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

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Message-ID: <9117e5212a3b743ca541918ec2b701c159ac752c.camel@nxp.com>
Date:   Thu, 22 Jul 2021 17:29:23 +0800
From:   Liu Ying <victor.liu@....com>
To:     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
Cc:     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 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.

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.

Regards,
Liu Ying

> 
> Reported-by: Liu Ying <victor.liu@....com>
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> ---
> v2: moved entire snipped under new flag check (Liu)
>  drivers/clk/clk-fractional-divider.c | 10 ++++++----
>  include/linux/clk-provider.h         |  5 +++++
>  2 files changed, 11 insertions(+), 4 deletions(-)