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From: Bin Meng <bmeng.cn@gmail.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [PATCH] blk: Remove various places that do flush cache after read
Date: Wed, 23 Aug 2017 13:28:35 +0800	[thread overview]
Message-ID: <CAEUhbmVFDTao=4qYghGWdTihFxieNtPO4PUnQcXT_7WrQCoHHQ@mail.gmail.com> (raw)
In-Reply-To: <DB6PR0401MB25362F40E1973E968FE001FFF8850@DB6PR0401MB2536.eurprd04.prod.outlook.com>

Hi Yangbo,

On Wed, Aug 23, 2017 at 11:29 AM, Y.b. Lu <yangbo.lu@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).

Regards,
Bin

  reply	other threads:[~2017-08-23  5:28 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-22  3:46 [U-Boot] [PATCH] blk: Remove various places that do flush cache after read Bin Meng
2017-08-22  6:19 ` Stefan Roese
2017-08-22  6:31   ` Bin Meng
2017-08-22 16:49 ` York Sun
2017-08-22 22:53   ` Bin Meng
2017-08-23 15:01     ` York Sun
2017-08-23  3:14   ` Qiang Zhao
2017-08-23  3:29     ` Y.b. Lu
2017-08-23  5:28       ` Bin Meng [this message]
2017-08-24  3:54         ` Y.b. Lu
2017-08-23 16:06 ` York Sun
2017-08-24 16:45 ` Joe Hershberger
2017-08-27 20:09 ` Simon Glass

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