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

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Date:	Mon, 19 Oct 2015 11:25:49 +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

Thomas,

2015-10-19 9:23 GMT+02:00 Thomas Petazzoni
<thomas.petazzoni@...e-electrons.com>:
> Hello,
>
> On Mon, 19 Oct 2015 08:04:49 +0200, Marcin Wojtas wrote:
>
>> > 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...
>
> The current driver is indeed not designed for multiple instances of the
> same pinctrl controller. But that's exactly what Russell is asking for.
>

In each mvebu pinctl there are <soc>_mpp_ctrl_get/set force usage of
global mpp_base. In order not to use it this way the functions have to
be redesigned. IMO having an acces to pdev would be sufficient (please
see my proposal below), but yet I don't have a clear idea, how to do
it,

>> 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 {
>
> This definitely shouldn't be called "pm_info", because 'base' is not PM
> related. It should be mvebu_pinctrl_state or something like that.
>
>>     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;
>
> Does not work because "mvebu_pinctrl_pm_info" cannot be a generic
> structure, it has to be a per-SoC driver structure, since the set of
> registers to save for PM reasons is different from one SoC to the
> other. Also, some SoC have only one "base" pointer, some others (like
> Dove) have multiple.
>
> So it should be the other way around: the SoC-specific driver create a
> structure, and this structure points back to the mvebu_pinctrl
> structure.
>

How about a following compromise:
Instead of forcing pm_info, we can add a generic pointer to struct
mvebu_pinctrl, e.g. void *priv; and enable passing it in a way I
proposed before.

This way each SoC-specific driver can attach whatever is needed for
its operation. For example in A38X/AXP it would be *base,
*mpp_saved_regs and nregs gathered in one structure, but it wouldn't
force anything specific for other machines. As a result in A38X/AXP in
suspend/resume routines, there would be no globals in use at all.

Best regards,
Marcin
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