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SubjectRe: [PATCH v1] thermal: rockchip: make temperature reporting much more accurate
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 <wxt@rock-chips.com>

I did several review this patch on the Chrome OS gerrit, so

Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

>
> ---
>
> 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


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