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SubjectRe: Export clocks_calc_mult_shift() function
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On 03/14/2016 11:27 AM, Murali Karicheri wrote:
> On 03/08/2016 05:25 PM, Murali Karicheri wrote:
>> Hi,
>>
>> I found a patch posted sometime back to export the clocksource
>> function clocks_calc_mult_shift() so that it can be called by
>> drivers that are dynamically loadable. I have not seen any
>> comment against this. Wondering why this is not merged. We require
>> this function exported for use in our driver as well. Can you merge
>> the patch please. Or do you suggest me to repost the same?
>>
>> http://lkml.iu.edu/hypermail/linux/kernel/1502.2/01641.html
>>
>> Thanks
>>
> John,
>
> Some reason, your response didn't make into my inbox. So I am
> reproducing it below.
>
>> Why would the clocksource driver need to calculate the hz/shift value
>> instead of using the clocksource_register_hz/khz functions?
>>
>> thanks
>> -john
>
> John,
>
> In this use case, the timestamp for Tx/Rx is generated by a firmware
> that attach the timestamp raw count to the packet meta data when the
> same is received from the Packet Accelerator h/w at the ingress.
> We need to convert this raw count value to nano second and use a code
> like this.
>
> /* Convert a raw PA timer count to nanoseconds
> */
> static inline u64 tstamp_raw_to_ns(struct pa_core_device *core_dev, u32 lo,
> u32 hi)
> {
> u32 mult = core_dev->timestamp_info.mult;
> u32 shift = core_dev->timestamp_info.shift;
> u64 result;
>
> /* Minimize overflow errors by doing this in pieces */
> result = ((u64)lo * mult) >> shift;
> result += ((u64)hi << (32 - shift)) * mult;
>
> return result;
> }
>
> The mult, shift values are obtained using the existing clocks_calc_mult_shift()
> that will not work, if our driver is built as a dynamically loadable module
> as the symbol is not exported.
>
> Is there an alternative way of doing this without exporting this function.
> clocksource_register_hz/khz() can't help in this, right?
>
John,

I didn't see any response? Can I send a patch to export clocks_calc_mult_shift() function??

--
Murali Karicheri
Linux Kernel, Keystone

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