Messages in this thread | | | Date | Wed, 14 Sep 2016 23:03:32 +0200 | From | Richard Cochran <> | Subject | Re: [PATCH 7/9] net: ethernet: ti: cpts: calc mult and shift from refclk freq |
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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.
> if calculated results do not satisfy end user - the custom values can > be passed in DT.
If we calculate automatically, then the result had better well be optimal or nearly so. Otherwise, we should leave it as a manual input via DTS, IMHO, so that someone is forced to check the values.
Thanks, Richard
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