[PATCH v2] clk: fix clk_get_rate() documentation

[Heinrich Schuchardt]

On 2/14/21 4:49 AM, Jesse T wrote:
> Awesome, thanks! I must have forgotten how twos complement works for a
> sec...
>
> On Sat, Feb 13, 2021 at 10:17 PM Giulio Benetti <
> giulio.benetti at benettiengineering.com> wrote:
>
>> Hi Jesse,
>>
>> Il giorno 14 feb 2021, alle ore 03:58, Jesse T <mr.bossman075 at gmail.com>
>> ha scritto:
>>
>> 
>> This looks good to me, and helps beginners like me. As for the function
>> itself, i have 2 concerns: If it does return a negative value why is it
>> unsigned, if it is in fact signed that a clock above 2.2Ghz is a negative
>> number.
>>
>>
>> I was worried too at first sight but if you try to check negative numbers
>> you see that -1 is 0xFFFFFFFF so in the worst case you only loose 4095
>> numbers from the maximum, try to check with hex calculator. And that is the
>> trick.
>>
>> As for the IS_ERR_VALUE macro there still is a chance that it will error
>> if the clock just so happens to be 2^31  through 2^31 + number of err
>> values.
>>
>>
>> This is answered from above and IS_ERR_VALUE is a very contracted macro
>> that basically let you to keep value NOT valid if (0 > value > 4095).
>>
>> Just voicing my concerns i assume as i learn more about uboot,
>> linux,rtos's and different programs there will be minor issues like this.
>>
>>
>> Sure, no problem :-)
>>
>> Giulio
>>
>>
>> On Sat, Feb 13, 2021 at 9:17 PM Giulio Benetti <
>> giulio.benetti at benettiengineering.com> wrote:
>>
>>> Improve clk_get_rate() @return documentation that otherwise is a bit
>>> ambiguous. At the moment I expect to return 0 as error since the return
>>> type is 'ulong', instead the function really returns negative value in
>>> case the corresponding function pointer is null and returns 0 if the clock
>>> is invalid.
>>>
>>> Signed-off-by: Giulio Benetti <giulio.benetti at benettiengineering.com>
>>> ---
>>> V1->V2:
>>> * previous comment was wrong, this function returns negative value, so
>>> let's
>>>    improve it's @return documentation as suggested by Simon Glass
>>> ---
>>>   include/clk.h | 3 ++-
>>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/include/clk.h b/include/clk.h
>>> index ca6b85fa6f..5a8c7244d0 100644
>>> --- a/include/clk.h
>>> +++ b/include/clk.h
>>> @@ -344,7 +344,8 @@ int clk_free(struct clk *clk);
>>>    *
>>>    * @clk:       A clock struct that was previously successfully requested
>>> by
>>>    *             clk_request/get_by_*().
>>> - * @return clock rate in Hz, or -ve error code.
>>> + * @return clock rate in Hz on success, 0 for invalid clock, or -ve
>>> error code
>>> + *        for other errors.
>>>    */
>>>   ulong clk_get_rate(struct clk *clk);
>>>
>>> --
>>> 2.25.1
>>>
>>>

Cc: Lukasz Majewski <lukma at denx.de>
Lukasz is maintainer for CLOCK.