commit 29005fafeab8d2a15091f8b7628fe08ef4aab868
author Abhijeet Dharmapurikar <adharmap@codeaurora.org> Mon Jul 15 17:57:27 2013 -0700
committer Abhijeet Dharmapurikar <adharmap@codeaurora.org> Mon Jul 15 20:31:56 2013 -0700
tree e8294a1cb63e21f3b827c837ce297867b3ee0150
parent 3c0cccf93df4855ebab815e133e8542d7a574b0c

hwmon: qpnp-current: fix converting offset and gain to voltage

The current driver forces a value of 0uV for offset and always
lands up with 17.857mV for gain. The raw values for offset and
gain are correct however.

Update the driver to do a proper conversion of raw offset and
gain to values in microvolts.

Change-Id: I19eda7a4f0cc8ab6af0d31e01e1168d99f00bf7a
Signed-off-by: Abhijeet Dharmapurikar <adharmap@codeaurora.org>

drivers/hwmon/qpnp-adc-current.c

diff --git a/drivers/hwmon/qpnp-adc-current.c b/drivers/hwmon/qpnp-adc-current.c
index 27818b4..94fad74 100644
--- a/drivers/hwmon/qpnp-adc-current.c
+++ b/drivers/hwmon/qpnp-adc-current.c
@@ -499,10 +499,13 @@
 	return 0;
 }
 
+#define IADC_CENTER	0xC000
+#define IADC_READING_RESOLUTION_N	542535
+#define IADC_READING_RESOLUTION_D	100000
 static int32_t qpnp_convert_raw_offset_voltage(void)
 {
 	struct qpnp_iadc_drv *iadc = qpnp_iadc;
-	uint32_t num = 0;
+	s64 numerator;
 
 	if ((iadc->adc->calib.gain_raw - iadc->adc->calib.offset_raw) == 0) {
 		pr_err("raw offset errors! raw_gain:0x%x and raw_offset:0x%x\n",
@@ -510,12 +513,16 @@
 		return -EINVAL;
 	}
 
-	iadc->adc->calib.offset_uv = 0;
+	numerator = iadc->adc->calib.offset_raw - IADC_CENTER;
+	numerator *= IADC_READING_RESOLUTION_N;
+	iadc->adc->calib.offset_uv = div_s64(numerator,
+						IADC_READING_RESOLUTION_D);
 
-	num = iadc->adc->calib.gain_raw - iadc->adc->calib.offset_raw;
+	numerator = iadc->adc->calib.gain_raw - iadc->adc->calib.offset_raw;
+	numerator *= IADC_READING_RESOLUTION_N;
 
-	iadc->adc->calib.gain_uv = (num * QPNP_ADC_GAIN_NV)/
-		(iadc->adc->calib.gain_raw - iadc->adc->calib.offset_raw);
+	iadc->adc->calib.gain_uv = div_s64(numerator,
+						IADC_READING_RESOLUTION_D);
 
 	pr_debug("gain_uv:%d offset_uv:%d\n",
 			iadc->adc->calib.gain_uv, iadc->adc->calib.offset_uv);