iio: adc: ti-ads7950: Allow to use on ACPI platforms

ACPI enabled platforms do not have a mean of regulators. Instead we use
hard coded voltage value for reference pin. When value is 0 (default) we
fall back to request a regulator.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/ti-ads7950.c b/drivers/iio/adc/ti-ads7950.c
index 26b980a1604b926c7cec7bfcb42126e7213f2036..a376190914ad19f9b5e493642cbf52c64bef79a8 100644 (file)
--- a/drivers/iio/adc/ti-ads7950.c
+++ b/drivers/iio/adc/ti-ads7950.c
@@ -21,6 +21,7 @@
  * GNU General Public License for more details.
  */
 
+#include <linux/acpi.h>
 #include <linux/bitops.h>
 #include <linux/device.h>
 #include <linux/err.h>
@@ -37,6 +38,12 @@
 #include <linux/iio/trigger_consumer.h>
 #include <linux/iio/triggered_buffer.h>
 
+/*
+ * In case of ACPI, we use the 5000 mV as default for the reference pin.
+ * Device tree users encode that via the vref-supply regulator.
+ */
+#define TI_ADS7950_VA_MV_ACPI_DEFAULT  5000
+
 #define TI_ADS7950_CR_MANUAL   BIT(12)
 #define TI_ADS7950_CR_WRITE    BIT(11)
 #define TI_ADS7950_CR_CHAN(ch) ((ch) << 7)
@@ -58,6 +65,7 @@ struct ti_ads7950_state {
        struct spi_message      scan_single_msg;
 
        struct regulator        *reg;
+       unsigned int            vref_mv;
 
        unsigned int            settings;
 
@@ -305,11 +313,15 @@ static int ti_ads7950_get_range(struct ti_ads7950_state *st)
 {
        int vref;
 
-       vref = regulator_get_voltage(st->reg);
-       if (vref < 0)
-               return vref;
+       if (st->vref_mv) {
+               vref = st->vref_mv;
+       } else {
+               vref = regulator_get_voltage(st->reg);
+               if (vref < 0)
+                       return vref;
 
-       vref /= 1000;
+               vref /= 1000;
+       }
 
        if (st->settings & TI_ADS7950_CR_RANGE_5V)
                vref *= 2;
@@ -411,6 +423,10 @@ static int ti_ads7950_probe(struct spi_device *spi)
        spi_message_init_with_transfers(&st->scan_single_msg,
                                        st->scan_single_xfer, 3);
 
+       /* Use hard coded value for reference voltage in ACPI case */
+       if (ACPI_COMPANION(&spi->dev))
+               st->vref_mv = TI_ADS7950_VA_MV_ACPI_DEFAULT;
+
        st->reg = devm_regulator_get(&spi->dev, "vref");
        if (IS_ERR(st->reg)) {
                dev_err(&spi->dev, "Failed get get regulator \"vref\"\n");