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    SubjectRe: [PATCH 04/13] thermal/drivers/hisi: Simplify the temperature/step computation
    On Wed, Aug 30, 2017 at 10:47:28AM +0200, Daniel Lezcano wrote:
    > 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>

    Reviewed-by: Leo Yan <leo.yan@linaro.org>
    Tested-by: Leo Yan <leo.yan@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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