linux-kernel - Re: [PATCH 07/17] clk: renesas: rzg2l: Extend power domain support

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Message-ID: <CAMuHMdX0HDK2w1N-k_R9ud_CVotRgAd2CjOoHTsWkSE_Rb7zyQ@mail.gmail.com>
Date: Mon, 19 Feb 2024 09:48:53 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: claudiu beznea <claudiu.beznea@...on.dev>
Cc: mturquette@...libre.com, sboyd@...nel.org, robh@...nel.org, 
	krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org, magnus.damm@...il.com, 
	paul.walmsley@...ive.com, palmer@...belt.com, aou@...s.berkeley.edu, 
	linux-renesas-soc@...r.kernel.org, linux-clk@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, 
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 07/17] clk: renesas: rzg2l: Extend power domain support

Hi Claudiu,

On Mon, Feb 19, 2024 at 9:24 AM claudiu beznea <claudiu.beznea@...on.dev> wrote:
> On 16.02.2024 16:08, Geert Uytterhoeven wrote:
> > On Thu, Feb 8, 2024 at 1:44 PM Claudiu <claudiu.beznea@...on.dev> wrote:
> >> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >>
> >> RZ/{G2L, V2L, G3S}-based CPG versions have support for saving extra
> >> power when clocks are disabled by activating module standby. This is done
> >> through MSTOP-specific registers that are part of CPG. Each individual
> >> module has one or more bits associated with one MSTOP register (see table
> >> "Registers for Module Standby Mode" from HW manuals). Hardware manual
> >> associates modules' clocks with one or more MSTOP bits. There are 3 mappings
> >> available (identified by researching RZ/G2L, RZ/G3S, RZ/V2L HW manuals):
> >>
> >> case 1: N clocks mapped to N MSTOP bits (with N={0, ..., X})
> >> case 2: N clocks mapped to 1 MSTOP bit  (with N={0, ..., X})
> >> case 3: N clocks mapped to M MSTOP bits (with N={0, ..., X}, M={0, ..., Y})
> >>
> >> Case 3 has been currently identified on RZ/V2L for the VCPL4 module.
> >>
> >> To cover all three cases, the individual platform drivers will provide to
> >> clock driver MSTOP register offset and associated bits in this register
> >> as a bitmask and the clock driver will apply this bitmask to proper
> >> MSTOP register.
> >>
> >> Apart from MSTOP support, RZ/G3S can save more power by powering down the
> >> individual IPs (after MSTOP has been set) if proper bits in
> >> CPG_PWRDN_IP{1,2} registers are set.
> >>
> >> The MSTOP and IP power down support were implemented through power
> >> domains. Platform-specific clock drivers will register an array of
> >> type struct rzg2l_cpg_pm_domain_init_data, which will be used to
> >> instantiate properly the power domains.
> >>
> >> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >
> > Thanks for your patch!
> >
> >> --- a/drivers/clk/renesas/rzg2l-cpg.c
> >> +++ b/drivers/clk/renesas/rzg2l-cpg.c
> >> @@ -1559,9 +1556,34 @@ static bool rzg2l_cpg_is_pm_clk(struct rzg2l_cpg_priv *priv,
> >>         return true;
> >>  }
> [ ... ]
>
> >
> >> @@ -234,6 +246,54 @@ struct rzg2l_reset {
> >>  #define DEF_RST(_id, _off, _bit)       \
> >>         DEF_RST_MON(_id, _off, _bit, -1)
> >>
> >> +/**
> >> + * struct rzg2l_cpg_pm_domain_conf - PM domain configuration data structure
> >> + * @mstop: MSTOP configuration (MSB = register offset, LSB = bitmask)
> >> + * @pwrdn: PWRDN configuration (MSB = register offset, LSB = register bit)
> >> + */
> >> +struct rzg2l_cpg_pm_domain_conf {
> >> +       u32 mstop;
> >> +       u32 pwrdn;
> >
> > Why not
> >
> >     u16 mstop_off;
> >     u16 mstop_mask;
> >     u16 pwrdn_off;
> >     u16 pwrdn_mask;
> >
> > so you can drop the MSTOP*() and PWRDN*() macros below?
>
> I did it like this to align with the already existing approach for this
> kind of things available in this driver. I can do it as you proposed.

The other fields do not align nicely with byte or word boundaries.

I can see the value of the MSTOP(name, bitmask) and
PWRDN(name, bitmask) macros, but I'd rather get rid of the *_MASK()
and *_OFF() variants.

> For the rest of your comments on this patch: I agree and will adjust the
> patch in the next version.

Thanks!

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