Re: [PATCH 04/13] thermal/drivers/hisi: Simplify the temperature/step computation

Leo Yan
2017-09-01T14:25:00Z

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
>