[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <g24dkwtsobslw6qdvs4vbcdmk2txrlrephm5zmlff2fusrxheo@mqxrprzctymk>
Date: Wed, 5 Apr 2023 16:50:56 +0200
From: Maxime Ripard <maxime@...no.tech>
To: Paul Cercueil <paul@...pouillou.net>
Cc: Aidan MacDonald <aidanmacdonald.0x0@...il.com>,
Stephen Boyd <sboyd@...nel.org>,
Maxime Coquelin <mcoquelin.stm32@...il.com>,
Chen-Yu Tsai <wens@...e.org>, Daniel Vetter <daniel@...ll.ch>,
Nicolas Ferre <nicolas.ferre@...rochip.com>,
Thierry Reding <thierry.reding@...il.com>,
Jaroslav Kysela <perex@...ex.cz>,
Shawn Guo <shawnguo@...nel.org>,
Fabio Estevam <festevam@...il.com>,
Ulf Hansson <ulf.hansson@...aro.org>,
Claudiu Beznea <claudiu.beznea@...rochip.com>,
Michael Turquette <mturquette@...libre.com>,
Dinh Nguyen <dinguyen@...nel.org>,
Chunyan Zhang <zhang.lyra@...il.com>,
Manivannan Sadhasivam <mani@...nel.org>,
Andreas Färber <afaerber@...e.de>,
Jonathan Hunter <jonathanh@...dia.com>,
Abel Vesa <abelvesa@...nel.org>,
Charles Keepax <ckeepax@...nsource.cirrus.com>,
Alessandro Zummo <a.zummo@...ertech.it>,
Peter De Schrijver <pdeschrijver@...dia.com>,
Orson Zhai <orsonzhai@...il.com>,
Alexandre Torgue <alexandre.torgue@...s.st.com>,
Prashant Gaikwad <pgaikwad@...dia.com>,
Liam Girdwood <lgirdwood@...il.com>,
Alexandre Belloni <alexandre.belloni@...tlin.com>,
Samuel Holland <samuel@...lland.org>,
Matthias Brugger <matthias.bgg@...il.com>,
Richard Fitzgerald <rf@...nsource.cirrus.com>,
Vinod Koul <vkoul@...nel.org>,
NXP Linux Team <linux-imx@....com>,
Sekhar Nori <nsekhar@...com>,
Kishon Vijay Abraham I <kishon@...nel.org>,
Linus Walleij <linus.walleij@...aro.org>,
Takashi Iwai <tiwai@...e.com>,
David Airlie <airlied@...il.com>,
Luca Ceresoli <luca.ceresoli@...tlin.com>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
David Lechner <david@...hnology.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Mark Brown <broonie@...nel.org>,
Max Filippov <jcmvbkbc@...il.com>,
Geert Uytterhoeven <geert+renesas@...der.be>,
linux-stm32@...md-mailman.stormreply.com,
alsa-devel@...a-project.org, linux-mediatek@...ts.infradead.org,
linux-phy@...ts.infradead.org, linux-mips@...r.kernel.org,
linux-renesas-soc@...r.kernel.org,
linux-actions@...ts.infradead.org, linux-clk@...r.kernel.org,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@...labora.com>,
patches@...nsource.cirrus.com, linux-tegra@...r.kernel.org,
linux-rtc@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v2 56/65] clk: ingenic: cgu: Switch to determine_rate
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
Download attachment "signature.asc" of type "application/pgp-signature" (229 bytes)
Powered by blists - more mailing lists