linux-kernel - Re: [PATCH v2 2/3] ARM: at91: pm: add per soc validation of pm modes

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Date:   Tue, 4 Aug 2020 17:08:41 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Claudiu.Beznea@...rochip.com
Cc:     Nicolas.Ferre@...rochip.com, Ludovic.Desroches@...rochip.com,
        wenyou.yang@...el.com, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/3] ARM: at91: pm: add per soc validation of pm modes

On 04/08/2020 15:00:38+0000, Claudiu.Beznea@...rochip.com wrote:
> 
> 
> On 04.08.2020 14:42, Alexandre Belloni wrote:
> > EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> > 
> > Hello,
> > 
> > On 04/08/2020 14:07:37+0300, Claudiu Beznea wrote:
> >>  void __init at91rm9200_pm_init(void)
> >>  {
> >> +     static const int modes[] __initconst = {
> > 
> > You don't need that to be static as it is now local to the function.
> > 
> >> +             AT91_PM_STANDBY, AT91_PM_ULP0
> >> +     };
> >> +
> >>       if (!IS_ENABLED(CONFIG_SOC_AT91RM9200))
> >>               return;
> >>
> >> +     at91_pm_modes_validate(modes, ARRAY_SIZE(modes));
> > 
> > For rm9200 and at91sam9, I would not allow changing the pm_modes and
> > simply enforce standby_mode = AT91_PM_STANDBY and suspend_mode =
> > AT91_PM_ULP0.I don't think you have any user that ever changed that
> > behaviour also that avoids increasing the boot time for those slow SoCs.
> 
> OK, but bootargs is parsed at a moment when there is no information about
> the machine that is running the code. And enforcing this in *_pm_init()
> functions for rm9200 and at91sam9 may change suspend and standby mode that
> user selected. If there is no user up to this moment there is still the
> possibility of being one in the future.
> 

So let's prevent users from doing that. Unused arguments are silently
ignored which is exactly what we want to do. You won't make me believe
there is actually a use case for swapping the standby and suspend
meanings.

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com