From: Maxime Ripard <maxime@cerno.tech>
To: Paul Cercueil <paul@crapouillou.net>
Cc: "Aidan MacDonald" <aidanmacdonald.0x0@gmail.com>,
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Subject: Re: [PATCH v2 56/65] clk: ingenic: cgu: Switch to determine_rate
Date: Wed, 5 Apr 2023 16:50:56 +0200 [thread overview]
Message-ID: <g24dkwtsobslw6qdvs4vbcdmk2txrlrephm5zmlff2fusrxheo@mqxrprzctymk> (raw)
In-Reply-To: <1e0e8e9fe44c27e844e7e918a985704e58da2c27.camel@crapouillou.net>
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On Wed, Apr 05, 2023 at 02:57:26PM +0200, Paul Cercueil wrote:
> Le lundi 27 mars 2023 à 21:24 +0200, Maxime Ripard a écrit :
> > On Fri, Mar 24, 2023 at 08:58:48PM +0000, Aidan MacDonald wrote:
> > > > > My suggestion: add a per-clock bitmap to keep track of which
> > > > > parents
> > > > > are allowed. Any operation that would select a parent clock not
> > > > > on the
> > > > > whitelist should fail. Automatic reparenting should only select
> > > > > from
> > > > > clocks on the whitelist. And we need new DT bindings for
> > > > > controlling
> > > > > the whitelist, for example:
> > > > >
> > > > > clock-parents-0 = <&clk1>, <&pll_c>;
> > > > > clock-parents-1 = <&clk2>, <&pll_a>, <&pll_b>;
> > > > >
> > > > > This means that clk1 can only have pll_c as a parent, while
> > > > > clk2 can
> > > > > have pll_a or pll_b as parents. By default every clock will be
> > > > > able
> > > > > to use any parent, so a list is only needed if the machine
> > > > > needs a
> > > > > more restrictive policy.
> > > > >
> > > > > assigned-clock-parents should disable automatic reparenting,
> > > > > but allow
> > > > > explicit clk_set_parent(). This will allow clock drivers to
> > > > > start doing
> > > > > reparenting without breaking old DTs.
> > > >
> > > > I'm generally not a fan of putting all these policies in the
> > > > device
> > > > tree. Do you have an example where it wouldn't be possible to do
> > > > exactly
> > > > this from the driver itself?
> > >
> > > I'm confused. What's implicit in the example is clk1 and clk2 might
> > > have *other* possible choices of parent clock and the device tree
> > > is
> > > limiting what the OS is allowed to choose.
> > >
> > > Why would you put such arbitrary limitations into the driver?
> >
> > Why would we put such arbitrary limitations in the firmware? As this
> > entire thread can attest, people are already using the device tree to
> > work around the limitations of the Linux driver, or reduce the
> > features of Linux because they can rely on the device tree. Either
> > way, it's linked to the state of the Linux driver, and any other OS
> > or
> > Linux version could very well implement something more dynamic.
>
> Probably because if we have to choose between setting policy in the
> kernel or in the firmware, it is arguably better to set it in the
> firmware.
I have a very different view on this I guess. Firmware is (most of the
time) hard to update, and the policy depend on the state of support of a
given OS so it's likely to evolve. The kernel is the best place to me to
put that kind of policy. Why do you think differently?
> Especially when talking about clocks, as the firmware is already the
> one programming the boot clocks.
I'm not sure what your point is there. I don't think I ever saw a
firmware getting the clocks right for every possible scenario on a given
platform. And if it was indeed the case, then we wouldn't even a kernel
driver.
Maxime
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next prev parent reply other threads:[~2023-04-05 14:51 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20221018-clk-range-checks-fixes-v2-0-f6736dec138e@cerno.tech>
[not found] ` <20221018-clk-range-checks-fixes-v2-56-f6736dec138e@cerno.tech>
2022-11-04 14:31 ` [PATCH v2 56/65] clk: ingenic: cgu: Switch to determine_rate Paul Cercueil
2022-11-04 14:59 ` Maxime Ripard
2022-11-04 17:35 ` Aidan MacDonald
2022-11-07 8:54 ` Maxime Ripard
2022-11-07 20:57 ` Aidan MacDonald
2022-11-09 11:00 ` Maxime Ripard
[not found] ` <06a293adc75990ed3e297b076fc38d8a.sboyd@kernel.org>
2023-03-23 15:35 ` Aidan MacDonald
2023-03-24 11:19 ` Maxime Ripard
2023-03-24 20:58 ` Aidan MacDonald
2023-03-27 19:24 ` Maxime Ripard
2023-04-05 12:57 ` Paul Cercueil
2023-04-05 14:50 ` Maxime Ripard [this message]
2023-04-05 15:29 ` Paul Cercueil
2022-11-05 10:33 ` Paul Cercueil
2022-11-09 10:53 ` Maxime Ripard
2022-11-09 11:36 ` Paul Cercueil
[not found] ` <20221018-clk-range-checks-fixes-v2-43-f6736dec138e@cerno.tech>
2022-11-04 15:44 ` [PATCH v2 43/65] ASoC: tlv320aic32x4: Add a determine_rate hook Mark Brown
2022-11-04 15:51 ` Maxime Ripard
2022-11-04 15:59 ` Mark Brown
2022-11-07 8:43 ` Maxime Ripard
2022-11-07 12:06 ` Mark Brown
2022-11-07 15:26 ` Maxime Ripard
2022-11-07 16:02 ` Mark Brown
[not found] ` <5819b1362f35ce306e1b6d566bfd44e5.sboyd@kernel.org>
2023-03-29 19:50 ` Maxime Ripard
[not found] ` <20221018-clk-range-checks-fixes-v2-21-f6736dec138e@cerno.tech>
2022-11-04 16:45 ` [PATCH v2 21/65] clk: davinci: da8xx-cfgchip: " David Lechner
2022-11-07 12:06 ` Maxime Ripard
2022-11-07 14:52 ` David Lechner
[not found] ` <20221018-clk-range-checks-fixes-v2-22-f6736dec138e@cerno.tech>
2022-11-04 16:46 ` [PATCH v2 22/65] " David Lechner
[not found] ` <20221018-clk-range-checks-fixes-v2-54-f6736dec138e@cerno.tech>
2022-11-04 16:49 ` [PATCH v2 54/65] clk: da8xx: clk48: Switch to determine_rate David Lechner
2022-11-07 14:52 ` Maxime Ripard
[not found] ` <20221018-clk-range-checks-fixes-v2-28-f6736dec138e@cerno.tech>
2022-11-07 7:51 ` [PATCH v2 28/65] clk: renesas: r9a06g032: Add a determine_rate hook Geert Uytterhoeven
[not found] ` <20221018-clk-range-checks-fixes-v2-65-f6736dec138e@cerno.tech>
2022-11-07 10:56 ` [PATCH v2 65/65] clk: Warn if we register a mux without determine_rate Charles Keepax
[not found] ` <20221018-clk-range-checks-fixes-v2-20-f6736dec138e@cerno.tech>
2022-11-07 10:58 ` [PATCH v2 20/65] clk: wm831x: clkout: Add a determine_rate hook Charles Keepax
[not found] ` <20221018-clk-range-checks-fixes-v2-34-f6736dec138e@cerno.tech>
2022-11-08 13:25 ` [PATCH v2 34/65] clk: ux500: prcmu: " Linus Walleij
2022-11-09 11:05 ` Maxime Ripard
[not found] ` <20221018-clk-range-checks-fixes-v2-35-f6736dec138e@cerno.tech>
2022-11-08 13:27 ` [PATCH v2 35/65] clk: ux500: sysctrl: " Linus Walleij
2022-11-10 11:28 ` Ulf Hansson
2022-11-10 11:39 ` Linus Walleij
2022-11-10 13:05 ` Ulf Hansson
2022-11-11 9:20 ` Linus Walleij
2022-11-14 9:05 ` Lee Jones
[not found] ` <20221018-clk-range-checks-fixes-v2-58-f6736dec138e@cerno.tech>
2022-11-09 2:43 ` [PATCH v2 58/65] clk: sprd: composite: Switch to determine_rate Chunyan Zhang
[not found] ` <20221018-clk-range-checks-fixes-v2-13-f6736dec138e@cerno.tech>
2022-11-13 22:35 ` [PATCH v2 13/65] clk: lmk04832: clkout: Add a determine_rate hook Liam Beguin
[not found] ` <f804380a14c346fdbbf3286bcb40b3c2.sboyd@kernel.org>
2023-03-22 10:01 ` [PATCH v2 00/65] clk: Make determine_rate mandatory for muxes Maxime Ripard
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