linux-kernel - Re: [PATCH] ARM: cache-l2x0.c: save aux ctrl for resume in case that l2x0 is enabled before init

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Date:	Thu, 26 Apr 2012 17:25:31 +0800
From:	Yilu Mao <ylmao@...vell.com>
To:	Catalin Marinas <catalin.marinas@....com>
CC:	Lu Mao <ylmao@...vell.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"Baohua.Song@....com" <Baohua.Song@....com>,
	"santosh.shilimkar@...com" <santosh.shilimkar@...com>,
	"robherring2@...il.com" <robherring2@...il.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: cache-l2x0.c: save aux ctrl for resume in case that
 l2x0 is enabled before init

On 04/26/2012 04:35 PM, Catalin Marinas wrote:
> On Thu, Apr 26, 2012 at 06:00:09AM +0100, Yilu Mao wrote:
>> On 04/24/2012 04:28 PM, Catalin Marinas wrote:
>>> On Tue, Apr 24, 2012 at 03:41:20AM +0100, Yilu Mao wrote:
>>>> +	l2x0_saved_regs.aux_ctrl = aux;
>>>> +
>>>>    	aux&= aux_mask;
>>>>    	aux |= aux_val;
>>>
>>> I think that's the wrong place to save it, it should be after the
>>> masking was done.
>>>
>>> Anyway, if we cannot write this register in l2x0_init() because the L2
>>> was enabled, do we expect the L2 to be disabled during resume?
>>>
>> Sorry, I don't think so.
>> This is the right place to save it because we must make sure the saved
>> aux_ctrl is the same as what it is set.
>> If we save it after masking was done, the saved value will be different
>> because we can't actually change the real setting.
>
> And since we can't actually change the real setting on the resume path,
> why do we need to save it anyway. Is your L2 cache disabled on the
> resume path but not on the cold boot one?
>
We can't change L2 aux ctrl setting when do init because it has been 
enabled. But we have the requirement to handle core idle. For CA9 core 
idle, L2 controller may be reset. So we need to restore the L2 
controller registers base on l2x0_saved_regs. This is why we need to 
keep the value in l2x0_saved_regs to be the same as real setting.

-- 
Thanks.

Best Wishes,
Yilu Mao
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