linux-kernel - Re: [PATCH v7 3/4] ARM: EXYNOS: Add platform driver support for Exynos PMU

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Message-ID: <53F61754.6010206@gmail.com>
Date:	Thu, 21 Aug 2014 17:59:16 +0200
From:	Tomasz Figa <tomasz.figa@...il.com>
To:	Pankaj Dubey <pankaj.dubey@...sung.com>,
	'Bartlomiej Zolnierkiewicz' <b.zolnierkie@...sung.com>,
	'Arnd Bergmann' <arnd@...db.de>,
	'Lee Jones' <lee.jones@...aro.org>
CC:	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux@....linux.org.uk, t.figa@...sung.com,
	vikas.sajjan@...sung.com, joshi@...sung.com, naushad@...sung.com,
	thomas.ab@...sung.com, chow.kim@...sung.com,
	'Kukjin Kim' <kgene.kim@...sung.com>,
	PRASHANTH GODREHAL <prashanth.g@...sung.com>
Subject: Re: [PATCH v7 3/4] ARM: EXYNOS: Add platform driver support for Exynos
 PMU

On 21.08.2014 16:07, Pankaj Dubey wrote:
> +Arnd, Lee Jones
> 
> Hi Tomasz,
> 
> On Tuesday, August 19, 2014 Tomasz Figa wrote:
> 
>>
>> Hi Bart,
>>
>> On 18.08.2014 19:42, Bartlomiej Zolnierkiewicz wrote:
>>>
>>> Hi,
>>>
>>> On Monday, July 28, 2014 08:40:52 AM Pankaj Dubey wrote:
>>>> Hi Tomasz,
>>>>
>>>> On Friday, July 25, 2014 Tomasz Figa wrote:
>>>>
>>>>> To: Pankaj Dubey; 'Kukjin Kim';
>>>>> linux-arm-kernel@...ts.infradead.org;
>>>> linux-
>>>>> samsung-soc@...r.kernel.org; linux-kernel@...r.kernel.org
>>>>> Cc: linux@....linux.org.uk; t.figa@...sung.com;
>>>>> vikas.sajjan@...sung.com; joshi@...sung.com; naushad@...sung.com;
>>>>> thomas.ab@...sung.com; chow.kim@...sung.com
>>>>> Subject: Re: [PATCH v7 3/4] ARM: EXYNOS: Add platform driver support
>>>>> for Exynos PMU
>>>>>
>>>>> Hi Pankaj, Kukjin,
>>>>>
>>>>> On 25.07.2014 07:32, Pankaj Dubey wrote:
>>>>>> Hi Kukjin,
>>>>>>
>>>>>> On Friday, July 25, 2014 Kukjin Kim wrote:
>>>>>
>>>>> [snip]
>>>>>
>>>>>>>>
>>>>>>> Looks good to me, will apply this and 4/4.
>>>>>>>
>>>>>>
>>>>>> We need to hold these two patches until dependent patch [1] from
>>>>>> Tomasz Figa gets merged.
>>>>>>
>>>>>> [1]: mfd: syscon: Decouple syscon interface from syscon devices
>>>>>>       https://lkml.org/lkml/2014/6/24/188
>>>>>
>>>>> That RFC patch had few comments from Arnd needed to be addressed, so
>>>>> it
>>>> needs a
>>>>> new revision.
>>>>>
>>>>> Pankaj, If I remember correctly, we had talked about this and the
>>>> conclusion was that
>>>>> you would take care of addressing the comments and sending new
>>>>> version of
>>>> the
>>>>> patch. Any update on this or have I missed something?
>>>>>
>>>>
>>>> Well, I don't think we concluded as such anything.
>>>> Since this patch needs to get in so that Exynos PMU and PM related
>>>> changes can go in, I discussed with you saying that I am not able to
>>>> understand about Arnd's comments and if possible and time permits I
>>>> will look into it. Meanwhile I got busy with some other official
>>>> work, so could not get time to look into it.
>>>
>>> Tomasz/Pankaj, could we please get some agreement on what needs to be
>>> done and who should do the pending work?
>>>
>>> syscon patch is blocking PMU cleanup patches which in turn are
>>> blocking PMU support additions for new SoCs (Exynos5420/5800 and
>>> Exynos3250 PMU patches).
>>
>> Leaving alone the matter who is going to take care of it for now, the
> remaining work
>> to do is to further decouple syscon from struct device, which means
> providing of_
>> API to register a syscon provider on a device tree node even before driver
> model is
>> available yet.
>>
> 
> As per Arnd's comment on your RFC patch he mentioned -
> "I believe the part you are missing is that with the approach I suggested,
> there would be no registration function at all."
> 
> I think he is not in favor of adding such registration function at all. So
> do you think
> adding such function will really solve the problem?
> 
> Further even Lee Jones agreed to Arnd's point of making syscon independent
> of device,
> but he also mentioned that it can be done in subsequent patch.

Let's look again at the original thread then...

I believe Lee agreed with my proposed solution or at least he quoted my
e-mail and pointed that further work addressing Arnd's comments could be
done in follow up patches. I also think that we should rather make one
step as a time, especially this patch is required for further clean-up
of Exynos.

However there was also a reply from Michal Simek, which pointed out that
even with my patch the syscon is still bound to driver model and for his
use case he would need a purely OF-based version of the API. That's why
I think my patch should be re-spun with changes I mentioned in my
previous message in this thread.

>   
> So in IMHO, your RFC patch can be taken as is, and any further improvement
> suggested
> by Arnd can be done in subsequent patches,  because as I can see in 3.17-rc1
> still
> has user of syscon_regmap_lookup_by_pdevname (clps711x.c) so we can't
> completely
> make it independent of platform_device as of now and also the changes
> required
> as per Arnd's suggestions requires considerable effort and time.

Agreed. However we can still provide OF-only syscon registration
function and modify look-up functions to allow syscons without struct
device pointer, just with OF node.

Best regards,
Tomasz
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