linux-kernel - Re: [PATCH v1 08/11] clk: move meson clk-regmap implementation to common code

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Message-ID: <e53adbf9fdf6e3f142083b0d40d074ca.sboyd@kernel.org>
Date: Tue, 03 Dec 2024 14:50:31 -0800
From: Stephen Boyd <sboyd@...nel.org>
To: Conor Dooley <conor.dooley@...rochip.com>
Cc: Conor Dooley <conor@...nel.org>, Jerome Brunet <jbrunet@...libre.com>, Neil Armstrong <neil.armstrong@...aro.org>, linux-kernel@...r.kernel.org, Daire McNamara <daire.mcnamara@...rochip.com>, pierre-henry.moussay@...rochip.com, valentina.fernandezalanis@...rochip.com, Michael Turquette <mturquette@...libre.com>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Jassi Brar <jassisinghbrar@...il.com>, Lee Jones <lee@...nel.org>, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Kevin Hilman <khilman@...libre.com>, Martin Blumenstingl <martin.blumenstingl@...glemail.com>, Philipp Zabel <p.zabel@...gutronix.de>, linux-riscv@...ts.infradead.org, linux-clk@...r.kernel.org, devicetree@...r.kernel.org, linux-amlogic@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v1 08/11] clk: move meson clk-regmap implementation to common code

Quoting Conor Dooley (2024-11-28 02:36:16)
> On Thu, Nov 14, 2024 at 05:29:54PM -0800, Stephen Boyd wrote:
> > Quoting Conor Dooley (2024-11-06 04:56:25)
> > > My use case doesn't
> > > actually need the registration code changes either as, currently, only reg
> > > gets set at runtime, but leaving that out is a level of incomplete I'd not
> > > let myself away with.
> > > Obviously shoving the extra members into the clk structs has the downside
> > > of taking up a pointer and a offset worth of memory for each clock of
> > > that type registered, but it is substantially easier to support devices
> > > with multiple regmaps that way. Probably moot though since the approach you
> > > suggested in the thread linked above that implements a clk_hw_get_regmap()
> > > has to store a pointer to the regmap's identifier which would take up an
> > > identical amount of memory.
> > 
> > We don't need to store the regmap identifier in the struct clk. We can
> > store it in the 'struct clk_init_data' with some new field, and only do
> > that when/if we actually need to. We would need to pass the init data to
> > the clk_ops::init() callback though. We currently knock that out during
> > registration so that clk_hw->init is NULL. Probably we can just set that
> > to NULL after the init routine runs in __clk_core_init().
> > 
> > Long story short, don't add something to 'struct clk_core', 'struct
> > clk', or 'struct clk_hw' for these details. We can have a 'struct
> > clk_regmap_hw' that everyone else can build upon:
> > 
> >   struct clk_regmap_hw {
> >         struct regmap *regmap;
> >         struct clk_hw hw;
> >   };
> 
> What's the point of this? I don't understand why you want to do this over
> what clk_divider et al already do, where clk_hw and the iomem pointer
> are in the struct itself.

Can you give an example? I don't understand what you're suggesting. I
prefer a struct clk_regmap_hw like above so that the existing struct
clk_hw in the kernel aren't increased by a pointer. SoC drivers can use
the same struct as a replacement for their struct clk_hw member today.