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    Subject[PATCH 04/13] thermal/drivers/hisi: Simplify the temperature/step computation
    Date
    The step and the base temperature are fixed values, we can simplify the
    computation by converting the base temperature to milli celsius and use a
    pre-computed step value. That saves us a lot of mult + div for nothing at
    runtime.

    Take also the opportunity to change the function names to be consistent with
    the rest of the code.

    Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
    ---
    drivers/thermal/hisi_thermal.c | 41 ++++++++++++++++++++++++++++-------------
    1 file changed, 28 insertions(+), 13 deletions(-)

    diff --git a/drivers/thermal/hisi_thermal.c b/drivers/thermal/hisi_thermal.c
    index 67db523..b58ad40 100644
    --- a/drivers/thermal/hisi_thermal.c
    +++ b/drivers/thermal/hisi_thermal.c
    @@ -35,8 +35,9 @@
    #define TEMP0_RST_MSK (0x1C)
    #define TEMP0_VALUE (0x28)

    -#define HISI_TEMP_BASE (-60)
    +#define HISI_TEMP_BASE (-60000)
    #define HISI_TEMP_RESET (100000)
    +#define HISI_TEMP_STEP (784)

    #define HISI_MAX_SENSORS 4
    #define HISI_DEFAULT_SENSOR 2
    @@ -61,19 +62,32 @@ struct hisi_thermal_data {
    void __iomem *regs;
    };

    -/* in millicelsius */
    -static inline int _step_to_temp(int step)
    +/*
    + * The temperature computation on the tsensor is as follow:
    + * Unit: millidegree Celsius
    + * Step: 255/200 (0.7843)
    + * Temperature base: -60°C
    + *
    + * The register is programmed in temperature steps, every step is 784
    + * millidegree and begins at -60 000 m°C
    + *
    + * The temperature from the steps:
    + *
    + * Temp = TempBase + (steps x 784)
    + *
    + * and the steps from the temperature:
    + *
    + * steps = (Temp - TempBase) / 784
    + *
    + */
    +static inline int hisi_thermal_step_to_temp(int step)
    {
    - /*
    - * Every step equals (1 * 200) / 255 celsius, and finally
    - * need convert to millicelsius.
    - */
    - return (HISI_TEMP_BASE * 1000 + (step * 200000 / 255));
    + return HISI_TEMP_BASE + (step * HISI_TEMP_STEP);
    }

    -static inline long _temp_to_step(long temp)
    +static inline long hisi_thermal_temp_to_step(long temp)
    {
    - return ((temp - HISI_TEMP_BASE * 1000) * 255) / 200000;
    + return (temp - HISI_TEMP_BASE) / HISI_TEMP_STEP;
    }

    static long hisi_thermal_get_sensor_temp(struct hisi_thermal_data *data,
    @@ -99,7 +113,7 @@ static long hisi_thermal_get_sensor_temp(struct hisi_thermal_data *data,
    usleep_range(3000, 5000);

    val = readl(data->regs + TEMP0_VALUE);
    - val = _step_to_temp(val);
    + val = hisi_thermal_step_to_temp(val);

    mutex_unlock(&data->thermal_lock);

    @@ -126,10 +140,11 @@ static void hisi_thermal_enable_bind_irq_sensor
    writel((sensor->id << 12), data->regs + TEMP0_CFG);

    /* enable for interrupt */
    - writel(_temp_to_step(sensor->thres_temp) | 0x0FFFFFF00,
    + writel(hisi_thermal_temp_to_step(sensor->thres_temp) | 0x0FFFFFF00,
    data->regs + TEMP0_TH);

    - writel(_temp_to_step(HISI_TEMP_RESET), data->regs + TEMP0_RST_TH);
    + writel(hisi_thermal_temp_to_step(HISI_TEMP_RESET),
    + data->regs + TEMP0_RST_TH);

    /* enable module */
    writel(0x1, data->regs + TEMP0_RST_MSK);
    --
    2.7.4
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