linux-kernel - Re: [PATCH 1/15] clk: divider: Make divider_round

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Date:   Thu, 9 Mar 2017 11:55:35 +0100
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Mike Turquette <mturquette@...libre.com>,
        Chen-Yu Tsai <wens@...e.org>, dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com,
        Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Sylvain Lemieux <slemieux.tyco@...il.com>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
        linux-amlogic@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-soc@...r.kernel.org, rtc-linux@...glegroups.com
Subject: Re: [PATCH 1/15] clk: divider: Make divider_round_rate take the
 parent clock

Hi Stephen,

On Tue, Mar 07, 2017 at 06:11:57AM -0800, Stephen Boyd wrote:
> On 03/07, Maxime Ripard wrote:
> > So far, divider_round_rate only considers the parent clock returned by
> > clk_hw_get_parent.
> > 
> > This works fine on clocks that have a single parents, this doesn't work on
> > muxes, since we will only consider the first parent, while other parents
> > may totally be able to provide a better combination.
> > 
> > Clocks in that case cannot use divider_round_rate, so would have to come up
> > with a very similar logic to work around it. Instead of having to do
> > something like this, and duplicate that logic everywhere, give an
> > additional parameter for the parent clock to consider.
> > 
> > Current users have been converted using the following coccinelle script
> > 
> > @@
> > identifier hw, rate, prate, table, width, flags;
> > @@
> > 
> > -long divider_round_rate(struct clk_hw *hw,
> > +long divider_round_rate(struct clk_hw *hw, struct clk_hw *parent,
> >                         unsigned long rate,
> >                         unsigned long *prate,
> >                         const struct clk_div_table *table,
> >                         u8 width,
> >                         unsigned long flags) { ... }
> > 
> > @@
> > identifier fn, hw;
> > expression E2, E3, E4, E5, E6;
> > @@
> >  fn (struct clk_hw *hw, ...) {
> >  <...
> > -divider_round_rate(hw, E2, E3, E4, E5, E6)
> > +divider_round_rate(hw, clk_hw_get_parent(hw), E2, E3, E4, E5, E6)
> >  ...>
> > }
> 
> Why not introduce another function like 
> 
> 	divider_round_rate_parent()
> 	divider_round_rate_mux()
> 
> that takes the extra parent argument? Technically, a divider is
> considered to only have one parent, and if it has more than one
> parent, then it is a mux and a divider.

Yes, that would work too, without needing the cross tree change. I'll
do that in the next version.

Thanks!
Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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