power_supply: fix up CHARGE_COUNTER output to be more precise

As Richard Smith pointed out, ACR * 6250 / 15 provides for less
precision loss than ACR * 4167 / 10, _and_ it doesn't overflow.  Switch
to using that equation for CHARGE_COUNTER.

Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: "Richard A. Smith" <richard@laptop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>

diff --git a/drivers/power/olpc_battery.c b/drivers/power/olpc_battery.c
index 9dd1589..32570af 100644 (file)
--- a/drivers/power/olpc_battery.c
+++ b/drivers/power/olpc_battery.c
@@ -19,7 +19,7 @@
 
 #define EC_BAT_VOLTAGE 0x10    /* uint16_t,    *9.76/32,    mV   */
 #define EC_BAT_CURRENT 0x11    /* int16_t,     *15.625/120, mA   */
-#define EC_BAT_ACR     0x12    /* int16_t,     *416.7,      µAh  */
+#define EC_BAT_ACR     0x12    /* int16_t,     *6250/15,    µAh  */
 #define EC_BAT_TEMP    0x13    /* uint16_t,    *100/256,   °C  */
 #define EC_AMB_TEMP    0x14    /* uint16_t,    *100/256,   °C  */
 #define EC_BAT_STATUS  0x15    /* uint8_t,     bitmask */
@@ -295,7 +295,7 @@ static int olpc_bat_get_property(struct power_supply *psy,
                        return ret;
 
                ec_word = be16_to_cpu(ec_word);
-               val->intval = ec_word * 4167 / 10;
+               val->intval = ec_word * 6250 / 15;
                break;
        case POWER_SUPPLY_PROP_SERIAL_NUMBER:
                ret = olpc_ec_cmd(EC_BAT_SERIAL, NULL, 0, (void *)&ser_buf, 8);