Re: [RFC PATCH] clk: fractional-divider: Correct max_{m,n} handed over to rational_best_approximation()

[Andy Shevchenko]

+Cc: Mauro (below Q about sphinx and docs)

On Thu, Jul 15, 2021 at 11:14 AM Andy Shevchenko
<andy.shevchenko@xxxxxxxxx> wrote:
> On Thu, Jul 15, 2021 at 11:02 AM Andy Shevchenko
> <andy.shevchenko@xxxxxxxxx> wrote:

...

> Now I realize one more item which is missed in the big picture.
> When we have overflowed the denominator (n) and shifted the values, we
> are expecting that the caller will check the rate and use another
> 2^scale (see (6) below) prescaler if needed to drop frequency to the
> needed values. The first few users of this were the drivers of the IPs
> which have an additional prescaler themselves. I dunno if there is any
> flag in CCF to show that the set frequency is 2^scale higher than
> asked.
>
> It means if
>
>         r_o / r_u >> N_lim (5)
>
> we will get m and n *saturated* without this snipped, while with it
> they will be much much better with a nuance that resulting frequency
> is shifted left by
>
>         scale = ln2(r_o/r_u) - nlim (6)
>
> scale bits.

I think I have at some point to introduce a documentation and explain
all this from the thread there.

Mauro, is sphinx capable of producing TeX formulas?

-- 
With Best Regards,
Andy Shevchenko