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    Subject[PATCH 21/57] power: Overflow in current calculation
    Date
    From: Paer-Olof Haakansson <par-olof.hakansson@stericsson.com>

    When calculating the average current the nominator will
    overflow when the charging current is high.

    Signed-off-by: Henrik Sölver <henrik.solver@stericsson.com>
    Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
    Reviewed-by: Par-Olof HAKANSSON <par-olof.hakansson@stericsson.com>
    Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>
    ---
    drivers/power/ab8500_fg.c | 15 ++++++++-------
    1 files changed, 8 insertions(+), 7 deletions(-)

    diff --git a/drivers/power/ab8500_fg.c b/drivers/power/ab8500_fg.c
    index 46010ec..7c42150 100644
    --- a/drivers/power/ab8500_fg.c
    +++ b/drivers/power/ab8500_fg.c
    @@ -805,15 +805,13 @@ static void ab8500_fg_acc_cur_work(struct work_struct *work)

    /*
    * Convert to unit value in mA
    - * Full scale input voltage is
    - * 66.660mV => LSB = 66.660mV/(4096*res) = 1.627mA
    - * Given a 250ms conversion cycle time the LSB corresponds
    - * to 112.9 nAh. Convert to current by dividing by the conversion
    + * by dividing by the conversion
    * time in hours (= samples / (3600 * 4)h)
    - * 112.9nAh assumes 10mOhm, but fg_res is in 0.1mOhm
    + * and multiply with 1000
    */
    - di->avg_curr = (val * QLSB_NANO_AMP_HOURS_X10 * 36) /
    - (1000 * di->bat->fg_res * (di->fg_samples / 4));
    +
    + di->avg_curr = (di->accu_charge * 36) /
    + ((di->fg_samples / 4) * 10);

    di->flags.conv_done = true;

    @@ -821,6 +819,9 @@ static void ab8500_fg_acc_cur_work(struct work_struct *work)

    queue_work(di->fg_wq, &di->fg_work);

    + dev_dbg(di->dev,
    + "fg_res: %d, fg_samples: %d, gasg: %d, accu_charge: %d\n",
    + di->bat->fg_res, di->fg_samples, val, di->accu_charge);
    return;
    exit:
    dev_err(di->dev,
    --
    1.7.5.4
    --
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