linux-kernel - Re: [PATCH v2 2/7] ACPI / LPSS: allow to use specific PM domain during ->probe()

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Date:	Fri, 4 Dec 2015 15:04:07 +0200
From:	Jarkko Nikula <jarkko.nikula@...ux.intel.com>
To:	"Shevchenko, Andriy" <andriy.shevchenko@...el.com>,
	"rjw@...ysocki.net" <rjw@...ysocki.net>
Cc:	"Koul, Vinod" <vinod.koul@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
	"mika.westerberg@...ux.intel.com" <mika.westerberg@...ux.intel.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>
Subject: Re: [PATCH v2 2/7] ACPI / LPSS: allow to use specific PM domain
 during ->probe()

On 12/03/2015 09:29 PM, Shevchenko, Andriy wrote:
> I briefly checked this for DMA issue. It will not help anyhow, so we
> *have to* move a power domain assignment to the BIND stage.
>
> For I2C and rest LPSS devices this might help (though didn't look
> deeply). My understanding that we assign those callbacks in the LPSS
> custom PM domain and call them explicitly in acpi_lpss.c.
>
> The code will be the same as we are using now to bring device from
> runtime suspend resume. This means whenever we call probe for e.g. I2C
> we end up in a sequence similar to:
>   pm_runtime_resume(I2C);
>   ->probe(I2C);
>   pm_runtime_suspend(I2C);
>
> I will try to mock up this and check if it will work, though have no
> idea what to do if I2C during probe calls pm_runtime_forbid().
>
> Jarkko, what do you think?
>
I suppose device core will handle it. If the runtime PM is forbidden or 
not initialized at all the device shouldn't idle.

-- 
Jarkko
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