linux-kernel - Re: [PATCH] pinctrl: mvebu: armada-38x: add suspend/resume support

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Date:	Mon, 19 Oct 2015 08:04:49 +0200
From:	Marcin Wojtas <mw@...ihalf.com>
To:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Andrew Lunn <andrew@...n.ch>,
	Jason Cooper <jason@...edaemon.net>,
	Tawfik Bayouk <tawfik@...vell.com>,
	Grzegorz Jaszczyk <jaz@...ihalf.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-kernel@...r.kernel.org, nadavh@...vell.com,
	linux-gpio@...r.kernel.org, Lior Amsalem <alior@...vell.com>,
	Gregory Clément 
	<gregory.clement@...e-electrons.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>
Subject: Re: [PATCH] pinctrl: mvebu: armada-38x: add suspend/resume support

Hi Thomas,

2015-10-18 16:01 GMT+02:00 Thomas Petazzoni
<thomas.petazzoni@...e-electrons.com>:
> Hello Marcin,
>
> On Sun, 18 Oct 2015 10:43:42 +0200, Marcin Wojtas wrote:
>
>> Thanks for pointing this. I based on pinctrl-armada-xp.c (it needs a
>> fix then, too) and it worked. I must have missed, because I got proper
>> registers' number and values in suspend/resume routines. As
>> pinctrl-armada-xp.c needs also a small fix and in order not to
>> duplicate code, how about a following solution:
>> - *mpp_saved_regs and *mpp_base become members of struct mvebu_pinctrl_soc_info
>
> I don't like this. The mvebu_pinctrl_soc_info structure is meant to be
> a read-only structure that only describes static information giving
> SoC-specific details for pin-muxing. The idea is that in the event
> where you had multiple pinctrl in the same system, you would still have
> only one instance of mvebu_pinctrl_soc_info.

Ok, understood. What with current static globals, like mpp_base? This
is a problem when we consider hypothetical multi-pintrl system...

>
> So, I'd prefer if mpp_saved_regs and mpp_base became members of a new
> structure, that gets allocated at ->probe() time, on a per-instance
> basis.
>
>> - common mvebu_pinctrl_suspend/resume functions in pinctrl-mvebu.c
>> (now there will be two users AXP and A38X)
>
> Not sure how to handle that if the per-instance structure is defined on
> a per-SoC basis, but I'm interested in seeing proposals.
>

In genereal, I think storing additional global data is not
starightforward, as dev->platform_data and dev->driver_data are
currently occupied by mvebu_pinctrl and mvebu_pinctrl_soc_info. I
propose the following:

1. Create a new structure:
struct mvebu_pinctrl_pm_info {
    void __iomem *base;
    static u32 *mpp_saved_regs;
    int nregs;
}

2. Add new field to struct mvebu_pinctrl:
struct mvebu_pinctrl_pm_info *pm_info;

3. In armada_38x/xp_pinctrl_probe we do the allocations and pass
struct pm_info using dev->driver data (later in mvebu_pinctrl_probe it
will be replaced by struct mvebu_pinctrl):
platform_set_drvdata(pdev, pm_info);

return mvebu_pinctrl_probe(pdev);

4. In mvebu_pinctrl_probe:
struct mvebu_pinctrl_pm_info *pm_info = platform_get_drvdata(pdev);
(...)

if (pm_info)
    pctl->pm_info = pm_info;
platform_set_drvdata(pdev, pctl);

5. Now, we can simply use all stored data in common
mvebu_pinctrl_suspend/resume.

I hope the above is clear. I'm looking forward to your opinion.

Beste regards,
Marcin
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