linux-kernel - Re: [PATCH v3 2/3] clk: renesas: Add family-specific clock driver for RZ/V2H(P)

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Message-ID: <CAMuHMdVyqBmipMLeYd0nw3kEHwc=RvWJvrD8EYKVt+36E7oS+A@mail.gmail.com>
Date: Fri, 12 Jul 2024 19:11:38 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Philipp Zabel <p.zabel@...gutronix.de>, Magnus Damm <magnus.damm@...il.com>, 
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-renesas-soc@...r.kernel.org, 
	Biju Das <biju.das.jz@...renesas.com>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v3 2/3] clk: renesas: Add family-specific clock driver for RZ/V2H(P)

Hi Prabhakar,

On Fri, Jul 12, 2024 at 5:29 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
> On Fri, Jul 12, 2024 at 4:23 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Fri, Jul 12, 2024 at 5:14 PM Lad, Prabhakar
> > <prabhakar.csengg@...il.com> wrote:
> > > On Fri, Jul 12, 2024 at 12:59 PM Geert Uytterhoeven
> > > > On Thu, Jun 27, 2024 at 6:14 PM Prabhakar <prabhakar.csengg@...il.com> wrote:
> > > > > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > >
> > > > > Add family-specific clock driver for RZ/V2H(P) SoCs.
> > > > >
> > > > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > > > > ---
> > > > > v2->v3
> > > > > - Dropped num_hw_resets from struct rzv2h_cpg_priv
> > > > > - Dropped range_check for module clocks
> > > > > - Made mon_index to s8 instead of u8 in struct rzv2h_mod_clk
> > > > > - Added support for critical module clocks with DEF_MOD_CRITICAL
> > > > > - Added check for mon_index in rzv2h_mod_clock_endisable and
> > > > >   rzv2h_mod_clock_is_enabled()
> >
> > > > > --- /dev/null
> > > > > +++ b/drivers/clk/renesas/rzv2h-cpg.h
> >
> > > > > +/**
> > > > > + * struct rzv2h_reset - Reset definitions
> > > > > + *
> > > > > + * @reset_index: reset register index
> > > > > + * @reset_bit: reset bit
> > > > > + * @mon_index: monitor register index
> > > > > + * @mon_bit: monitor bit
> > > > > + */
> > > > > +struct rzv2h_reset {
> > > > > +       u8 reset_index;
> > > > > +       u8 reset_bit;
> > > > > +       u8 mon_index;
> > > > > +       u8 mon_bit;
> > > > > +};
> > > > > +
> > > > > +#define RST_ID(x, y)   ((((x) * 16)) + (y))
> > > > > +
> > > > > +#define DEF_RST_BASE(_id, _resindex, _resbit, _monindex, _monbit)      \
> > > > > +       [_id] = { \
> > > >
> > > > Indexing by _id means the reset array will be very sparse.  E.g. the
> > > > innocent-looking r9a09g057_resets[] with only a single entry takes
> > > > 600 bytes.
> > > >
> > > > If you do need the full array for indexing, please allocate and
> > > > populate it at runtime.
> > > >
> > > OK, I will use the radix tree for resets (is that OK)?
> >
> > You mean XArray? include/linux/radix-tree.h has:
> >
> >     /* Keep unconverted code working */
> >     #define radix_tree_root         xarray
> >     #define radix_tree_node         xa_node
> >
> Yes, I meant the above.
>
> > Given a single xa_node is already 576 bytes, just allocating the full
> > linear reset array at runtime is probably better.
> >
> Agreed, I will create a linear reset array and loop through the array
> based on reset index and reset bit to match with id whenever required.

With a full allocated linear reset array you do not need to loop,
but you can just index it by the reset ID??

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds