linux-kernel - Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma

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Message-ID: <20130726151021.GU24642@n2100.arm.linux.org.uk>
Date:	Fri, 26 Jul 2013 16:10:21 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Tejun Heo <tj@...nel.org>, Jens Axboe <axboe@...nel.dk>,
	linux-scsi@...r.kernel.org
Subject: Re: [RFC/RFT PATCH 0/5] mm: ARM nobootmem and few dma_mask fixes

On Fri, Jul 12, 2013 at 05:48:09PM -0400, Santosh Shilimkar wrote:
> The series is an attempt to move ARM port to NO_BOOTMEM. As discussed
> on list NO_BOOTMEM move needed updates to max*pfn meaning to be maximum
> PFNs but that breaks the dma_mask for few block layer drivers since
> ARM start of physical memory is not PFN0 unlike most of the architectures.
> Some more read on it is here:
> 	http://lwn.net/Articles/543408/
> 	http://lwn.net/Articles/543424/
> 
> To address this issue, we introduce generic dma_max_pfn() helper which
> can be overridden from the architectures.
> 	
> Another intention behind move to nobootmem is also to convert ARM to
> switch to memblock and getting rid of bootmem allocator dependency which
> don't work for LPAE machines which has physical memory starting beyond
> 4 GB boundary. It needs changes to core kernel and also a new memblock
> API. More on this can be found here:
> 	https://lkml.org/lkml/2013/6/29/77
> 
> I have been trying to cook up these patches with kind help from Russell
> and we know series don't solve all the dma_mask bad assumptions. But at
> least I am hoping that it can get the ball rolling.	
> 
> Comments/testing help is welcome !!

As this is related to some of the cleanup of dma_mask which I've been
doing, I think it may make sense to roll this into one tree.  Any
objection to that?

Can we get any acks on this stuff from Jens and Jejb etc - especially
for the bits which touch block/ and for the scsi bits as these are
touching other subsystems.  (oddly, linux-scsi wasn't on the original
mail for this series summary.)
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