linux-kernel - Re: [GIT PULL] arch/microblaze fixes for 2.6.35-rc3 v2

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Message-Id: <20100608200201I.fujita.tomonori@lab.ntt.co.jp>
Date:	Tue, 8 Jun 2010 20:03:15 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	michal.simek@...alogix.com
Cc:	fujita.tomonori@....ntt.co.jp, linux-kernel@...r.kernel.org
Subject: Re: [GIT PULL] arch/microblaze fixes for 2.6.35-rc3 v2

On Tue, 08 Jun 2010 12:28:53 +0200
Michal Simek <michal.simek@...alogix.com> wrote:

> FUJITA Tomonori wrote:
> > On Mon, 07 Jun 2010 20:20:03 +0200
> > Michal Simek <michal.simek@...alogix.com> wrote:
> > 
> >> Hi Linus,
> >>
> >> here are only fixes for Microblaze. There is no any new features. 
> >> (flush_dcache_page patch fix problem on WB system)
> >> Just note: Some new patches broke Microblaze arch that's why I would 
> >> like to add at least these patches to your tree.
> >>
> >> Thanks,
> >> Michal
> >>
> >>
> >> The following changes since commit 386f40c86d6c8d5b717ef20620af1a750d0dacb4:
> >>    Linus Torvalds (1):
> >>          Revert "tty: fix a little bug in scrup, vt.c"
> >>
> >> are available in the git repository at:
> >>
> >>    git://git.monstr.eu/linux-2.6-microblaze.git next
> >>
> >> Michal Simek (7):
> >>        microblaze: Fix __copy_to/from_user_inatomic macros
> >>        microblaze: Sync noMMU and MMU setup_memory
> >>        microblaze: Fix comment for TLB
> >>        microblaze: Implement flush_dcache_page macro
> >>        microblaze: Enable NEED_SG_DMA_LENGTH
> > 
> > Sorry, my scatterlist patchset breaks microblaze?
> 
> yes, it does.
> http://www.monstr.eu/wiki/doku.php?id=log:2010-06-07_12_23_12#folded_17

Sorry about that.


> > Seems that microblaze can simply remove sg->dma_length instead of
> > enabling NEED_SG_DMA_LENGTH. If sg->dma_length is always equal to
> > sg->length on your architecture, you don't need to waste memory for
> > sg->dma_length.
> 
> Please correct me if I am wrong. dma_length is used for 64bit machines.

dma_length is used for 32bit machines too.

dma_length is necessary if sg->dma_length can be different to
sg->length, that is, some IOMMU implementations merge several sg
entries to one sg entry.

There are not many 32bit architectures that support an IOMMU so
NEED_SG_DMA_LENGTH is usually used on 64bit archs though.


> Microblaze is "only" 32bit.
> 
> Can you please generate proper patch?

Sure. With this patch, you don't need to enable NEED_SG_DMA_LENGTH.

=
From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Subject: [PATCH] microblaze: fix sg_dma_len() regression

The commit 8e98307de0d746cb0845ebf66535ce2184c25a2 broke microblaze.

dma_direct_map_sg() sets sg->dma_length, however microblaze doesn't
set NEED_SG_DMA_LENGTH so scatterlist strcutres doesn't include
dma_length.

sg->dma_length is always equal to sg->length on microblaze. So we
don't need to set set dma_length, that is, microblaze can simply use
sg->length.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
---
 arch/microblaze/kernel/dma.c |    1 -
 1 files changed, 0 insertions(+), 1 deletions(-)

diff --git a/arch/microblaze/kernel/dma.c b/arch/microblaze/kernel/dma.c
index 9dcd90b..79c7465 100644
--- a/arch/microblaze/kernel/dma.c
+++ b/arch/microblaze/kernel/dma.c
@@ -90,7 +90,6 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
 	/* FIXME this part of code is untested */
 	for_each_sg(sgl, sg, nents, i) {
 		sg->dma_address = sg_phys(sg) + get_dma_direct_offset(dev);
-		sg->dma_length = sg->length;
 		__dma_sync_page(page_to_phys(sg_page(sg)), sg->offset,
 							sg->length, direction);
 	}
-- 
1.6.5

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