linux-kernel - Re: [PATCH/RFC 00/03] irqchip: renesas-irqc: Fine grained Runtime PM support

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Message-ID: <CAMuHMdWtUYoFWWfijFbQCv6Z-phZW2XN+F5n1zfqbZMFGjM+Bg@mail.gmail.com>
Date:	Thu, 23 Apr 2015 19:49:59 +0200
From:	Geert Uytterhoeven <geert@...ux-m68k.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Magnus Damm <magnus.damm@...il.com>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	Jason Cooper <jason@...edaemon.net>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Simon Horman <horms@...ge.net.au>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH/RFC 00/03] irqchip: renesas-irqc: Fine grained Runtime PM support

On Thu, Apr 23, 2015 at 4:44 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> On Thu, 23 Apr 2015, Geert Uytterhoeven wrote:
>> >> I'm afraid you can't call pm_runtime_get_sync() from these methods, as
>> >> they may be called from interrupt context.
>> >
>> > Ouch. I know the clock framework has prepare/enable separated with
>> > context, but with the irqchip callbacks I suppose no such separation
>>
>> It's not the clock operations, but the pm_runtime operations that cannot be
>> called from interrupt context.
>
> In fact the pm_runtime operations _can_ be called from interrupt
> context, provided the driver has first invoked pm_runtime_irq_safe().
> Of course, this requires that none of the runtime-PM callback routines
> ever sleep or perform a blocking operation.
>
> This is all explained in Documentation/power/runtime_pm.txt (search for
> "irq_safe").

Perhaps that can help. We'll have to give it a try...

I've always found this a bit strange when PM Domains are involved:
pm_runtime_irq_safe(dev) applies to device dev, while the actual callbacks
belong to the PM Domain code (the device's driver doesn't have any).

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

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
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