linux-kernel - Re: [PATCH v2 06/13] pinctrl: renesas: pinctrl-rzg2l: Add function pointers for locking/unlocking the PFC register

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Message-ID: <CAMuHMdUJXdEG-BQRYNbmhbGCtE+O1uWO0j-PkBaF7S_Qyp8M-Q@mail.gmail.com>
Date: Wed, 22 May 2024 14:23:15 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Prabhakar <prabhakar.csengg@...il.com>, Linus Walleij <linus.walleij@...aro.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Magnus Damm <magnus.damm@...il.com>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>, 
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	Fabrizio Castro <fabrizio.castro.jz@...esas.com>, 
	Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: Re: [PATCH v2 06/13] pinctrl: renesas: pinctrl-rzg2l: Add function
 pointers for locking/unlocking the PFC register

Hi Biju,

On Tue, Apr 23, 2024 at 8:12 PM Biju Das <biju.das.jz@...renesas.com> wrote:
> > -----Original Message-----
> > From: Prabhakar <prabhakar.csengg@...il.com>
> > Sent: Tuesday, April 23, 2024 6:59 PM
> > Subject: [PATCH v2 06/13] pinctrl: renesas: pinctrl-rzg2l: Add function pointers for
> > locking/unlocking the PFC register
> >
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >
> > On the RZ/G2L SoC, the PFCWE bit controls writing to PFC registers.
> > However, on the RZ/V2H(P) SoC, the PFCWE (REGWE_A on RZ/V2H) bit controls writing to both PFC and
> > PMC registers. Additionally, BIT(7) B0WI is undocumented for the PWPR register on RZ/V2H(P) SoC. To
> > accommodate these differences across SoC variants, introduce the set_pfc_mode() and
> > pm_set_pfc() function pointers.
> >
> > Note, in rzg2l_pinctrl_set_pfc_mode() the pwpr_pfc_unlock() call is now called before PMC
> > read/write and pwpr_pfc_lock() call is now called after PMC read/write this is to keep changes
> > minimal for RZ/V2H(P).
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > ---
> > RFC->v2
> > - Introduced function pointer for (un)lock

> > --- a/drivers/pinctrl/renesas/pinctrl-rzg2l.c
> > +++ b/drivers/pinctrl/renesas/pinctrl-rzg2l.c
> > @@ -2688,6 +2699,8 @@ static struct rzg2l_pinctrl_data r9a07g043_data = {
> >       .variable_pin_cfg = r9a07g043f_variable_pin_cfg,
> >       .n_variable_pin_cfg = ARRAY_SIZE(r9a07g043f_variable_pin_cfg),
> >  #endif
> > +     .pwpr_pfc_unlock = &rzg2l_pwpr_pfc_unlock,
> > +     .pwpr_pfc_lock = &rzg2l_pwpr_pfc_lock,
> >  };
> >
> >  static struct rzg2l_pinctrl_data r9a07g044_data = { @@ -2699,6 +2712,8 @@ static struct
> > rzg2l_pinctrl_data r9a07g044_data = {
> >       .n_dedicated_pins = ARRAY_SIZE(rzg2l_dedicated_pins.common) +
> >               ARRAY_SIZE(rzg2l_dedicated_pins.rzg2l_pins),
> >       .hwcfg = &rzg2l_hwcfg,
> > +     .pwpr_pfc_unlock = &rzg2l_pwpr_pfc_unlock,
> > +     .pwpr_pfc_lock = &rzg2l_pwpr_pfc_lock,
> >  };
> >
> >  static struct rzg2l_pinctrl_data r9a08g045_data = { @@ -2709,6 +2724,8 @@ static struct
> > rzg2l_pinctrl_data r9a08g045_data = {
> >       .n_port_pins = ARRAY_SIZE(r9a08g045_gpio_configs) * RZG2L_PINS_PER_PORT,
> >       .n_dedicated_pins = ARRAY_SIZE(rzg3s_dedicated_pins),
> >       .hwcfg = &rzg3s_hwcfg,
> > +     .pwpr_pfc_unlock = &rzg2l_pwpr_pfc_unlock,
> > +     .pwpr_pfc_lock = &rzg2l_pwpr_pfc_lock,
>
> Some memory can be saved by avoiding duplication of data by using
> a single pointer for structure containing function pointers??
>
> struct rzg2l_pinctrl_fns {
>         void (*pwpr_pfc_unlock)(struct rzg2l_pinctrl *pctrl);
>         void (*pwpr_pfc_lock)(struct rzg2l_pinctrl *pctrl);
> }

So that would replace 3 (4 after adding RZ/V2H support) x 2 pointers in
rzg2l_pinctrl_data structures by 3 (4) pointers in rzg2l_pinctrl_data
structures + 1 (2) x 2 pointers in rzg2l_pinctrl_fns structures, and
code size would increase due to extra pointer dereferences before
each call.
Am I missing something?

Merging rzg2l_pwpr_pfc_{,un}lock() into a single function (taking a
"bool lock" flag) might be a better solution to reduce rzg2l_pinctrl_data size.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68korg

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