linux-kernel - Re: [PATCH 1/1] AArch64: TCR_TG1_64K incorrectly sets TCR

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Message-ID: <20140403085835.GC17022@arm.com>
Date:	Thu, 3 Apr 2014 09:58:35 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Joe Sylve <joe.sylve@...il.com>
Cc:	Will Deacon <Will.Deacon@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] AArch64: TCR_TG1_64K incorrectly sets TCR_EL1 bits
 [31:30]

On Wed, Apr 02, 2014 at 06:21:29PM +0100, Joe Sylve wrote:
> That makes sense and I agree, it's better to fix it now so that it
> will be easier to add 16K paging later (on a side note is there any
> reason not to add it now if someone was willing to do the work?).

See another thread with the Samsung folks about the adding 4-levels of
page tables. We need a bit of refactoring first to decouple the page
size from the number of levels, after that 16K would be relatively easy
(it's easy now as well but I don't see the point on doing it before the
refactoring).

> There was talk in another thread about the possibility of adding a
> pagetable-4K-hwdef.h and pagetable-64K-hwdef.h.  I think this is
> another example of why that might be a good idea as this stuff could
> be moved out of proc.S as to be bit more clean:
> 
> +#ifdef CONFIG_ARM64_64K_PAGES
> +#define TCR_TG_FLAGS   TCR_TG0_64K | TCR_TG1_64K
> +#else
> +#define TCR_TG_FLAGS   TCR_TG0_4K | TCR_TG1_4K
> +#endif

Yes, we could do this when we create the pgtable-*k-hwdef.h files.

-- 
Catalin
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