linux-kernel - Re: [PATCH 4/6] pinctrl: single: Add support for wake-up interrupts

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Message-ID: <20131011154804.GP29913@atomide.com>
Date:	Fri, 11 Oct 2013 08:48:05 -0700
From:	Tony Lindgren <tony@...mide.com>
To:	Balaji T K <balajitk@...com>
Cc:	Roger Quadros <rogerq@...com>,
	Linus Walleij <linus.walleij@...aro.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	Haojian Zhuang <haojian.zhuang@...aro.org>,
	Benoît Cousson <bcousson@...libre.com>,
	Linux-OMAP <linux-omap@...r.kernel.org>
Subject: Re: [PATCH 4/6] pinctrl: single: Add support for wake-up interrupts

* Balaji T K <balajitk@...com> [131011 08:51]:
> On Friday 11 October 2013 09:06 PM, Tony Lindgren wrote:
> >>>What the pin control driver should do is control the pins. Whether the registers
> >>>are spread out in the entire IO-memory does not matter. We did have one system
> >>>which placed the IO-muxing together with each peripheral (!) and I did
> >>>still want
> >>>that to be handled by a single pinctrl driver picking out windows to all these
> >>>IO-ranges.
> >>>
> >>>Things like the PRM which has (my guess) a gazillion registers related to its
> >>>deep-core SoC stuff should be handled by things like
> >>>drivers/mfd/syscon.c, which means it is dead simple for some other driver
> >>>using "just this one register" in that range to get a handle at it and poke it
> >>>using syscon_node_to_regmap() (just derference an ampersand ref)
> >>>syscon_regmap_lookup_by_compatible() (use a compatible string)
> >>>all returning a regmap * that you can use to poke these registers.
> >>
> >>The register handling is fine. But how do we deal with resource handling?
> >>e.g. the block that has the deep-core registers might need to be clocked or powered
> >>before the registers can be accessed.
> >
> >Right, that's the key issue here. The register access would have to be conditional
> >based on the hardware modules PM state. Otherwise we'll have hard to trace hangs
> >and oopses.
> >
> Hi Tony,
> 
> How are the clocks/power state currently handled in case of omap4_pmx_core,
> omap4_pmx_wkup register access via pinctrl-single ?

It's currently always on during runtime and managed in for the whole SCM
by mach-omap2/control.c. Then there's a separate SCM register that triggers
the save and restore of the padconf registers in hardware for off-idle
along with other SCM related things, see the *_control_save/restore_context()
functions.

Regards,

Tony
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