[PATCH v2 1/2] iio: adc: meson-saradc: switch from polling to interrupt mode

[Heiner Kallweit <hkallweit1@gmail.com>]

Switch from polling to interrupt mode.

Successfully tested on a S905GXBB-based Odroid C2.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
---
v2:
- move enabling / disabling irq to meson_sar_adc_start_sample_engine /
  meson_sar_adc_stop_sample_engine respectively
- move setting FIFO threshold for irq triggering to meson_sar_adc_hw_enable
  to avoid a potential issue when uboot should be involved in system resume
- return IRQ_NONE if the interrupt can't be for us
- document interrupts property in DT documentation
---
 .../bindings/iio/adc/amlogic,meson-saradc.txt      |  2 +
 drivers/iio/adc/meson_saradc.c                     | 56 ++++++++++++++++++++--
 2 files changed, 53 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt b/Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt
index f9e3ff2c..04718919 100644
--- a/Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt
+++ b/Documentation/devicetree/bindings/iio/adc/amlogic,meson-saradc.txt
@@ -7,6 +7,7 @@ Required properties:
 			- "amlogic,meson-gxm-saradc" for GXM
 		along with the generic "amlogic,meson-saradc"
 - reg:		the physical base address and length of the registers
+- interrupts:	the interrupt indicating end of sampling
 - clocks:	phandle and clock identifier (see clock-names)
 - clock-names:	mandatory clocks:
 			- "clkin" for the reference clock (typically XTAL)
@@ -23,6 +24,7 @@ Example:
 		compatible = "amlogic,meson-gxl-saradc", "amlogic,meson-saradc";
 		#io-channel-cells = <1>;
 		reg = <0x0 0x8680 0x0 0x34>;
+		interrupts = <GIC_SPI 73 IRQ_TYPE_EDGE_RISING>;
 		clocks = <&xtal>,
 			 <&clkc CLKID_SAR_ADC>,
 			 <&clkc CLKID_SANA>,
diff --git a/drivers/iio/adc/meson_saradc.c b/drivers/iio/adc/meson_saradc.c
index 89def603..9f186de2 100644
--- a/drivers/iio/adc/meson_saradc.c
+++ b/drivers/iio/adc/meson_saradc.c
@@ -18,7 +18,9 @@
 #include <linux/io.h>
 #include <linux/iio/iio.h>
 #include <linux/module.h>
+#include <linux/interrupt.h>
 #include <linux/of.h>
+#include <linux/of_irq.h>
 #include <linux/of_device.h>
 #include <linux/platform_device.h>
 #include <linux/regmap.h>
@@ -163,6 +165,7 @@
 	#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 MESON_SAR_ADC_CHAN(_chan) {					\
 	.type = IIO_VOLTAGE,						\
@@ -229,6 +232,7 @@ struct meson_sar_adc_priv {
 	struct clk_gate				clk_gate;
 	struct clk				*adc_div_clk;
 	struct clk_divider			clk_div;
+	struct completion			done;
 };
 
 static const struct regmap_config meson_sar_adc_regmap_config = {
@@ -274,11 +278,11 @@ static int meson_sar_adc_read_raw_sample(struct iio_dev *indio_dev,
 					 int *val)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
-	int ret, regval, fifo_chan, fifo_val, sum = 0, count = 0;
+	int regval, fifo_chan, fifo_val, sum = 0, count = 0;
 
-	ret = meson_sar_adc_wait_busy_clear(indio_dev);
-	if (ret)
-		return ret;
+	if(!wait_for_completion_timeout(&priv->done,
+				msecs_to_jiffies(MESON_SAR_ADC_TIMEOUT)))
+		return -ETIMEDOUT;
 
 	while (meson_sar_adc_get_fifo_count(indio_dev) > 0 &&
 	       count < MESON_SAR_ADC_MAX_FIFO_SIZE) {
@@ -378,6 +382,12 @@ static void meson_sar_adc_start_sample_engine(struct iio_dev *indio_dev)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 
+	reinit_completion(&priv->done);
+
+	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);
@@ -392,6 +402,9 @@ static void meson_sar_adc_stop_sample_engine(struct iio_dev *indio_dev)
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 
 	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);
 
@@ -643,6 +656,7 @@ static int meson_sar_adc_hw_enable(struct iio_dev *indio_dev)
 {
 	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
 	int ret;
+	u32 regval;
 
 	ret = meson_sar_adc_lock(indio_dev);
 	if (ret)
@@ -667,6 +681,9 @@ static int meson_sar_adc_hw_enable(struct iio_dev *indio_dev)
 		goto err_sana_clk;
 	}
 
+	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);
@@ -728,6 +745,25 @@ static int meson_sar_adc_hw_disable(struct iio_dev *indio_dev)
 	return 0;
 }
 
+static irqreturn_t meson_sar_adc_irq(int irq, void *data)
+{
+	struct iio_dev *indio_dev = data;
+	struct meson_sar_adc_priv *priv = iio_priv(indio_dev);
+	unsigned int cnt, threshold;
+	u32 regval;
+
+	regmap_read(priv->regmap, MESON_SAR_ADC_REG0, &regval);
+	cnt = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_COUNT_MASK, regval);
+	threshold = FIELD_GET(MESON_SAR_ADC_REG0_FIFO_CNT_IRQ_MASK, regval);
+
+	if (cnt < threshold)
+		return IRQ_NONE;
+
+	complete(&priv->done);
+
+	return IRQ_HANDLED;
+}
+
 static const struct iio_info meson_sar_adc_iio_info = {
 	.read_raw = meson_sar_adc_iio_info_read_raw,
 	.driver_module = THIS_MODULE,
@@ -770,7 +806,7 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	struct resource *res;
 	void __iomem *base;
 	const struct of_device_id *match;
-	int ret;
+	int irq, ret;
 
 	indio_dev = devm_iio_device_alloc(&pdev->dev, sizeof(*priv));
 	if (!indio_dev) {
@@ -779,6 +815,7 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	}
 
 	priv = iio_priv(indio_dev);
+	init_completion(&priv->done);
 
 	match = of_match_device(meson_sar_adc_of_match, &pdev->dev);
 	priv->data = match->data;
@@ -797,6 +834,15 @@ static int meson_sar_adc_probe(struct platform_device *pdev)
 	if (IS_ERR(base))
 		return PTR_ERR(base);
 
+	irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
+	if (!irq)
+		return -EINVAL;
+
+	ret = devm_request_irq(&pdev->dev, irq, meson_sar_adc_irq, IRQF_SHARED,
+			       dev_name(&pdev->dev), indio_dev);
+	if (ret)
+		return ret;
+
 	priv->regmap = devm_regmap_init_mmio(&pdev->dev, base,
 					     &meson_sar_adc_regmap_config);
 	if (IS_ERR(priv->regmap))
-- 
2.11.1