[PATCH v5] thermal: rockchip: make temperature reporting much more accurate
From: Caesar Wang <hidden>
Date: 2015-01-23 15:50:22
Also in:
linux-pm, lkml
Subsystem:
arm/rockchip soc support, the rest, thermal · Maintainers:
Heiko Stuebner, Linus Torvalds, Rafael J. Wysocki, Daniel Lezcano
In general, the kernel should report temperature readings exactly as
reported by the hardware. The cpu / gpu thermal driver works in 5 degree
increments,but we ought to do more accurate. The temperature will do
linear interpolation between the entries in the table.
Test= $md5sum /dev/zero &
$while true; do grep "" /sys/class/thermal/thermal_zone[1-2]/temp;
sleep .5; done
e.g. We can get the result as follows:
/sys/class/thermal/thermal_zone1/temp:39994
/sys/class/thermal/thermal_zone2/temp:39086
/sys/class/thermal/thermal_zone1/temp:39994
/sys/class/thermal/thermal_zone2/temp:39540
/sys/class/thermal/thermal_zone1/temp:39540
/sys/class/thermal/thermal_zone2/temp:39540
/sys/class/thermal/thermal_zone1/temp:39540
/sys/class/thermal/thermal_zone2/temp:39994
Signed-off-by: Caesar Wang <redacted>
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
Changes in v5:
Fixed some style.
Changes in v4:
"return -EAGAIN" instead of "return rk_tsadcv2_code_to_temp(code)"
Changes in v3:
Suggested-by Daniel Kurtz,
the check doesn't reject "code == 0xfff"
Fixed in rk_tsadcv2_code_to_temp(u32 code)
Changes in v2:
Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
drivers/thermal/rockchip_thermal.c | 38 +++++++++++++++++++++++++-------------
1 file changed, 25 insertions(+), 13 deletions(-)
diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c
index 1bcddfc..83bdf82 100644
--- a/drivers/thermal/rockchip_thermal.c
+++ b/drivers/thermal/rockchip_thermal.c@@ -193,19 +193,22 @@ static u32 rk_tsadcv2_temp_to_code(long temp) static long rk_tsadcv2_code_to_temp(u32 code) { - int high, low, mid; - - low = 0; - high = ARRAY_SIZE(v2_code_table) - 1; - mid = (high + low) / 2; - - if (code > v2_code_table[low].code || code < v2_code_table[high].code) - return 125000; /* No code available, return max temperature */ + unsigned int low = 0; + unsigned int high = ARRAY_SIZE(v2_code_table) - 1; + unsigned int mid = (low + high) / 2; + unsigned int num; + unsigned long denom; + + /* Invalid code, return -EAGAIN */ + if (code > TSADCV2_DATA_MASK) + return -EAGAIN; - while (low <= high) { - if (code >= v2_code_table[mid].code && code < - v2_code_table[mid - 1].code) - return v2_code_table[mid].temp; + while (low <= high && mid) { + if (code >= v2_code_table[mid].code && + code < v2_code_table[mid - 1].code) + break; + else if (code == TSADCV2_DATA_MASK) + break; else if (code < v2_code_table[mid].code) low = mid + 1; else
@@ -213,7 +216,16 @@ static long rk_tsadcv2_code_to_temp(u32 code) mid = (low + high) / 2; } - return 125000; + /* + * The 5C granularity provided by the table is too much. Let's + * assume that the relationship between sensor readings and + * temperature between 2 table entries is linear and interpolate + * to produce less granular result. + */ + num = v2_code_table[mid].temp - v2_code_table[mid - 1].temp; + num *= v2_code_table[mid - 1].code - code; + denom = v2_code_table[mid - 1].code - v2_code_table[mid].code; + return v2_code_table[mid - 1].temp + (num / denom); } /**
--
1.9.1