[PATCH v2] adc: rockchip-saradc: add support for getting reference voltage value

[Peter Cai]

Mirroring commit 97ab802aa36f ("adc: meson-saradc: add support for
getting reference voltage value") for meson-saradc, this adds support
for getting the "vref-supply" regulator and register it as the ADC's
reference voltage regulator, so clients can translate sampled ADC values
to voltage.

Signed-off-by: Peter Cai <peter at typeblog.net>
Reviewed-by: John Keeping <john at metanate.com>
Tested-by: John Keeping <john at metanate.com>
Cc: Simon Glass <sjg at chromium.org>
Cc: Philipp Tomsich <philipp.tomsich at vrull.eu>
Cc: Kever Yang <kever.yang at rock-chips.com>
---
Changes in v2:
- Reordered local variables in `rockchip_saradc_probe`.
---
 drivers/adc/rockchip-saradc.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/adc/rockchip-saradc.c b/drivers/adc/rockchip-saradc.c
index e464d33f2267..4007188133c8 100644
--- a/drivers/adc/rockchip-saradc.c
+++ b/drivers/adc/rockchip-saradc.c
@@ -13,6 +13,7 @@
 #include <asm/io.h>
 #include <linux/bitops.h>
 #include <linux/err.h>
+#include <power/regulator.h>
 
 #define SARADC_CTRL_CHN_MASK		GENMASK(2, 0)
 #define SARADC_CTRL_POWER_CTRL		BIT(3)
@@ -100,8 +101,11 @@ int rockchip_saradc_stop(struct udevice *dev)
 
 int rockchip_saradc_probe(struct udevice *dev)
 {
+	struct adc_uclass_plat *uc_pdata = dev_get_uclass_plat(dev);
 	struct rockchip_saradc_priv *priv = dev_get_priv(dev);
+	struct udevice *vref;
 	struct clk clk;
+	int vref_uv;
 	int ret;
 
 	ret = clk_get_by_index(dev, 0, &clk);
@@ -114,6 +118,23 @@ int rockchip_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;
 }
 
-- 
2.35.1