linux-kernel - Re: [PATCH RFC] mfd: syscon: Decouple syscon interface from syscon devices

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Date:	Thu, 19 Jun 2014 02:06:20 +0200
From:	Michal Simek <monstr@...str.eu>
To:	Arnd Bergmann <arnd@...db.de>, Tomasz Figa <tomasz.figa@...il.com>
CC:	linux-arm-kernel@...ts.infradead.org, mark.brown@...aro.org,
	Tomasz Figa <t.figa@...sung.com>,
	linux-samsung-soc@...r.kernel.org,
	Kukjin Kim <kgene.kim@...sung.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Samuel Ortiz <sameo@...ux.intel.com>,
	Pankaj Dubey <pankaj.dubey@...sung.com>,
	linux-kernel@...r.kernel.org, joshi@...sung.com,
	vikas.sajjan@...sung.com, chow.kim@...sung.com,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH RFC] mfd: syscon: Decouple syscon interface from syscon
 devices

Hi,

On 06/18/2014 02:57 PM, Arnd Bergmann wrote:
> On Tuesday 17 June 2014 23:26:22 Tomasz Figa wrote:
>> On 17.06.2014 17:42, Arnd Bergmann wrote:
>>> This seems like a reasonable way of solving the problem, but I think
>>> there is an even better one that we have about in the past: if we
>>> promote syscon from a platform driver into a a drivers/base/ helper
>>> that is independent of the platform device matching, we can use
>>> call syscon_regmap_lookup_* for any device node, whether it's already
>>> bound to a driver or not, which do what you need. It would also make
>>> it easier to call the syscon code before the platform_device
>>> infrastructure gets initialized, which is something a number of
>>> people have asked for, e.g. for using regmap to do SMP bringup
>>> or for clock registration.
>>
>> Basically, unless I'm missing your point, this is what my patch does,
>> except that I don't move it to drivers/base/ and the registration
>> function I added require a pointer to struct device. Indeed, decoupling
>> it further from the driver model, by adding of_syscon_register() should
>> be useful for early users.
> 
> I believe the part you are missing is that with the approach I suggested,
> there would be no registration function at all. You can easily do the
> lookup from the client drivers using the DT data structures, with no
> need for the device at all. The only exception today is the clps711x
> platform using syscon_regmap_lookup_by_pdevname(), but that should be
> solved in 3.17 when clps711x becomes DT-only.

I agree with Arnd. This patch is doing the part of what we wanted to do with it.
It means create a list of registered devices.
But you are working with struct device which you can't use in early phase
which is the feature we wanted to use. But currently we have workaround
in the kernel and clk subsystem is not able to work with regmap anyway.

Moving to proper location is just the last step.

Thanks,
Michal

-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Microblaze cpu - http://www.monstr.eu/fdt/
Maintainer of Linux kernel - Xilinx Zynq ARM architecture
Microblaze U-BOOT custodian and responsible for u-boot arm zynq platform



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