linux-kernel - Re: [GIT PULL] ARM fixes

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Date:	Tue, 18 Feb 2014 16:23:51 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	James Bottomley <James.Bottomley@...allels.com>,
	Linux SCSI List <linux-scsi@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	ARM SoC <arm@...nel.org>, xen-devel@...ts.xenproject.org
Subject: Re: [GIT PULL] ARM fixes

On Tue, Feb 18, 2014 at 4:03 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
>
> Almost, but not quite.  If we're going to avoid u64, then dma_addr_t
> woudl be the right type here because we're talking about DMA addresses.

Well, phys_addr_t had better be as big as dma_addr_t, because that's
what the resource management handles.

> We could also switch to keeping this as PFNs - block internally converts
> it to a PFN anyway:

Yeah, that definitely sounds like it would be a good idea.

> Maybe blk_queue_bounce_pfn_limit() so we ensure all users get caught?
>
>> That said, it's admittedly a disgusting name, and I wonder if we
>> should introduce a nicer-named "pfn_to_phys()" that matches the other
>> "xyz_to_abc()" functions we have (including "pfn_to_virt()")
>
> We have these on ARM:
>
> arch/arm/include/asm/memory.h:#define   __pfn_to_phys(pfn)      ((phys_addr_t)(pfn) << PAGE_SHIFT)
> arch/arm/include/asm/memory.h:#define   __phys_to_pfn(paddr)    ((unsigned long)((paddr) >> PAGE_SHIFT))
>
> it probably makes sense to pick those right out, maybe losing the
> __ prefix on them.

Yup.

>>   __va(PFN_PHYS(page_to_pfn(page)));
>
> Wow.  Two things spring to mind there... highmem pages, and don't we
> already have page_address() for that?

Well, that code clearly cannot handle highmem anyway, but yes, it
really smells like xen should use page_address().

Adding Xen people who I didn't add the last time around.

             Linus
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