On Fri, Jan 23, 2015 at 11:49 PM, Caesar Wang <wxt at rock-chips.com> 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 at rock-chips.com>
> Reviewed-by: Dmitry Torokhov <dmitry.torokhov at 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 at 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;
I don't think you need this check since this is v2_code_table[0].
But, it doesn't hurt, so either way, this is:
Reviewed-by: Daniel Kurtz <djkurtz at chromium.org>
> 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
>
>
