linux-kernel - Re: Regression (ARM) arch/arm/mm/init.c doesn't build without CONFIG_ARM_PATCH_PHYS

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Message-ID: <20140107175505.GK27432@n2100.arm.linux.org.uk>
Date:	Tue, 7 Jan 2014 17:55:06 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Santosh Shilimkar <santosh.shilimkar@...com>
Cc:	Krzysztof Hałasa <khalasa@...p.pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: Regression (ARM) arch/arm/mm/init.c doesn't build without
	CONFIG_ARM_PATCH_PHYS_VIRT.

On Tue, Jan 07, 2014 at 12:45:42PM -0500, Santosh Shilimkar wrote:
> On Monday 06 January 2014 08:11 PM, Russell King - ARM Linux wrote:
> > /--------------------------------------------------------------
> > | > > Right, so, with Assabet, which has CONFIG_DMA_ZONE=y and
> > | > > CONFIG_ARM_PATCH_PHYS_VIRT=y:
> > | > > 
> > | > > $ make O=../build/assabet arch/arm/mm/init.i
> > | > > 
> > | > > gives:
> > | > >   arm_dma_limit = __pv_phys_offset + arm_dma_zone_size - 1;
> > | > > 
> > | > > with or without Santosh's patch.
> > \--------------------------------------------------------------
> > 
> >> May be I missed your point but I ended up creating the patch because
> >> the CMA reservation was failing on Keystone since the arm_dma_limit
> >> wasn't right since it wasn't considering the actual __pv_phys_offset.
> >>
> >> Isn't that an issue ?
> > 
> > See the above.  Your patch has _no_ effect what so ever when
> > CONFIG_ARM_PATCH_PHYS_VIRT=y - which you have on the Keystone, right?
> > 
> > If you don't believe me, ask make to produce arch/arm/mm/init.i, which
> > is the output from the preprocessor, comparing the resulting generated
> > file both with and without your patch applied.
> > 
> Looks like you are right. I did two fixes to have right arm_dma_limit in
> below order.
> 
> 1. 787b0d5 {ARM: 7908/1: mm: Fix the arm_dma_limit calculation}
> 2. 7c92732 {ARM: 7909/1: mm: Call setup_dma_zone() post early_paging_init()}
> 
> But with 2 alone the issue gets fixed since with ARM_PATCH_PHYS_VIRT and
> below pre-processor, the PHYS_OFFSET also gets an updated value. I never
> realised that 1 becomes redundant after second patch while creating them. 
> 
> #define PHYS_OFFSET __pv_phys_offset
> 
> So indeed, 787b0d5{ARM: 7908/1: mm: Fix the arm_dma_limit calculation}
> won't be needed anymore and can be reverted. Sorry it took some time
> for me to reach to your conclusion.

Okay, reverted.

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