linux-kernel - Re: [PATCH] arm64: allow late use of early

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Date:	Wed, 14 Jan 2015 16:22:08 +0800
From:	Hanjun Guo <hanjun.guo@...aro.org>
To:	Mark Salter <msalter@...hat.com>, Will Deacon <will.deacon@....com>
CC:	Leif Lindholm <leif.lindholm@...aro.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: Re: [PATCH] arm64: allow late use of early_ioremap

Hi Mark,

On 2015年01月13日 03:09, Mark Salter wrote:
> On Mon, 2015-01-12 at 17:25 +0000, Will Deacon wrote:
>> On Mon, Jan 12, 2015 at 04:55:11PM +0000, Mark Salter wrote:
>>> Commit 0e63ea48b4d8 (arm64/efi: add missing call to early_ioremap_reset())
>>> added a missing call to early_ioremap_reset(). This triggers a BUG if code
>>> tries using early_ioremap() after the early_ioremap_reset(). This is a
>>> problem for some ACPI code which needs short-lived temporary mappings
>>> after paging_init() but before mm_init(). This patch adds definitions for

Minor update:
... after paging_init() but before acpi_early_init() in start_kernel().

In ACPI, permanent mapping will be used after acpi_gbl_permanent_mmap
set to 1 in acpi_early_init(), since GIC init and Arch timer init will
be called before acpi_early_init(), early_ioremap() is still needed
after mm_init().

>>> the __late_set_fixmap() and __late_clear_fixmap() which avoids the BUG
>>> by allowing later use of early_ioremap().
>>>
>>> Signed-off-by: Mark Salter <msalter@...hat.com>
>>> CC: Leif Lindholm <leif.lindholm@...aro.org>
>>> CC: Ard Biesheuvel <ard.biesheuvel@...aro.org>
>>> ---
>>>   arch/arm64/include/asm/fixmap.h | 3 +++
>>>   1 file changed, 3 insertions(+)
>>
>> Given that we don't support ACPI on arm64 in mainline, I assume this can
>> wait until at least 3.20?
>
> Sure. Just needs it to go in before ACPI code. And tbh, the ACPI code
> could change and make this unneeded.

This is the best solution for now, so I need to add this patch as the 
first one for ACPI core patch set, is it ok for you?

Thanks
Hanjun
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