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Date:   Mon, 20 May 2019 16:31:31 +0200
From:   Miquel Raynal <miquel.raynal@bootlin.com>
To:     Stefan Agner <stefan@agner.ch>
Cc:     bbrezillon@kernel.org, richard@nod.at, dwmw2@infradead.org,
        computersforpeace@gmail.com, marek.vasut@gmail.com,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Boris Brezillon <boris.brezillon@collabora.com>
Subject: Re: [PATCH] mtd: rawnand: use longest matching pattern
Message-ID: <20190520163131.7c143ebe@xps13>
In-Reply-To: <20190419074717.22576-1-stefan@agner.ch>
References: <20190419074717.22576-1-stefan@agner.ch>
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Hi Stefan,

Stefan Agner <stefan@agner.ch> wrote on Fri, 19 Apr 2019 09:47:17 +0200:

> Sometimes the exec_op parser does not choose the optimal pattern if
> multiple patterns with optional elements are available. Since the stack
> automatically splits operations in multiple exec_op calls, a non-optimal
> pattern gets broken up into multiple calls. E.g. an OOB read using the
> vf610 driver:
>   nand: executing subop:
>   nand:     ->CMD      [0x00]
>   nand:     ->ADDR     [5 cyc: 00 08 ea 94 02]
>   nand:     ->CMD      [0x30]
>   nand:     ->WAITRDY  [max 200000 ms]
>   nand:       DATA_IN  [64 B]
>   nand: executing subop:
>   nand:       CMD      [0x00]
>   nand:       ADDR     [5 cyc: 00 08 ea 94 02]
>   nand:       CMD      [0x30]
>   nand:       WAITRDY  [max 200000 ms]
>   nand:     ->DATA_IN  [64 B]
> 
> However, the vf610 driver has a pattern which can execute the complete
> command in a single go...
> 
> This patch makes sure that the longest matching pattern is chosen
> instead of the first (potentially only partial) match. With this
> change the vf610 reads the OOB in a single exec_op call:
>   nand: executing subop:
>   nand:     ->CMD      [0x00]
>   nand:     ->ADDR     [5 cyc: 00 08 c0 1d 00]
>   nand:     ->CMD      [0x30]
>   nand:     ->WAITRDY  [max 200000 ms]
>   nand:     ->DATA_IN  [64 B]
> 
> Reported-by: Sascha Hauer <s.hauer@pengutronix.de>
> Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
> Tested-by: Stefan Agner <stefan@agner.ch>
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> ---

Applied, thanks.

Miquèl