Re: [PATCH 7/9] net: ethernet: ti: cpts: calc mult and shift from refclk freq

[Grygorii Strashko]

On 09/15/2016 12:03 AM, Richard Cochran wrote:
> On Wed, Sep 14, 2016 at 11:47:46PM +0300, Grygorii Strashko wrote:
> > As I understand (and tested), clocks_calc_mult_shift() will
> > return max possible mult which can be used without overflow.
>
> Yes, BUT the returned values depends on the @maxsec input.  As the
> kerneldec says,
>
>  * Larger ranges may reduce the conversion accuracy by chosing smaller
>  * mult and shift factors.
>
> In addition to that, frequency tuning by calculating a percentage of
> 'mult', and if 'mult' is small, then the tuning resolution is poor.
>
> So we don't want @maxsec as large as possible, but as small as
> possible.

Ok. So, will it work if maxsec will be ~= (maxsec / 2) + 1?
+ 1 to cover potential delays of overflow check work execution.

[...]


--
regards,
-grygorii