iio: at91_adc: add low and high res support

at91 adc offers the choice between two resolutions: low and high.
The low and high resolution values depends on adc IP version, as many IP
properties have been exposed through device tree, these settings have also
been added to the dt bindings.

Signed-off-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/Documentation/devicetree/bindings/arm/atmel-adc.txt b/Documentation/devicetree/bindings/arm/atmel-adc.txt
index c63097d6afebd06e7f95d4ad9c42a34e72b8054b..fd2d69ee2876bd958ccd88748d8717cf9fd8eb6b 100644 (file)
--- a/Documentation/devicetree/bindings/arm/atmel-adc.txt
+++ b/Documentation/devicetree/bindings/arm/atmel-adc.txt
@@ -14,9 +14,17 @@ Required properties:
   - atmel,adc-status-register: Offset of the Interrupt Status Register
   - atmel,adc-trigger-register: Offset of the Trigger Register
   - atmel,adc-vref: Reference voltage in millivolts for the conversions
+  - atmel,adc-res: List of resolution in bits supported by the ADC. List size
+                  must be two at least.
+  - atmel,adc-res-names: Contains one identifier string for each resolution
+                        in atmel,adc-res property. "lowres" and "highres"
+                        identifiers are required.
 
 Optional properties:
   - atmel,adc-use-external: Boolean to enable of external triggers
+  - atmel,adc-use-res: String corresponding to an identifier from
+                      atmel,adc-res-names property. If not specified, the highest
+                      resolution will be used.
  
 Optional trigger Nodes:
   - Required properties:
@@ -40,6 +48,9 @@ adc0: adc@fffb0000 {
        atmel,adc-trigger-register = <0x08>;
        atmel,adc-use-external;
        atmel,adc-vref = <3300>;
+       atmel,adc-res = <8 10>;
+       atmel,adc-res-names = "lowres", "highres";
+       atmel,adc-use-res = "lowres";
 
        trigger@0 {
                trigger-name = "external-rising";

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 6fc43c15f02878a295c80d9aab6fbcbbe00f98c1..3fb3fe48a98c7dc45dfaa2a4f91cf07276a8648c 100644 (file)
--- a/drivers/iio/adc/at91_adc.c
+++ b/drivers/iio/adc/at91_adc.c
@@ -57,6 +57,8 @@ struct at91_adc_state {
        u32                     trigger_number;
        bool                    use_external;
        u32                     vref_mv;
+       u32                     res;            /* resolution used for convertions */
+       bool                    low_res;        /* the resolution corresponds to the lowest one */
        wait_queue_head_t       wq_data_avail;
 };
 
@@ -138,7 +140,7 @@ static int at91_adc_channel_init(struct iio_dev *idev)
                chan->channel = bit;
                chan->scan_index = idx;
                chan->scan_type.sign = 'u';
-               chan->scan_type.realbits = 10;
+               chan->scan_type.realbits = st->res;
                chan->scan_type.storagebits = 16;
                chan->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE);
                chan->info_mask_separate = BIT(IIO_CHAN_INFO_RAW);
@@ -372,6 +374,59 @@ static int at91_adc_read_raw(struct iio_dev *idev,
        return -EINVAL;
 }
 
+static int at91_adc_of_get_resolution(struct at91_adc_state *st,
+                                     struct platform_device *pdev)
+{
+       struct iio_dev *idev = iio_priv_to_dev(st);
+       struct device_node *np = pdev->dev.of_node;
+       int count, i, ret = 0;
+       char *res_name, *s;
+       u32 *resolutions;
+
+       count = of_property_count_strings(np, "atmel,adc-res-names");
+       if (count < 2) {
+               dev_err(&idev->dev, "You must specified at least two resolution names for "
+                                   "adc-res-names property in the DT\n");
+               return count;
+       }
+
+       resolutions = kmalloc(count * sizeof(*resolutions), GFP_KERNEL);
+       if (!resolutions)
+               return -ENOMEM;
+
+       if (of_property_read_u32_array(np, "atmel,adc-res", resolutions, count)) {
+               dev_err(&idev->dev, "Missing adc-res property in the DT.\n");
+               ret = -ENODEV;
+               goto ret;
+       }
+
+       if (of_property_read_string(np, "atmel,adc-use-res", (const char **)&res_name))
+               res_name = "highres";
+
+       for (i = 0; i < count; i++) {
+               if (of_property_read_string_index(np, "atmel,adc-res-names", i, (const char **)&s))
+                       continue;
+
+               if (strcmp(res_name, s))
+                       continue;
+
+               st->res = resolutions[i];
+               if (!strcmp(res_name, "lowres"))
+                       st->low_res = true;
+               else
+                       st->low_res = false;
+
+               dev_info(&idev->dev, "Resolution used: %u bits\n", st->res);
+               goto ret;
+       }
+
+       dev_err(&idev->dev, "There is no resolution for %s\n", res_name);
+
+ret:
+       kfree(resolutions);
+       return ret;
+}
+
 static int at91_adc_probe_dt(struct at91_adc_state *st,
                             struct platform_device *pdev)
 {
@@ -415,6 +470,10 @@ static int at91_adc_probe_dt(struct at91_adc_state *st,
        }
        st->vref_mv = prop;
 
+       ret = at91_adc_of_get_resolution(st, pdev);
+       if (ret)
+               goto error_ret;
+
        st->registers = devm_kzalloc(&idev->dev,
                                     sizeof(struct at91_adc_reg_desc),
                                     GFP_KERNEL);
@@ -628,9 +687,16 @@ static int at91_adc_probe(struct platform_device *pdev)
         */
        ticks = round_up((st->startup_time * adc_clk /
                          1000000) - 1, 8) / 8;
-       at91_adc_writel(st, AT91_ADC_MR,
-                       (AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL) |
-                       (AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP));
+
+       if (st->low_res)
+               at91_adc_writel(st, AT91_ADC_MR,
+                               AT91_ADC_LOWRES |
+                               (AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL) |
+                               (AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP));
+       else
+               at91_adc_writel(st, AT91_ADC_MR,
+                               (AT91_ADC_PRESCAL_(prsc) & AT91_ADC_PRESCAL) |
+                               (AT91_ADC_STARTUP_(ticks) & AT91_ADC_STARTUP));
 
        /* Setup the ADC channels available on the board */
        ret = at91_adc_channel_init(idev);