iio: adc: stm32: add dt option to set resolution

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@st.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 9b49a6a..c28e7ff 100644 (file)
--- 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 @@ static const struct stm32_adc_chan_spec stm32f4_adc123_channels[] = {
        { 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 const struct iio_chan_spec_ext_info stm32_adc_ext_info[] = {
        {},
 };
 
+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;