(18, 16)
+	#define MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL		BIT(15)
+	#define MESON_SAR_ADC_REG0_SAMPLING_STOP		BIT(14)
+	#define MESON_SAR_ADC_REG0_CHAN_DELTA_EN_MASK		GENMASK(13, 12)
+	#define MESON_SAR_ADC_REG0_DETECT_IRQ_POL		BIT(10)
+	#define MESON_SAR_ADC_REG0_DETECT_IRQ_EN		BIT(9)
+	#define MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK		GENMASK(8, 4)
+	#define MESON_SAR_ADC_REG0_FIFO_IRQ_EN			BIT(3)
+	#define MESON_SAR_ADC_REG0_SAMPLING_START		BIT(2)
+	#define MESON_SAR_ADC_REG0_CONTINUOUS_EN		BIT(1)
+	#define MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE		BIT(0)
+
+#define MESON_SAR_ADC_CHAN_LIST					0x04
+	#define MESON_SAR_ADC_CHAN_LIST_MAX_INDEX_MASK		GENMASK(26, 24)
+	#define MESON_SAR_ADC_CHAN_LIST_ENTRY_MASK(_chan)	\
+					(GENMASK(2, 0) << ((_chan) * 3))
+
+#define MESON_SAR_ADC_AVG_CNTL					0x08
+	#define MESON_SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(_chan)	\
+					(16 + ((_chan) * 2))
+	#define MESON_SAR_ADC_AVG_CNTL_AVG_MODE_MASK(_chan)	\
+					(GENMASK(17, 16) << ((_chan) * 2))
+	#define MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(_chan)	\
+					(0 + ((_chan) * 2))
+	#define MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(_chan)	\
+					(GENMASK(1, 0) << ((_chan) * 2))
+
+#define MESON_SAR_ADC_REG3					0x0c
+	#define MESON_SAR_ADC_REG3_CNTL_USE_SC_DLY		BIT(31)
+	#define MESON_SAR_ADC_REG3_CLK_EN			BIT(30)
+	#define MESON_SAR_ADC_REG3_BL30_INITIALIZED		BIT(28)
+	#define MESON_SAR_ADC_REG3_CTRL_CONT_RING_COUNTER_EN	BIT(27)
+	#define MESON_SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE	BIT(26)
+	#define MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK	GENMASK(25, 23)
+	#define MESON_SAR_ADC_REG3_DETECT_EN			BIT(22)
+	#define MESON_SAR_ADC_REG3_ADC_EN			BIT(21)
+	#define MESON_SAR_ADC_REG3_PANEL_DETECT_COUNT_MASK	GENMASK(20, 18)
+	#define MESON_SAR_ADC_REG3_PANEL_DETECT_FILTER_TB_MASK	GENMASK(17, 16)
+	#define MESON_SAR_ADC_REG3_ADC_CLK_DIV_SHIFT		10
+	#define MESON_SAR_ADC_REG3_ADC_CLK_DIV_WIDTH		5
+	#define MESON_SAR_ADC_REG3_BLOCK_DLY_SEL_MASK		GENMASK(9, 8)
+	#define MESON_SAR_ADC_REG3_BLOCK_DLY_MASK		GENMASK(7, 0)
+
+#define MESON_SAR_ADC_DELAY					0x10
+	#define MESON_SAR_ADC_DELAY_INPUT_DLY_SEL_MASK		GENMASK(25, 24)
+	#define MESON_SAR_ADC_DELAY_BL30_BUSY			BIT(15)
+	#define MESON_SAR_ADC_DELAY_KERNEL_BUSY			BIT(14)
+	#define MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK		GENMASK(23, 16)
+	#define MESON_SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK		GENMASK(9, 8)
+	#define MESON_SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK		GENMASK(7, 0)
+
+#define MESON_SAR_ADC_LAST_RD					0x14
+	#define MESON_SAR_ADC_LAST_RD_LAST_CHANNEL1_MASK	GENMASK(23, 16)
+	#define MESON_SAR_ADC_LAST_RD_LAST_CHANNEL0_MASK	GENMASK(9, 0)
+
+#define MESON_SAR_ADC_FIFO_RD					0x18
+	#define MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK		GENMASK(14, 12)
+	#define MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK		GENMASK(11, 0)
+
+#define MESON_SAR_ADC_AUX_SW					0x1c
+	#define MESON_SAR_ADC_AUX_SW_MUX_SEL_CHAN_SHIFT(_chan)	\
+					(8 + (((_chan) - 2) * 3))
+	#define MESON_SAR_ADC_AUX_SW_VREF_P_MUX			BIT(6)
+	#define MESON_SAR_ADC_AUX_SW_VREF_N_MUX			BIT(5)
+	#define MESON_SAR_ADC_AUX_SW_MODE_SEL			BIT(4)
+	#define MESON_SAR_ADC_AUX_SW_YP_DRIVE_SW		BIT(3)
+	#define MESON_SAR_ADC_AUX_SW_XP_DRIVE_SW		BIT(2)
+	#define MESON_SAR_ADC_AUX_SW_YM_DRIVE_SW		BIT(1)
+	#define MESON_SAR_ADC_AUX_SW_XM_DRIVE_SW		BIT(0)
+
+#define MESON_SAR_ADC_CHAN_10_SW				0x20
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK	GENMASK(25, 23)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_VREF_P_MUX	BIT(22)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_VREF_N_MUX	BIT(21)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_MODE_SEL		BIT(20)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_YP_DRIVE_SW	BIT(19)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_XP_DRIVE_SW	BIT(18)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_YM_DRIVE_SW	BIT(17)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN1_XM_DRIVE_SW	BIT(16)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK	GENMASK(9, 7)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_VREF_P_MUX	BIT(6)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_VREF_N_MUX	BIT(5)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_MODE_SEL		BIT(4)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_YP_DRIVE_SW	BIT(3)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_XP_DRIVE_SW	BIT(2)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_YM_DRIVE_SW	BIT(1)
+	#define MESON_SAR_ADC_CHAN_10_SW_CHAN0_XM_DRIVE_SW	BIT(0)
+
+#define MESON_SAR_ADC_DETECT_IDLE_SW				0x24
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_SW_EN	BIT(26)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MUX_MASK	GENMASK(25, 23)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_VREF_P_MUX	BIT(22)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_VREF_N_MUX	BIT(21)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MODE_SEL	BIT(20)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_YP_DRIVE_SW	BIT(19)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_XP_DRIVE_SW	BIT(18)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_YM_DRIVE_SW	BIT(17)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_XM_DRIVE_SW	BIT(16)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK	GENMASK(9, 7)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_VREF_P_MUX	BIT(6)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_VREF_N_MUX	BIT(5)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MODE_SEL	BIT(4)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_YP_DRIVE_SW	BIT(3)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_XP_DRIVE_SW	BIT(2)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_YM_DRIVE_SW	BIT(1)
+	#define MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_XM_DRIVE_SW	BIT(0)
+
+#define MESON_SAR_ADC_DELTA_10					0x28
+	#define MESON_SAR_ADC_DELTA_10_TEMP_SEL			BIT(27)
+	#define MESON_SAR_ADC_DELTA_10_TS_REVE1			BIT(26)
+	#define MESON_SAR_ADC_DELTA_10_CHAN1_DELTA_VALUE_MASK	GENMASK(25, 16)
+	#define MESON_SAR_ADC_DELTA_10_TS_REVE0			BIT(15)
+	#define MESON_SAR_ADC_DELTA_10_TS_C_SHIFT		11
+	#define MESON_SAR_ADC_DELTA_10_TS_C_MASK		GENMASK(14, 11)
+	#define MESON_SAR_ADC_DELTA_10_TS_VBG_EN		BIT(10)
+	#define MESON_SAR_ADC_DELTA_10_CHAN0_DELTA_VALUE_MASK	GENMASK(9, 0)
+
+/*
+ * NOTE: registers from here are undocumented (the vendor Linux kernel driver
+ * and u-boot source served as reference). These only seem to be relevant on
+ * GXBB and newer.
+ */
+#define MESON_SAR_ADC_REG11					0x2c
+	#define MESON_SAR_ADC_REG11_BANDGAP_EN			BIT(13)
+
+#define MESON_SAR_ADC_REG13					0x34
+	#define MESON_SAR_ADC_REG13_12BIT_CALIBRATION_MASK	GENMASK(13, 8)
+
+#define MESON_SAR_ADC_MAX_FIFO_SIZE				32
+#define MESON_SAR_ADC_TIMEOUT					100 /* ms */
+
+#define NUM_CHANNELS						8
+
+#define MILLION							1000000
+
+struct meson_saradc_data {
+	int				num_bits;
+};
+
+struct meson_saradc_priv {
+	const struct meson_saradc_data	*data;
+	struct regmap			*regmap;
+	struct clk			core_clk;
+	struct clk			adc_clk;
+	bool				initialized;
+	int				active_channel;
+	int				calibbias;
+	int				calibscale;
+};
+
+static unsigned int
+meson_saradc_get_fifo_count(struct meson_saradc_priv *priv)
+{
+	u32 regval;
+
+	regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+
+	return FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
+}
+
+static int meson_saradc_lock(struct meson_saradc_priv *priv)
+{
+	uint val, timeout = 10000;
+
+	/* prevent BL30 from using the SAR ADC while we are using it */
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
+			   MESON_SAR_ADC_DELAY_KERNEL_BUSY,
+			   MESON_SAR_ADC_DELAY_KERNEL_BUSY);
+
+	/*
+	 * wait until BL30 releases it's lock (so we can use the SAR ADC)
+	 */
+	do {
+		udelay(1);
+		regmap_read(priv->regmap, MESON_SAR_ADC_DELAY, &val);
+	} while (val & MESON_SAR_ADC_DELAY_BL30_BUSY && timeout--);
+
+	if (timeout < 0) {
+		printf("Timeout while waiting for BL30 unlock\n");
+		return -ETIMEDOUT;
+	}
+
+	return 0;
+}
+
+static void meson_saradc_unlock(struct meson_saradc_priv *priv)
+{
+	/* allow BL30 to use the SAR ADC again */
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
+			   MESON_SAR_ADC_DELAY_KERNEL_BUSY, 0);
+}
+
+static void meson_saradc_clear_fifo(struct meson_saradc_priv *priv)
+{
+	unsigned int count, tmp;
+
+	for (count = 0; count < MESON_SAR_ADC_MAX_FIFO_SIZE; count++) {
+		if (!meson_saradc_get_fifo_count(priv))
+			break;
+
+		regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &tmp);
+	}
+}
+
+static int meson_saradc_calib_val(struct meson_saradc_priv *priv, int val)
+{
+	int tmp;
+
+	/* use val_calib = scale * val_raw + offset calibration function */
+	tmp = div_s64((s64)val * priv->calibscale, MILLION) + priv->calibbias;
+
+	return clamp(tmp, 0, (1 << priv->data->num_bits) - 1);
+}
+
+static int meson_saradc_wait_busy_clear(struct meson_saradc_priv *priv)
+{
+	uint regval, timeout = 10000;
+
+	/*
+	 * NOTE: we need a small delay before reading the status, otherwise
+	 * the sample engine may not have started internally (which would
+	 * seem to us that sampling is already finished).
+	 */
+	do {
+		udelay(1);
+		regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+	} while (FIELD_GET(MESON_SAR_ADC_REG0_BUSY_MASK, regval) && timeout--);
+
+	if (timeout < 0)
+		return -ETIMEDOUT;
+
+	return 0;
+}
+
+static int meson_saradc_read_raw_sample(struct meson_saradc_priv *priv,
+					unsigned int channel, uint *val)
+{
+	uint regval, fifo_chan, fifo_val, count;
+	int ret;
+
+	ret = meson_saradc_wait_busy_clear(priv);
+	if (ret)
+		return ret;
+
+	count = meson_saradc_get_fifo_count(priv);
+	if (count != 1) {
+		printf("ADC FIFO has %d element(s) instead of one\n", count);
+		return -EINVAL;
+	}
+
+	regmap_read(priv->regmap, MESON_SAR_ADC_FIFO_RD, &regval);
+	fifo_chan = FIELD_GET(MESON_SAR_ADC_FIFO_RD_CHAN_ID_MASK, regval);
+	if (fifo_chan != channel) {
+		printf("ADC FIFO entry belongs to channel %d instead of %d\n",
+		       fifo_chan, channel);
+		return -EINVAL;
+	}
+
+	fifo_val = FIELD_GET(MESON_SAR_ADC_FIFO_RD_SAMPLE_VALUE_MASK, regval);
+	fifo_val &= GENMASK(priv->data->num_bits - 1, 0);
+	*val = meson_saradc_calib_val(priv, fifo_val);
+
+	return 0;
+}
+
+static void meson_saradc_start_sample_engine(struct meson_saradc_priv *priv)
+{
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_FIFO_IRQ_EN,
+			   MESON_SAR_ADC_REG0_FIFO_IRQ_EN);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE,
+			   MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_SAMPLING_START,
+			   MESON_SAR_ADC_REG0_SAMPLING_START);
+}
+
+static void meson_saradc_stop_sample_engine(struct meson_saradc_priv *priv)
+{
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_FIFO_IRQ_EN, 0);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_SAMPLING_STOP,
+			   MESON_SAR_ADC_REG0_SAMPLING_STOP);
+
+	/* wait until all modules are stopped */
+	meson_saradc_wait_busy_clear(priv);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_SAMPLE_ENGINE_ENABLE, 0);
+}
+
+enum meson_saradc_avg_mode {
+	NO_AVERAGING = 0x0,
+	MEAN_AVERAGING = 0x1,
+	MEDIAN_AVERAGING = 0x2,
+};
+
+enum meson_saradc_num_samples {
+	ONE_SAMPLE = 0x0,
+	TWO_SAMPLES = 0x1,
+	FOUR_SAMPLES = 0x2,
+	EIGHT_SAMPLES = 0x3,
+};
+
+static void meson_saradc_set_averaging(struct meson_saradc_priv *priv,
+				       unsigned int channel,
+				       enum meson_saradc_avg_mode mode,
+				       enum meson_saradc_num_samples samples)
+{
+	int val;
+
+	val = samples << MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_SHIFT(channel);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_AVG_CNTL,
+			   MESON_SAR_ADC_AVG_CNTL_NUM_SAMPLES_MASK(channel),
+			   val);
+
+	val = mode << MESON_SAR_ADC_AVG_CNTL_AVG_MODE_SHIFT(channel);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_AVG_CNTL,
+			   MESON_SAR_ADC_AVG_CNTL_AVG_MODE_MASK(channel), val);
+}
+
+static void meson_saradc_enable_channel(struct meson_saradc_priv *priv,
+					unsigned int channel)
+{
+	uint regval;
+
+	/*
+	 * the SAR ADC engine allows sampling multiple channels at the same
+	 * time. to keep it simple we're only working with one *internal*
+	 * channel, which starts counting at index 0 (which means: count = 1).
+	 */
+	regval = FIELD_PREP(MESON_SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, 0);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_CHAN_LIST,
+			   MESON_SAR_ADC_CHAN_LIST_MAX_INDEX_MASK, regval);
+
+	/* map channel index 0 to the channel which we want to read */
+	regval = FIELD_PREP(MESON_SAR_ADC_CHAN_LIST_ENTRY_MASK(0), channel);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_CHAN_LIST,
+			   MESON_SAR_ADC_CHAN_LIST_ENTRY_MASK(0), regval);
+
+	regval = FIELD_PREP(MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MUX_MASK,
+			    channel);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DETECT_IDLE_SW,
+			   MESON_SAR_ADC_DETECT_IDLE_SW_DETECT_MUX_MASK,
+			   regval);
+
+	regval = FIELD_PREP(MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK,
+			    channel);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DETECT_IDLE_SW,
+			   MESON_SAR_ADC_DETECT_IDLE_SW_IDLE_MUX_SEL_MASK,
+			   regval);
+
+	if (channel == 6)
+		regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELTA_10,
+				   MESON_SAR_ADC_DELTA_10_TEMP_SEL, 0);
+}
+
+static int meson_saradc_get_sample(struct meson_saradc_priv *priv,
+				   int chan, uint *val)
+{
+	int ret;
+
+	ret = meson_saradc_lock(priv);
+	if (ret)
+		return ret;
+
+	/* clear the FIFO to make sure we're not reading old values */
+	meson_saradc_clear_fifo(priv);
+
+	meson_saradc_set_averaging(priv, chan, MEAN_AVERAGING, EIGHT_SAMPLES);
+
+	meson_saradc_enable_channel(priv, chan);
+
+	meson_saradc_start_sample_engine(priv);
+	ret = meson_saradc_read_raw_sample(priv, chan, val);
+	meson_saradc_stop_sample_engine(priv);
+
+	meson_saradc_unlock(priv);
+
+	if (ret) {
+		printf("failed to read sample for channel %d: %d\n",
+		       chan, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int meson_saradc_channel_data(struct udevice *dev, int channel,
+				     unsigned int *data)
+{
+	struct meson_saradc_priv *priv = dev_get_priv(dev);
+
+	if (channel != priv->active_channel) {
+		pr_err("Requested channel is not active!");
+		return -EINVAL;
+	}
+
+	return meson_saradc_get_sample(priv, channel, data);
+}
+
+enum meson_saradc_chan7_mux_sel {
+	CHAN7_MUX_VSS = 0x0,
+	CHAN7_MUX_VDD_DIV4 = 0x1,
+	CHAN7_MUX_VDD_DIV2 = 0x2,
+	CHAN7_MUX_VDD_MUL3_DIV4 = 0x3,
+	CHAN7_MUX_VDD = 0x4,
+	CHAN7_MUX_CH7_INPUT = 0x7,
+};
+
+static void meson_saradc_set_chan7_mux(struct meson_saradc_priv *priv,
+				       enum meson_saradc_chan7_mux_sel sel)
+{
+	u32 regval;
+
+	regval = FIELD_PREP(MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, sel);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
+			   MESON_SAR_ADC_REG3_CTRL_CHAN7_MUX_SEL_MASK, regval);
+
+	udelay(20);
+}
+
+static int meson_saradc_calib(struct meson_saradc_priv *priv)
+{
+	uint nominal0, nominal1, value0, value1;
+	int ret;
+
+	/* use points 25% and 75% for calibration */
+	nominal0 = (1 << priv->data->num_bits) / 4;
+	nominal1 = (1 << priv->data->num_bits) * 3 / 4;
+
+	meson_saradc_set_chan7_mux(priv, CHAN7_MUX_VDD_DIV4);
+	udelay(20);
+	ret = meson_saradc_get_sample(priv, 7, &value0);
+	if (ret < 0)
+		goto out;
+
+	meson_saradc_set_chan7_mux(priv, CHAN7_MUX_VDD_MUL3_DIV4);
+	udelay(20);
+	ret = meson_saradc_get_sample(priv, 7, &value1);
+	if (ret < 0)
+		goto out;
+
+	if (value1 <= value0) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	priv->calibscale = div_s64((nominal1 - nominal0) * (s64)MILLION,
+				   value1 - value0);
+	priv->calibbias = nominal0 - div_s64((s64)value0 * priv->calibscale,
+					     MILLION);
+	ret = 0;
+out:
+	meson_saradc_set_chan7_mux(priv, CHAN7_MUX_CH7_INPUT);
+
+	return ret;
+}
+
+static int meson_saradc_init(struct meson_saradc_priv *priv)
+{
+	uint regval;
+	int ret, i;
+
+	priv->calibscale = MILLION;
+
+	/*
+	 * make sure we start at CH7 input since the other muxes are only used
+	 * for internal calibration.
+	 */
+	meson_saradc_set_chan7_mux(priv, CHAN7_MUX_CH7_INPUT);
+
+	/*
+	 * leave sampling delay and the input clocks as configured by
+	 * BL30 to make sure BL30 gets the values it expects when
+	 * reading the temperature sensor.
+	 */
+	regmap_read(priv->regmap, MESON_SAR_ADC_REG3, &regval);
+	if (regval & MESON_SAR_ADC_REG3_BL30_INITIALIZED)
+		return 0;
+
+	meson_saradc_stop_sample_engine(priv);
+
+	/* update the channel 6 MUX to select the temperature sensor */
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL,
+			   MESON_SAR_ADC_REG0_ADC_TEMP_SEN_SEL);
+
+	/* disable all channels by default */
+	regmap_write(priv->regmap, MESON_SAR_ADC_CHAN_LIST, 0x0);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
+			   MESON_SAR_ADC_REG3_CTRL_SAMPLING_CLOCK_PHASE, 0);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
+			   MESON_SAR_ADC_REG3_CNTL_USE_SC_DLY,
+			   MESON_SAR_ADC_REG3_CNTL_USE_SC_DLY);
+
+	/* delay between two samples = (10+1) * 1uS */
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
+			   MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
+			   FIELD_PREP(MESON_SAR_ADC_DELAY_SAMPLE_DLY_CNT_MASK,
+				      10));
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
+			   MESON_SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
+			   FIELD_PREP(MESON_SAR_ADC_DELAY_SAMPLE_DLY_SEL_MASK,
+				      0));
+
+	/* delay between two samples = (10+1) * 1uS */
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
+			   MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
+			   FIELD_PREP(MESON_SAR_ADC_DELAY_INPUT_DLY_CNT_MASK,
+				      10));
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_DELAY,
+			   MESON_SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
+			   FIELD_PREP(MESON_SAR_ADC_DELAY_INPUT_DLY_SEL_MASK,
+				      1));
+
+	/*
+	 * set up the input channel muxes in MESON_SAR_ADC_CHAN_10_SW
+	 * (0 = SAR_ADC_CH0, 1 = SAR_ADC_CH1)
+	 */
+	regval = FIELD_PREP(MESON_SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK, 0);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_CHAN_10_SW,
+			   MESON_SAR_ADC_CHAN_10_SW_CHAN0_MUX_SEL_MASK,
+			   regval);
+	regval = FIELD_PREP(MESON_SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK, 1);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_CHAN_10_SW,
+			   MESON_SAR_ADC_CHAN_10_SW_CHAN1_MUX_SEL_MASK,
+			   regval);
+
+	/*
+	 * set up the input channel muxes in MESON_SAR_ADC_AUX_SW
+	 * (2 = SAR_ADC_CH2, 3 = SAR_ADC_CH3, ...) and enable
+	 * MESON_SAR_ADC_AUX_SW_YP_DRIVE_SW and
+	 * MESON_SAR_ADC_AUX_SW_XP_DRIVE_SW like the vendor driver.
+	 */
+	regval = 0;
+	for (i = 2; i <= 7; i++)
+		regval |= i << MESON_SAR_ADC_AUX_SW_MUX_SEL_CHAN_SHIFT(i);
+	regval |= MESON_SAR_ADC_AUX_SW_YP_DRIVE_SW;
+	regval |= MESON_SAR_ADC_AUX_SW_XP_DRIVE_SW;
+	regmap_write(priv->regmap, MESON_SAR_ADC_AUX_SW, regval);
+
+	ret = meson_saradc_lock(priv);
+	if (ret)
+		return ret;
+
+#if CONFIG_IS_ENABLED(CLK)
+	ret = clk_enable(&priv->core_clk);
+	if (ret)
+		return ret;
+#endif
+
+	regval = FIELD_PREP(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, 1);
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG0,
+			   MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG11,
+			   MESON_SAR_ADC_REG11_BANDGAP_EN,
+			   MESON_SAR_ADC_REG11_BANDGAP_EN);
+
+	regmap_update_bits(priv->regmap, MESON_SAR_ADC_REG3,
+			   MESON_SAR_ADC_REG3_ADC_EN,
+			   MESON_SAR_ADC_REG3_ADC_EN);
+
+	udelay(5);
+
+#if CONFIG_IS_ENABLED(CLK)
+	ret = clk_enable(&priv->adc_clk);
+	if (ret)
+		return ret;
+#endif
+
+	meson_saradc_unlock(priv);
+
+	ret = meson_saradc_calib(priv);
+	if (ret) {
+		printf("calibration failed\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int meson_saradc_start_channel(struct udevice *dev, int channel)
+{
+	struct meson_saradc_priv *priv = dev_get_priv(dev);
+
+	if (channel < 0 || channel >= NUM_CHANNELS) {
+		printf("Requested channel is invalid!");
+		return -EINVAL;
+	}
+
+	if (!priv->initialized) {
+		int ret;
+
+		ret = meson_saradc_init(priv);
+		if (ret)
+			return ret;
+
+		priv->initialized = true;
+	}
+
+	priv->active_channel = channel;
+
+	return 0;
+}
+
+static int meson_saradc_stop(struct udevice *dev)
+{
+	struct meson_saradc_priv *priv = dev_get_priv(dev);
+
+	priv->active_channel = -1;
+
+	return 0;
+}
+
+static int meson_saradc_probe(struct udevice *dev)
+{
+	struct meson_saradc_priv *priv = dev_get_priv(dev);
+	int ret;
+
+	ret = regmap_init_mem(dev, &priv->regmap);
+	if (ret)
+		return ret;
+
+#if CONFIG_IS_ENABLED(CLK)
+	ret = clk_get_by_name(dev, "core", &priv->core_clk);
+	if (ret)
+		return ret;
+
+	ret = clk_get_by_name(dev, "adc_clk", &priv->adc_clk);
+	if (ret)
+		return ret;
+#endif
+
+	priv->active_channel = -1;
+
+	return 0;
+}
+
+int meson_saradc_ofdata_to_platdata(struct udevice *dev)
+{
+	struct adc_uclass_platdata *uc_pdata = dev_get_uclass_platdata(dev);
+	struct meson_saradc_priv *priv = dev_get_priv(dev);
+
+	priv->data = (struct meson_saradc_data *)dev_get_driver_data(dev);
+
+	uc_pdata->data_mask = GENMASK(priv->data->num_bits - 1, 0);
+	uc_pdata->data_format = ADC_DATA_FORMAT_BIN;
+	uc_pdata->data_timeout_us = MESON_SAR_ADC_TIMEOUT * 1000;
+	uc_pdata->channel_mask = GENMASK(NUM_CHANNELS - 1, 0);
+
+	return 0;
+}
+
+static const struct adc_ops meson_saradc_ops = {
+	.start_channel = meson_saradc_start_channel,
+	.channel_data = meson_saradc_channel_data,
+	.stop = meson_saradc_stop,
+};
+
+static const struct meson_saradc_data gxbb_saradc_data = {
+	.num_bits = 10,
+};
+
+static const struct meson_saradc_data gxl_saradc_data = {
+	.num_bits = 12,
+};
+
+static const struct udevice_id meson_saradc_ids[] = {
+	{ .compatible = "amlogic,meson-gxbb-saradc",
+	  .data = (ulong)&gxbb_saradc_data },
+	{ .compatible = "amlogic,meson-gxl-saradc",
+	  .data = (ulong)&gxl_saradc_data },
+	{ .compatible = "amlogic,meson-gxm-saradc",
+	  .data = (ulong)&gxl_saradc_data },
+	{ }
+};
+
+U_BOOT_DRIVER(meson_saradc) = {
+	.name		= "meson_saradc",
+	.id		= UCLASS_ADC,
+	.of_match	= meson_saradc_ids,
+	.ops		= &meson_saradc_ops,
+	.probe		= meson_saradc_probe,
+	.ofdata_to_platdata = meson_saradc_ofdata_to_platdata,
+	.priv_auto_alloc_size = sizeof(struct meson_saradc_priv),
+};