linux-kernel - Re: [STLinux Kernel] [PATCH 1/3] media: st-rc: move to using reset_control_get_optional

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Message-ID: <542282E3.8080102@st.com>
Date:	Wed, 24 Sep 2014 10:37:55 +0200
From:	Maxime Coquelin <maxime.coquelin@...com>
To:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Peter Griffin <peter.griffin@...aro.org>
Cc:	<linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
	<kernel@...inux.com>, <linux-arm-kernel@...ts.infradead.org>,
	Mauro Carvalho Chehab <m.chehab@...sung.com>
Subject: Re: [STLinux Kernel] [PATCH 1/3] media: st-rc: move to using reset_control_get_optional

Hi Srini, Peter,

On 09/24/2014 10:12 AM, Srinivas Kandagatla wrote:
> Hi Pete,
> 
> On 23/09/14 19:02, Peter Griffin wrote:
>> Hi Srini,
>>
>> On Mon, 22 Sep 2014, Srinivas Kandagatla wrote:
>>
>>> This patch fixes a compilation error while building with the
>>> random kernel configuration.
>>>
>>> drivers/media/rc/st_rc.c: In function 'st_rc_probe':
>>> drivers/media/rc/st_rc.c:281:2: error: implicit declaration of
>>> function 'reset_control_get' [-Werror=implicit-function-declaration]
>>>    rc_dev->rstc = reset_control_get(dev, NULL);
>>>
>>> drivers/media/rc/st_rc.c:281:15: warning: assignment makes pointer
>>> from integer without a cast [enabled by default]
>>>    rc_dev->rstc = reset_control_get(dev, NULL);
>>
>> Is managing the reset line actually optional though? I can't test atm 
>> as I don't have
>> access to my board, but quite often if the IP's aren't taken out of 
>> reset reads / writes
>> to the perhpiheral will hang the SoC.
>>
> Yes and No.
> AFAIK reset line is optional on SOCs like 7108, 7141.
> I think having the driver function without reset might is a value add in 
> case we plan to reuse the mainline driver for these SOCs.
> 
> On latest ARM SOCs with SBC the IRB IP is moved to SBC and held in reset.
> Am not sure, if the reset line is optional in next generation SOCs?

I don't know for next SoCs, but I think it makes sense to make it optional.

Regards,
Maxime

> 
>> If managing the reset line isn't optional then I think the correct fix 
>> is to add
>> depends on RESET_CONTROLLER in the kconfig.
> I agree.
> This would make the COMPILE_TEST less useful though.
> 
> 
> thanks,
> srini
>>
>> This will then do the right thing for randconfig builds as well.
>>
>> regards,
>>
>> Peter.
>>
> 
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