[PATCH 2/3] iio: ad5064: Explicitly configure whether to use external supply

[Paul Cercueil <paul.cercueil-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>]

Previously the driver would revert to internal supply if the
external supply couldn't be found. This had multiple problems:
- it caused silently ignored errors when a regulator was intended
  to be supplied, but was not specified correctly.
- if CONFIG_REGULATOR is disabled, regulator_get() will always
  return a dummy regulator, which caused a device to always use
  the external vref mode, even though there is none.

This patch addresses the issue by adding a platform data structure,
containing a boolean field use_external_ref. If the platform data
structure is present and if that boolean is set, the external vref
is used; otherwise the internal vref is used.

In the case where devicetree is used, and if regulators are listed
as external references in the device tree, we assume that the
external reference should be used.

In the case where an external vref is wanted but regulator_get()
fails, the driver no longer reverts to using the internal vref,
but returns an error instead.

Signed-off-by: Paul Cercueil <paul.cercueil-OyLXuOCK7orQT0dZR+AlfA@public.gmane.org>
---
 drivers/iio/dac/ad5064.c             | 36 +++++++++++++++++++++++++++---------
 include/linux/platform_data/ad5064.h | 21 +++++++++++++++++++++
 2 files changed, 48 insertions(+), 9 deletions(-)
 create mode 100644 include/linux/platform_data/ad5064.h

diff --git a/drivers/iio/dac/ad5064.c b/drivers/iio/dac/ad5064.c
index c067e68..7146f42 100644
--- a/drivers/iio/dac/ad5064.c
+++ b/drivers/iio/dac/ad5064.c
@@ -2,7 +2,7 @@
  * AD5024, AD5025, AD5044, AD5045, AD5064, AD5064-1, AD5065, AD5628, AD5629R,
  * AD5648, AD5666, AD5668, AD5669R Digital to analog converters driver
  *
- * Copyright 2011 Analog Devices Inc.
+ * Copyright 2011, 2015 Analog Devices Inc.
  *
  * Licensed under the GPL-2.
  */
@@ -21,6 +21,8 @@
 #include <linux/iio/iio.h>
 #include <linux/iio/sysfs.h>
 
+#include <linux/platform_data/ad5064.h>
+
 #define AD5064_MAX_DAC_CHANNELS			8
 #define AD5064_MAX_VREFS			4
 
@@ -446,6 +448,7 @@ static int ad5064_probe(struct device *dev, enum ad5064_type type,
 	unsigned int midscale;
 	unsigned int i;
 	int ret;
+	bool ext_vref;
 
 	indio_dev = devm_iio_device_alloc(dev, sizeof(*st));
 	if (indio_dev == NULL)
@@ -461,11 +464,30 @@ static int ad5064_probe(struct device *dev, enum ad5064_type type,
 	for (i = 0; i < ad5064_num_vref(st); ++i)
 		st->vref_reg[i].supply = ad5064_vref_name(st, i);
 
-	ret = devm_regulator_bulk_get(dev, ad5064_num_vref(st),
-		st->vref_reg);
-	if (ret) {
-		if (!st->chip_info->internal_vref)
+	if (dev->of_node) {
+		for (i = 0; ext_vref && i < ad5064_num_vref(st); ++i)
+			ext_vref = of_property_read_bool(dev->of_node,
+					ad5064_vref_name(st, i));
+	} else {
+		struct ad5064_platform_data *pdata = dev->platform_data;
+
+		ext_vref = pdata && pdata->use_external_ref;
+	}
+
+	if (ext_vref) {
+		ret = devm_regulator_bulk_get(dev, ad5064_num_vref(st),
+					st->vref_reg);
+		if (ret)
 			return ret;
+		ret = regulator_bulk_enable(ad5064_num_vref(st), st->vref_reg);
+		if (ret)
+			return ret;
+	} else {
+		if (!st->chip_info->internal_vref) {
+			dev_err(dev, "No vref available\n");
+			return -ENXIO;
+		}
+
 		st->use_internal_vref = true;
 		ret = ad5064_write(st, AD5064_CMD_CONFIG, 0,
 			AD5064_CONFIG_INT_VREF_ENABLE, 0);
@@ -474,10 +496,6 @@ static int ad5064_probe(struct device *dev, enum ad5064_type type,
 				ret);
 			return ret;
 		}
-	} else {
-		ret = regulator_bulk_enable(ad5064_num_vref(st), st->vref_reg);
-		if (ret)
-			return ret;
 	}
 
 	indio_dev->dev.parent = dev;
diff --git a/include/linux/platform_data/ad5064.h b/include/linux/platform_data/ad5064.h
new file mode 100644
index 0000000..69bb5fe
--- /dev/null
+++ b/include/linux/platform_data/ad5064.h
@@ -0,0 +1,21 @@
+/*
+ * Analog Devices AD5064 DAC driver
+ *
+ * Copyright 2015 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2.
+ */
+
+#ifndef __IIO_ADC_AD5064_H__
+#define __IIO_ADC_AD5064_H__
+
+/**
+ * struct ad5064_platform_data - AD5064 platform data
+ * @use_external_ref: If set to true use an external voltage reference connected
+ * to the VREF pin, otherwise use the internal reference derived from Vdd.
+ */
+struct ad5064_platform_data {
+	bool use_external_ref;
+};
+
+#endif
-- 
2.5.3