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

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Message-ID: <ba089899-3625-43b2-9ba4-f2fb0e8ac03e@tuxon.dev>
Date: Mon, 19 Feb 2024 11:04:36 +0200
From: claudiu beznea <claudiu.beznea@...on.dev>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
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, Geert,

On 19.02.2024 10:48, Geert Uytterhoeven wrote:
> 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.

Sure, I'll do proper adjustments in the next version.

Thank you,
Claudiu Beznea

> 
>> 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
>