stm32 adc supports several resolution. Add 'assigned-resolution-bits'
dt optional property to set it. Default to maximum resolution in case
it isn't set.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
---
Changes in v2:
- rename property from 'st,adc-res' to 'assigned-resolution-bits', so it
is more common.
---
drivers/iio/adc/stm32-adc.c | 50 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 49 insertions(+), 1 deletion(-)
diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 9b49a6ad..c28e7ff 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -60,6 +60,8 @@
#define STM32F4_EOC BIT(1)
/* STM32F4_ADC_CR1 - bit fields */
+#define STM32F4_RES_SHIFT 24
+#define STM32F4_RES_MASK GENMASK(25, 24)
#define STM32F4_SCAN BIT(8)
#define STM32F4_EOCIE BIT(5)
@@ -141,6 +143,7 @@ struct stm32_adc_regs {
* @lock: spinlock
* @bufi: data buffer index
* @num_conv: expected number of scan conversions
+ * @res: data resolution (e.g. RES bitfield value)
* @trigger_polarity: external trigger polarity (e.g. exten)
* @dma_chan: dma channel
* @rx_buf: dma rx buffer cpu address
@@ -157,6 +160,7 @@ struct stm32_adc {
spinlock_t lock; /* interrupt lock */
unsigned int bufi;
unsigned int num_conv;
+ u32 res;
u32 trigger_polarity;
struct dma_chan *dma_chan;
u8 *rx_buf;
@@ -196,6 +200,11 @@ struct stm32_adc_chan_spec {
{ IIO_VOLTAGE, 15, "in15" },
};
+static const unsigned int stm32f4_adc_resolutions[] = {
+ /* sorted values so the index matches RES[1:0] in STM32F4_ADC_CR1 */
+ 12, 10, 8, 6,
+};
+
/**
* stm32f4_sq - describe regular sequence registers
* - L: sequence len (register & bit field)
@@ -302,6 +311,14 @@ static void stm32_adc_conv_irq_disable(struct stm32_adc *adc)
stm32_adc_clr_bits(adc, STM32F4_ADC_CR1, STM32F4_EOCIE);
}
+static void stm32_adc_set_res(struct stm32_adc *adc)
+{
+ u32 val = stm32_adc_readl(adc, STM32F4_ADC_CR1);
+
+ val = (val & ~STM32F4_RES_MASK) | (adc->res << STM32F4_RES_SHIFT);
+ stm32_adc_writel(adc, STM32F4_ADC_CR1, val);
+}
+
/**
* stm32_adc_start_conv() - Start conversions for regular channels.
* @adc: stm32 adc instance
@@ -870,11 +887,37 @@ static irqreturn_t stm32_adc_trigger_handler(int irq, void *p)
{},
};
+static int stm32_adc_of_get_resolution(struct iio_dev *indio_dev)
+{
+ struct device_node *node = indio_dev->dev.of_node;
+ struct stm32_adc *adc = iio_priv(indio_dev);
+ unsigned int i;
+ u32 res;
+
+ if (of_property_read_u32(node, "assigned-resolution-bits", &res))
+ res = stm32f4_adc_resolutions[0];
+
+ for (i = 0; i < ARRAY_SIZE(stm32f4_adc_resolutions); i++)
+ if (res == stm32f4_adc_resolutions[i])
+ break;
+ if (i >= ARRAY_SIZE(stm32f4_adc_resolutions)) {
+ dev_err(&indio_dev->dev, "Bad resolution: %u bits\n", res);
+ return -EINVAL;
+ }
+
+ dev_dbg(&indio_dev->dev, "Using %u bits resolution\n", res);
+ adc->res = i;
+
+ return 0;
+}
+
static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
struct iio_chan_spec *chan,
const struct stm32_adc_chan_spec *channel,
int scan_index)
{
+ struct stm32_adc *adc = iio_priv(indio_dev);
+
chan->type = channel->type;
chan->channel = channel->channel;
chan->datasheet_name = channel->name;
@@ -883,7 +926,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
chan->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
chan->scan_type.sign = 'u';
- chan->scan_type.realbits = 12;
+ chan->scan_type.realbits = stm32f4_adc_resolutions[adc->res];
chan->scan_type.storagebits = 16;
chan->ext_info = stm32_adc_ext_info;
}
@@ -1022,6 +1065,11 @@ static int stm32_adc_probe(struct platform_device *pdev)
return ret;
}
+ ret = stm32_adc_of_get_resolution(indio_dev);
+ if (ret < 0)
+ goto err_clk_disable;
+ stm32_adc_set_res(adc);
+
ret = stm32_adc_chan_of_init(indio_dev);
if (ret < 0)
goto err_clk_disable;
--
1.9.1
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