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>

1 files changed, 70 insertions, 4 deletions

diff --git a/drivers/iio/adc/at91_adc.c b/drivers/iio/adc/at91_adc.c
index 6fc43c15f028..3fb3fe48a98c 100644
--- 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);