linux-kernel - Re: [PATCH v4] mtd: nand: omap: Synchronize the access to the ECC engine

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Message-ID: <20141105210206.GS23619@ld-irv-0074>
Date:	Wed, 5 Nov 2014 13:02:06 -0800
From:	Brian Norris <computersforpeace@...il.com>
To:	Rostislav Lisovy <lisovy@...il.com>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Roger Quadros <rogerq@...com>, sojkam1@....cvut.cz,
	michal.vokac@...ap.cz, Rostislav Lisovy <lisovy@...ica.cz>
Subject: Re: [PATCH v4] mtd: nand: omap: Synchronize the access to the ECC
 engine

On Wed, Oct 29, 2014 at 11:10:59AM +0100, Rostislav Lisovy wrote:
> The AM335x Technical Reference Manual (spruh73j.pdf) says
> "Because the ECC engine includes only one accumulation context,
> it can be allocated to only one chip-select at a time ... "
> (7.1.3.3.12.3). Since the commit 97a288ba2cfa ("ARM: omap2+:
> gpmc-nand: Use dynamic platform_device_alloc()") gpmc-nand
> driver supports multiple NAND flash devices connected to
> the single controller.
> Use global 'struct nand_hw_control' among multiple NAND
> instances to synchronize the access to the single ECC Engine.
> 
> Tested with custom AM335x board using 2x NAND flash chips.
> 
> Signed-off-by: Rostislav Lisovy <lisovy@...ica.cz>
> Acked-by: Roger Quadros <rogerq@...com>
> ---
> Changes since v3:
> * Make the omap_gpmc_controller static (Frans Klaver)
> 
> Changes since v2:
> * Do not use custom locks. Use global 'struct nand_hw_control'
>   among multiple NAND instances and it will do the work for us
>   (Roger Quadros)
> 
> Changes since v1:
> * Since not all the read/write operations are performed by the
>   omap_read(write)_page_bch() functions use the locks directly on
>   those places that configure the ECC engine (take the lock) and
>   read the result from the ECC engine (release the lock).
>   This approach should cover read/write operations with all
>   possible ECC modes. (Roger Quadros)

Pushed to l2-mtd.git. Thanks!

Brian
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