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

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Message-ID: <CA+V-a8vABF6vg+J7DAGzgnw8612oe6VfJkc5y-krySvnpAnPkQ@mail.gmail.com>
Date: Fri, 12 Jul 2024 16:13:10 +0100
From: "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
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 Geert,

Thank you for the review.

On Fri, Jul 12, 2024 at 12:59 PM Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
>
> Hi Prabhakar,
>
> 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()
>
> Thanks for the update!
>
> > --- /dev/null
> > +++ b/drivers/clk/renesas/rzv2h-cpg.c
>
> > +static struct clk * __init
> > +rzv2h_cpg_pll_clk_register(const struct cpg_core_clk *core,
> > +                          struct rzv2h_cpg_priv *priv,
> > +                          const struct clk_ops *ops)
> > +{
> > +       void __iomem *base = priv->base;
> > +       struct clk **clks = priv->clks;
> > +       struct device *dev = priv->dev;
> > +       struct clk_init_data init;
> > +       const struct clk *parent;
> > +       const char *parent_name;
> > +       struct pll_clk *pll_clk;
> > +
> > +       parent = clks[core->parent & 0xffff];
>
> No need to mask with 0xffff, as nothing is ever stored in the high bits.
>
OK, I will drop it.

> > +static void __init
> > +rzv2h_cpg_register_mod_clk(const struct rzv2h_mod_clk *mod,
> > +                          struct rzv2h_cpg_priv *priv)
> > +{
> > +       struct mod_clock *clock = NULL;
> > +       struct device *dev = priv->dev;
> > +       struct clk_init_data init;
> > +       unsigned int id = mod->id;
>
> This is the sole user of mod->id, which can be calculated easily from
> mod->on_index and mod->on_bit.
>
Agreed, I will drop id.

> > --- /dev/null
> > +++ b/drivers/clk/renesas/rzv2h-cpg.h
>
> > +/**
> > + * struct rzv2h_mod_clk - Module Clocks definitions
> > + *
> > + * @name: handle between common and hardware-specific interfaces
> > + * @parent: id of parent clock
> > + * @id: clock index in array containing all Core and Module Clocks
> > + * @critical: flag to indicate the clock is critical
> > + * @on_index: control register index
> > + * @on_bit: ON bit
> > + * @mon_index: monitor register index
> > + * @mon_bit: monitor bit
> > + */
> > +struct rzv2h_mod_clk {
> > +       const char *name;
> > +       unsigned int parent;
> > +       unsigned int id;
>
> No need to store the id, as it can be calculated when needed.
>
OK.

> > +       bool critical;
> > +       u8 on_index;
> > +       u8 on_bit;
> > +       s8 mon_index;
> > +       u8 mon_bit;
>
> That leaves us with 1 64-bit pointer, 1 32-bit integer, and 5 bytes.
> Using bitfields for the latter is complicated due to the mix of signed
> and unsigned values.
> However, parent can be reduced to u16, shaving off one 64-bit word
> from each entry.
>
Agreed, I will update parent to u16.

> > +};
>
> > +/**
> > + * 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)?

> As a bonus, you would no longer need rzv2h_cpg_info.info, and
> r9a09g057_resets[] and r9a09g057_cpg_info[] can become __initconst.
>
Agreed (and also r9a09g057_mod_clks).

Cheers,
Prabhakar