linux-kernel - Re: [PATCH v4 06/11] ARM: EXYNOS: Add support for mapping PMU base address via DT

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Date:	Tue, 17 Jun 2014 17:26:37 +0200
From:	Tomasz Figa <t.figa@...sung.com>
To:	Pankaj Dubey <pankaj.dubey@...sung.com>,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Cc:	kgene.kim@...sung.com, linux@....linux.org.uk,
	chow.kim@...sung.com, vikas.sajjan@...sung.com, joshi@...sung.com
Subject: Re: [PATCH v4 06/11] ARM: EXYNOS: Add support for mapping PMU base
 address via DT

Hi Pankaj,

On 17.06.2014 08:43, Pankaj Dubey wrote:
> Hi Tomasz,
> 
>> Hi,
>>
>> On 10.05.2014 08:56, Pankaj Dubey wrote:
>>> From: Young-Gun Jang <yg1004.jang@...sung.com>
>>>
>>> Add support for mapping Samsung Power Management Unit (PMU) base
>>> address from device tree. This patch also adds helper function as
>>> "get_exynos_pmuregmap". This function can be used by other machine
>>> files such as "pm.c", "hotplug.c" for accessing PMU regmap handle.
>>>
>>
>> I don't think there is a need to use regmap to provide access to PMU to
> such low
>> level code such as pm.c or hotplug.c. Moreover, I believe that it might be
> undesirable
>> in some cases, e.g. very low level code running at early resume or late
> suspend.
>>
>> IMHO, based on what we now have for SYSRAM, you could simply map PMU from
>> device tree one time, before SMP init, and keep the address in some
> globally
>> accessible variable, like those for SYSRAM we have right now
> (sysram_base_addr,
>> sysram_ns_base_addr -> pmu_base_addr).
>>
> 
> Thanks for review. 
> 
> Well I adopted same approach in V1 of this patch series. 
> 
> V1: https://lkml.org/lkml/2014/4/2/48
> 
> So, if we do not have issues with that approach, I think we can map PMU
> address
> one time and use it for all machine files including pmu.c. 

The approach itself is fine, but I believe there is no reason to use fdt
there. My recommendation is to follow the method used to map SYSRAMs in
patch "b3205dea8f ARM: EXYNOS: Map SYSRAM through generic DT bindings"
and taking into account patch "b87abf7deb ARM: exynos: move sysram info
to exynos.c", which moves things around source files.

> Also I can see that early_syscon patch [1] is not progressing anymore,
> so in next version of this series better I remove dependency of early syscon
> and usage
> of regmap.

I have another proposal, basically something I already proposed in
review of one of previous versions of this series. I will send a patch
as a reply to this message.

> 
> 1: https://lkml.org/lkml/2014/4/8/239
> 
> Tomasz, It will be good if you can review remaining patches under this
> series, specially patch [2].
> So that, I can update this series after addressing all comments.
> 
> 2: https://lkml.org/lkml/2014/5/10/26
> 

Most of the patches have already received my reviewed-by tag. I'm
generally hesitating to review remaining ones, because the general
architecture will be quite different after changing things mentioned
above. However let me see and try to point issues I can find.

Best regards,
Tomasz
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