# [PATCH 06/15] twl4030_charger: split uA calculation into a function.

From: NeilBrown
Date: Mon Feb 23 2015 - 23:36:12 EST

We will need this calculation in other places, so
create functions to map between register value and uA value.

Signed-off-by: NeilBrown <neilb@xxxxxxx>
---
drivers/power/twl4030_charger.c | 48 ++++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 13 deletions(-)

diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c
index db8931a17541..0b6fb06a0c01 100644
--- a/drivers/power/twl4030_charger.c
+++ b/drivers/power/twl4030_charger.c
@@ -178,6 +178,40 @@ static int twl4030_is_battery_present(struct twl4030_bci *bci)
}

/*
+ * TI provided formulas:
+ * CGAIN == 0: ICHG = (BCIICHG * 1.7) / (2^10 - 1) - 0.85
+ * CGAIN == 1: ICHG = (BCIICHG * 3.4) / (2^10 - 1) - 1.7
+ * Here we use integer approximation of:
+ * CGAIN == 0: val * 1.6618 - 0.85 * 1000
+ * CGAIN == 1: (val * 1.6618 - 0.85 * 1000) * 2
+ */
+/*
+ * convert twl register value for currents into uA
+ */
+static int regval2ua(int regval, bool cgain)
+{
+ if (cgain)
+ return (regval * 16618 - 8500 * 1000) / 5;
+ else
+ return (regval * 16618 - 8500 * 1000) / 10;
+}
+
+/*
+ * convert uA currents into twl register value
+ */
+static int ua2regval(int ua, bool cgain)
+{
+ int ret;
+ if (cgain)
+ ua /= 2;
+ ret = (ua * 10 + 8500 * 1000) / 16618;
+ /* rounding problems */
+ if (ret < 512)
+ ret = 512;
+ return ret;
+}
+
+/*
* Enable/Disable USB Charge functionality.
*/
static int twl4030_charger_enable_usb(struct twl4030_bci *bci, bool enable)
@@ -366,14 +400,6 @@ static int twl4030_bci_usb_ncb(struct notifier_block *nb, unsigned long val,
return NOTIFY_OK;
}

-/*
- * TI provided formulas:
- * CGAIN == 0: ICHG = (BCIICHG * 1.7) / (2^10 - 1) - 0.85
- * CGAIN == 1: ICHG = (BCIICHG * 3.4) / (2^10 - 1) - 1.7
- * Here we use integer approximation of:
- * CGAIN == 0: val * 1.6618 - 0.85
- * CGAIN == 1: (val * 1.6618 - 0.85) * 2
- */
static int twl4030_charger_get_current(void)
{
int curr;
@@ -388,11 +414,7 @@ static int twl4030_charger_get_current(void)
if (ret)
return ret;

- ret = (curr * 16618 - 850 * 10000) / 10;
- if (bcictl1 & TWL4030_CGAIN)
- ret *= 2;
-
- return ret;
+ return regval2ua(curr, bcictl1 & TWL4030_CGAIN);
}

/*

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