[Top] [All Lists]

Re: [PATCH] linux-next remove wmb() from ide-dma-sff.c and scc_pata.c

Subject: Re: [PATCH] linux-next remove wmb() from ide-dma-sff.c and scc_pata.c
From: Atsushi Nemoto <>
Date: Wed, 01 Apr 2009 00:26:51 +0900 (JST)
In-reply-to: <>
Original-recipient: rfc822;
References: <> <>
On Tue, 31 Mar 2009 09:51:53 +0200 (CEST), Geert Uytterhoeven 
<> wrote:
> > Followup to "[PATCH 03/10] ide: destroy DMA mappings after ending DMA"
> > email on March 14th:
> >
> > 
> > No maintainer is listed for "Toshiba CELL Reference Set IDE" 
> > or tx4939ide.c in MAINTAINERS. I've CC'd "Ishizaki Kou" @Toshiba 
> > (Maintainer for
> > "Spidernet Network Driver for CELL") and linuxppc-dev list in the hope
> > someone else
> > would know or would be able to ACK this patch.
> tx49xx is MIPS, for Nemoto-san.
> > This patch:
> > o replaces "mask" variable in ide_dma_end() with #define.
> > o removes use of wmb() in ide-dma-sff.c and scc_pata.c.
> > o is not tested - I don't have (or want) the HW.
> > 
> > I did NOT remove wmb() use in tx4939ide.c. tx4939ide.c __raw_writeb()
> > for MMIO transactions. __raw_writeb() does NOT guarantee memory
> > transaction ordering.

The wmb() in tx4939ide.c was just copied from ide_dma_end().  On this
MIPS core memory operations are strictly ordered so that the wmb() can
be removed.

And on MIPS __raw_writeb() and writeb() do same thing except for
endian conversion.

I will send a patch just for tx4939ide.c.  Thank you for suggestion.

> > tx4939ide also uses mmiowb(). AFAIK, mmiowb() only has an effect on
> > SGI IA64 NUMA machines. I'm not going to guess how this driver might work.

On MIPS mmiowb() can be (ab)used to flush write buffer.  Please do not
drop this mmiowb().

Atsushi Nemoto

<Prev in Thread] Current Thread [Next in Thread>