linux-kernel - Re: [PATCH v2 4/6] ARM: firmware: add prepare

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Date:	Fri, 14 Feb 2014 11:42:50 +0100
From:	Tomasz Figa <t.figa@...sung.com>
To:	Alexandre Courbot <acourbot@...dia.com>,
	Stephen Warren <swarren@...dotorg.org>,
	Thierry Reding <thierry.reding@...il.com>,
	Russell King <linux@....linux.org.uk>
Cc:	Olof Johansson <olof@...om.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"gnurou@...il.com" <gnurou@...il.com>
Subject: Re: [PATCH v2 4/6] ARM: firmware: add prepare_idle() operation

On 14.02.2014 06:16, Alexandre Courbot wrote:
> On 02/13/2014 08:01 PM, Tomasz Figa wrote:
>> Hi Alexandre,
>>
>> On 07.02.2014 05:35, Alexandre Courbot wrote:
>>> Some firmwares do not put the CPU into idle mode themselves, but still
>>> need to be informed that the CPU is about to enter idle mode before this
>>> happens. Add a prepare_idle() operation to the firmware_ops structure to
>>> handle such cases.
>>>
>>> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
>>> ---
>>>    arch/arm/include/asm/firmware.h | 4 ++++
>>>    1 file changed, 4 insertions(+)
>>
>> I wonder if .do_idle() couldn't simply return an appropriate error code
>> to let the upper layer know that it should proceed with normal CPU idle
>> activation, while still letting the firmware know that the CPU is going
>> to idle.
>
> In our particular case I agree it would be enough to use do_idle() to
> let the firmware know about the operation and have it return -ENOSYS so
> the kernel actually performs it. I'm afraid this might not fulfill all
> needs though (e.g. one can imagine a firmware where the OS needs to take
> action between the notification and the actual shutdown), and as Stephen
> pointed out that would make the name of the function ambiguous at best.
> I'd rather keep it the current way for clarity.
>

OK. I'm not strongly against this, just wanted some more thought on 
this, so please move on.

Best regards,
Tomasz
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