[PATCH v3] thermal: rockchip: make temperature reporting much more accurate

From: sasukewxt@163•com (Caesar Wang)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v3] thermal: rockchip: make temperature reporting much more accurate
Date: Thu, 22 Jan 2015 12:57:08 +0800	[thread overview]
Message-ID: <54C08324.4050605@163.com> (raw)
In-Reply-To: <CAGS+omDdbUBn5swOZ23K3MpjzV3UMk3xABLWxj1SFE+s=FcHQA@mail.gmail.com>


? 2015?01?22? 12:25, Daniel Kurtz ??:
> On Thu, Jan 22, 2015 at 12:21 PM, Caesar Wang
> <caesar.wang@rock-chips•com> wrote:
>> ? 2015?01?22? 12:01, Daniel Kurtz ??:
>>
>>> On Thu, Jan 22, 2015 at 1:29 AM, Caesar Wang <wxt@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@rock-chips•com>
>>>> Reviewed-by: Dmitry Torokhov <dmitry.torokhov@gmail•com>
>>>>
>>>> ---
>>>>
>>>> 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 | 32
>>>> ++++++++++++++++++++++----------
>>>>    1 file changed, 22 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/drivers/thermal/rockchip_thermal.c
>>>> b/drivers/thermal/rockchip_thermal.c
>>>> index 1bcddfc..ce18007 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;
>>>> +       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;
>>>>
>>>> +       /* No code available, return callback */
>>>>           if (code > v2_code_table[low].code || code <
>>>> v2_code_table[high].code)
>>>> -               return 125000; /* No code available, return max
>>>> temperature */
>>>> +               return rk_tsadcv2_code_to_temp(code);
>>> Isn't this an infinite recursion?
>>
>> No, I think we can try check if it  is happened.
>> Maybe we can return a warning/error for it.
> I mean, if the 'if' condition is true, then this will just call the
> same function again with the same code, and again, and again...
> Just return an error code here, -ENOENT maybe?
> I am not sure what error code is appropriate.

Maybe "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;
>>>> +               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
>>>>
>>>>
>>>
>> --
>> Best regards
>> Caesar Wang (???)
>> ???????????
>> Fuzhou Rockchip Electronics Co.Ltd
>> ?????????????89????A?18??(350003)
>> Addr:No.18 Building, A District, No.89, software Boulevard Fuzhou,
>> Fujian,PRC
>> Email:wxt at rock-chips.com
>> Tel:+86-591-83991906/07->8221
>>
>>
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