[PATCH v1] thermal: rockchip: make temperature reporting much more accurate
From: dmitry.torokhov@gmail.com (Dmitry Torokhov)
Date: 2015-01-18 19:21:40
Also in:
linux-pm, lkml
On Mon, Jan 19, 2015 at 12:15:53AM +0800, Caesar Wang wrote:
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>I did several review this patch on the Chrome OS gerrit, so Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
quoted hunk ↗ jump to hunk
--- drivers/thermal/rockchip_thermal.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-)diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c index 1bcddfc..a7ae23a 100644 --- a/drivers/thermal/rockchip_thermal.c +++ b/drivers/thermal/rockchip_thermal.c@@ -193,19 +193,18 @@ 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; + unsigned int low = 0; + unsigned int high = ARRAY_SIZE(v2_code_table) - 1; + unsigned int mid = (low + high) / 2; + unsigned int scale; if (code > v2_code_table[low].code || code < v2_code_table[high].code) return 125000; /* No code available, return max temperature */ while (low <= high) { - if (code >= v2_code_table[mid].code && code < - v2_code_table[mid - 1].code) - return v2_code_table[mid].temp; + if (code >= v2_code_table[mid].code && + code < v2_code_table[mid - 1].code) + break; else if (code < v2_code_table[mid].code) low = mid + 1; else@@ -213,7 +212,16 @@ 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 extrapolate + * to produce less granular result. + */ + scale = (v2_code_table[mid].temp - v2_code_table[mid - 1].temp) / + (v2_code_table[mid - 1].code - v2_code_table[mid].code); + return v2_code_table[mid - 1].temp + + (v2_code_table[mid - 1].code - code) * scale; } /**-- 1.9.1
Thanks. -- Dmitry