ACPI / PMIC: Stop xpower OPRegion handler relying on IIO

The intel_pmic_xpower code provides an OPRegion handler, which must be
available before other drivers using it are loaded, which can only be
ensured if both the mfd and opregion drivers are built in, which is why
the Kconfig option for intel_pmic_xpower is a bool.

The use of IIO is causing trouble for generic distro configs here as
distros will typically want to build IIO drivers as modules and there
really is no reason to use IIO here. The reading of the ADC value is a
single regmap_bulk_read, which is already protected against races by
the regmap-lock.

This commit removes the use of IIO, allowing distros to enable the
driver without needing to built IIO in and also actually simplifies
the code.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/Kconfig

@@ -506,7 +506,7 @@ config CRC_PMIC_OPREGION
 
 config XPOWER_PMIC_OPREGION
 	bool "ACPI operation region support for XPower AXP288 PMIC"
-	depends on AXP288_ADC = y
+	depends on MFD_AXP20X_I2C
 	help
 	  This config adds ACPI operation region support for XPower AXP288 PMIC.
 

drivers/acpi/pmic/intel_pmic_xpower.c

@@ -18,7 +18,6 @@
 #include <linux/mfd/axp20x.h>
 #include <linux/regmap.h>
 #include <linux/platform_device.h>
-#include <linux/iio/consumer.h>
 #include "intel_pmic.h"
 
 #define XPOWER_GPADC_LOW	0x5b
@@ -186,28 +185,16 @@ static int intel_xpower_pmic_update_power(struct regmap *regmap, int reg,
  * @regmap: regmap of the PMIC device
  * @reg: register to get the reading
  *
- * We could get the sensor value by manipulating the HW regs here, but since
- * the axp288 IIO driver may also access the same regs at the same time, the
- * APIs provided by IIO subsystem are used here instead to avoid problems. As
- * a result, the two passed in params are of no actual use.
- *
  * Return a positive value on success, errno on failure.
  */
 static int intel_xpower_pmic_get_raw_temp(struct regmap *regmap, int reg)
 {
-	struct iio_channel *gpadc_chan;
-	int ret, val;
-
-	gpadc_chan = iio_channel_get(NULL, "axp288-system-temp");
-	if (IS_ERR_OR_NULL(gpadc_chan))
-		return -EACCES;
+	u8 buf[2];
 
-	ret = iio_read_channel_raw(gpadc_chan, &val);
-	if (ret < 0)
-		val = ret;
+	if (regmap_bulk_read(regmap, AXP288_GP_ADC_H, buf, 2))
+		return -EIO;
 
-	iio_channel_release(gpadc_chan);
-	return val;
+	return (buf[0] << 4) + ((buf[1] >> 4) & 0x0F);
 }
 
 static struct intel_pmic_opregion_data intel_xpower_pmic_opregion_data = {