twl4030_charger: split uA calculation into a function.

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

Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: NeilBrown <neil@brown.name>
Signed-off-by: Sebastian Reichel <sre@kernel.org>

1 files changed, 35 insertions, 13 deletions

diff --git a/drivers/power/twl4030_charger.c b/drivers/power/twl4030_charger.c
index a075216d65ed..29984b263a35 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);
 }
 
 /*