Subject: Re: [PATCH 1/6] thermal: brcmstb_thermal: Do not use DT coefficients

From: Florian Fainelli <[email-masked]>
Date: Wed, 4 Dec 2019 09:41:16 -0800

On 12/4/19 12:41 AM, Amit Kucheria wrote:
> On Wed, Oct 30, 2019 at 11:51 PM Florian Fainelli <[email-masked]> wrote:
>>
>> At the time the brcmstb_thermal driver and its binding were merged, the
>> DT binding did not make the coefficients properties a mandatory one,
>> therefore all users of the brcmstb_thermal driver out there have a non
>> functional implementation with zero coefficients. Even if these
>> properties were provided, the formula used for computation is incorrect.
>>
>> The coefficients are entirely process specific (right now, only 28nm is
>> supported) and not board or SoC specific, it is therefore appropriate to
>> hard code them in the driver given the compatibility string we are
>> probed with which has to be updated whenever a new process is
>> introduced.
>>
>> We remove the existing coefficients definition since subsequent patches
>> are going to add support for a new process and will introduce new
>> coefficients as well.
>>
>> Fixes: 9e03cf1b2dd5 ("thermal: add brcmstb AVS TMON driver")
> 
> I think you should fix the computation formula as the first patch and
> then merge the rest of this patch into your second patch.
> 
> I don't think the intermediate state of converting named constants to
> magic numbers is needed just to convert it over to another set of
> parameters.

ok, so you would rather see this patch using the defined constants while
fixing the formula, and in a subsequent patch getting rid of the
constant names since they are going to be added to a per-process table,
does that sound reasonable?

> 
> Regards,
> Amit
> 
>> Signed-off-by: Florian Fainelli <[email-masked]>
>> ---
>>  drivers/thermal/broadcom/brcmstb_thermal.c | 37 ++++------------------
>>  1 file changed, 6 insertions(+), 31 deletions(-)
>>
>> diff --git a/drivers/thermal/broadcom/brcmstb_thermal.c b/drivers/thermal/broadcom/brcmstb_thermal.c
>> index 5825ac581f56..42482af0422e 100644
>> --- a/drivers/thermal/broadcom/brcmstb_thermal.c
>> +++ b/drivers/thermal/broadcom/brcmstb_thermal.c
>> @@ -48,15 +48,6 @@
>>  #define AVS_TMON_TEMP_INT_CODE         0x1c
>>  #define AVS_TMON_TP_TEST_ENABLE                0x20
>>
>> -/* Default coefficients */
>> -#define AVS_TMON_TEMP_SLOPE            -487
>> -#define AVS_TMON_TEMP_OFFSET           410040
>> -
>> -/* HW related temperature constants */
>> -#define AVS_TMON_TEMP_MAX              0x3ff
>> -#define AVS_TMON_TEMP_MIN              -88161
>> -#define AVS_TMON_TEMP_MASK             AVS_TMON_TEMP_MAX
>> -
>>  enum avs_tmon_trip_type {
>>         TMON_TRIP_TYPE_LOW = 0,
>>         TMON_TRIP_TYPE_HIGH,
>> @@ -108,23 +99,11 @@ struct brcmstb_thermal_priv {
>>         struct thermal_zone_device *thermal;
>>  };
>>
>> -static void avs_tmon_get_coeffs(struct thermal_zone_device *tz, int *slope,
>> -                               int *offset)
>> -{
>> -       *slope = thermal_zone_get_slope(tz);
>> -       *offset = thermal_zone_get_offset(tz);
>> -}
>> -
>>  /* Convert a HW code to a temperature reading (millidegree celsius) */
>>  static inline int avs_tmon_code_to_temp(struct thermal_zone_device *tz,
>>                                         u32 code)
>>  {
>> -       const int val = code & AVS_TMON_TEMP_MASK;
>> -       int slope, offset;
>> -
>> -       avs_tmon_get_coeffs(tz, &slope, &offset);
>> -
>> -       return slope * val + offset;
>> +       return (410040 - (int)((code & 0x3FF) * 487));
>>  }
>>
>>  /*
>> @@ -136,20 +115,16 @@ static inline int avs_tmon_code_to_temp(struct thermal_zone_device *tz,
>>  static inline u32 avs_tmon_temp_to_code(struct thermal_zone_device *tz,
>>                                         int temp, bool low)
>>  {
>> -       int slope, offset;
>> -
>> -       if (temp < AVS_TMON_TEMP_MIN)
>> -               return AVS_TMON_TEMP_MAX; /* Maximum code value */
>> -
>> -       avs_tmon_get_coeffs(tz, &slope, &offset);
>> +       if (temp < -88161)
>> +               return 0x3FF;   /* Maximum code value */
>>
>> -       if (temp >= offset)
>> +       if (temp >= 410040)
>>                 return 0;       /* Minimum code value */
>>
>>         if (low)
>> -               return (u32)(DIV_ROUND_UP(offset - temp, abs(slope)));
>> +               return (u32)(DIV_ROUND_UP(410040 - temp, 487));
>>         else
>> -               return (u32)((offset - temp) / abs(slope));
>> +               return (u32)((410040 - temp) / 487);
>>  }
>>
>>  static int brcmstb_get_temp(void *data, int *temp)
>> --
>> 2.17.1
>>

-- 
Florian

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