linux-kernel - Re: [PATCH v2 2/3] clk: fractional-divider: Introduce NO

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Date:   Thu, 22 Jul 2021 12:38:15 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Liu Ying <victor.liu@....com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Elaine Zhang <zhangqing@...k-chips.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-kernel@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org,
        Michael Turquette <mturquette@...libre.com>,
        NXP Linux Team <linux-imx@....com>,
        Jacky Bai <ping.bai@....com>
Subject: Re: [PATCH v2 2/3] clk: fractional-divider: Introduce NO_PRESCALER flag

On Thu, Jul 22, 2021 at 12:33 PM Liu Ying <victor.liu@....com> wrote:
> On Fri, 2021-07-16 at 16:34 +0300, Andy Shevchenko wrote:
> > The newly introduced flag, when set, makes the flow to skip
> > the assumption that the caller will use an additional 2^scale
> > prescaler to get the desired clock rate.
>
> As I mentioned in v1 comment, it seems to be good to decouple the
> prescaler knowledge from this common fractional divider clk driver.
> This way, we'll make it simpler and easier to maintain. Also, then, the
> NO_PRESCALER flag is not needed at all.  However, it seems that two
> Intel drivers which use the frational divider drivers will be affected
> and rate negotiation logics need to be implemented for them.  Please
> consider if it's doable or not.

The current driver works for the certain hardware without this change.
If you think it's better, submit a proposal we will discuss.

> If we ultimately keep the prescaler knowledge here, please consider to
> add the NO_PRESCALER flag for i.MX7ulp as it hasn't the prescaler IIUC.

You mean there is a code which is currently using this driver w/o
taking into account this prescaller flavour? Can you, please, point
out, I'll definitely update it. Thanks for the catch!

-- 
With Best Regards,
Andy Shevchenko