[U-Boot] [PATCH] blk: Remove various places that do flush cache after read

Y.b. Lu yangbo.lu at nxp.com
Thu Aug 24 03:54:42 UTC 2017

> -----Original Message-----
> From: Bin Meng [mailto:bmeng.cn at gmail.com]
> Sent: Wednesday, August 23, 2017 1:29 PM
> To: Y.b. Lu
> Cc: Qiang Zhao; York Sun; Grygorii Strashko; Michal Simek; Angelo
> Dureghello; Kever Yang; Jaehoon Chung; Albert Aribaud; Marcel Ziswiler;
> Markus Niebel; Z.q. Hou; Sumit Garg; Joe Hershberger; Stefan Roese;
> Wenbin Song; Simon Glass; Max Krummenacher; Masahiro Yamada; Tomas Melin;
> Q.y. Gong; Tom Rini; U-Boot Mailing List
> Subject: Re: [PATCH] blk: Remove various places that do flush cache after
> read
> Hi Yangbo,
> On Wed, Aug 23, 2017 at 11:29 AM, Y.b. Lu <yangbo.lu at nxp.com> wrote:
> > cmd/mmc.c
> >
> > Maybe SD controller on some vendor platforms doesn't support SNOOP.
> > flush_cache() is required to sync between DDR and cache.
> > Should be careful to remove this.
> >
> Please do not top-posting.
> What you mentioned if snoop is not supported, flush_cache() is required,
> is true, however that's not the issue I am trying to fix here. The
> flush_cache() here after a DMA read will cause issues because stale data
> in the cache will overwrite the correct data in the RAM that is DMAed by
> hardware (in this case, MMC controller).

[Lu Yangbo-B47093] Sorry for my misunderstanding. It looks ok to me now.
flush_cache is indeed redundant after DMA reading.

> Regards,
> Bin

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