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[PATCH v2 4/5] thermal: rockchip: optimize the conversion table

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  [PATCH v2 4/5] thermal: rockchip: optimize the conversion table Caesar Wang <wxt@rock-chips.com> - 2016-11-23 15:40 +0100

#1528450 — [PATCH v2 4/5] thermal: rockchip: optimize the conversion table

In order to support the valid temperature can conver to analog value.
The rockchip thermal driver has not supported the all valid temperature
to convert the analog value. (e.g.: 61C, 62C, 63C....)

For example:
In some cases, we need adjust the trip point.
$cd /sys/class/thermal/thermal_zone*
$echo 68000 > trip_point_0_temp
That will return the max analogic value indicates the invalid before
posting this patch.

So, this patch will optimize the conversion table to support the other
cases.

Signed-off-by: Caesar Wang <wxt@rock-chips.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
---

Changes in v2:
- improve the commit as Brian commnets on https://patchwork.kernel.org/patch/9440985

Changes in v1: None

 drivers/thermal/rockchip_thermal.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c
index e243e40..0d50df7 100644
--- a/drivers/thermal/rockchip_thermal.c
+++ b/drivers/thermal/rockchip_thermal.c
@@ -401,6 +401,8 @@ static u32 rk_tsadcv2_temp_to_code(const struct chip_tsadc_table *table,
 				   int temp)
 {
 	int high, low, mid;
+	unsigned long num;
+	unsigned int denom;
 	u32 error = table->data_mask;
 
 	low = 0;
@@ -421,6 +423,27 @@ static u32 rk_tsadcv2_temp_to_code(const struct chip_tsadc_table *table,
 		mid = (low + high) / 2;
 	}
 
+	/*
+	 * The conversion code granularity provided by the table. Let's
+	 * assume that the relationship between temperature and
+	 * analog value between 2 table entries is linear and interpolate
+	 * to produce less granular result.
+	 */
+	num = abs(table->id[mid].code - table->id[mid + 1].code);
+	num *= temp - table->id[mid].temp;
+	denom = table->id[mid + 1].temp - table->id[mid].temp;
+
+	switch (table->mode) {
+	case ADC_DECREMENT:
+		return table->id[mid].code - (num / denom);
+	case ADC_INCREMENT:
+		return table->id[mid].code + (num / denom);
+	default:
+		pr_err("%s: invalid conversion table, mode=%d\n",
+		       __func__, table->mode);
+		return error;
+	}
+
 exit:
 	pr_err("%s: invalid temperature, temp=%d error=%d\n",
 	       __func__, temp, error);
-- 
2.7.4

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