[PATCH v6 3/5] adc: meson-saradc: add support for getting reference voltage value

[Marek Szyprowski]

Add support for getting the 'vref-supply' regulator and register it as
ADC's reference voltage regulator, so clients can translate sampled ADC
values to the voltage.

Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com>
Reviewed-by: Simon Glass <s...@chromium.org>
---
 drivers/adc/meson-saradc.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/adc/meson-saradc.c b/drivers/adc/meson-saradc.c
index 21db55831d..1a45a3a265 100644
--- a/drivers/adc/meson-saradc.c
+++ b/drivers/adc/meson-saradc.c
@@ -18,6 +18,7 @@
 #include <linux/delay.h>
 #include <linux/math64.h>
 #include <linux/bitfield.h>
+#include <power/regulator.h>
 
 #define MESON_SAR_ADC_REG0                                     0x00
        #define MESON_SAR_ADC_REG0_PANEL_DETECT                 BIT(31)
@@ -656,7 +657,10 @@ static int meson_saradc_stop(struct udevice *dev)
 
 static int meson_saradc_probe(struct udevice *dev)
 {
+       struct adc_uclass_plat *uc_pdata = dev_get_uclass_plat(dev);
        struct meson_saradc_priv *priv = dev_get_priv(dev);
+       struct udevice *vref;
+       int vref_uv;
        int ret;
 
        ret = regmap_init_mem(dev_ofnode(dev), &priv->regmap);
@@ -675,6 +679,23 @@ static int meson_saradc_probe(struct udevice *dev)
 
        priv->active_channel = -1;
 
+       ret = device_get_supply_regulator(dev, "vref-supply", &vref);
+       if (ret) {
+               printf("can't get vref-supply: %d\n", ret);
+               return ret;
+       }
+
+       vref_uv = regulator_get_value(vref);
+       if (vref_uv < 0) {
+               printf("can't get vref-supply value: %d\n", vref_uv);
+               return vref_uv;
+       }
+
+       /* VDD supplied by common vref pin */
+       uc_pdata->vdd_supply = vref;
+       uc_pdata->vdd_microvolts = vref_uv;
+       uc_pdata->vss_microvolts = 0;
+
        return 0;
 }
 
-- 
2.17.1