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

Daniel Lezcano
2017-08-30T08:48:57Z

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