linux-kernel - Re: [PATCH 5/9] mtd: pxa3xx_nand: add support for the Marvell Berlin nand controller

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Message-ID: <20150211163343.GH11169@kwain>
Date:	Wed, 11 Feb 2015 17:33:43 +0100
From:	Antoine Tenart <antoine.tenart@...e-electrons.com>
To:	Robert Jarzmik <robert.jarzmik@...e.fr>
Cc:	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Antoine Tenart <antoine.tenart@...e-electrons.com>,
	thomas.petazzoni@...e-electrons.com, zmxu@...vell.com,
	linux-kernel@...r.kernel.org, linux-mtd@...ts.infradead.org,
	ezequiel.garcia@...e-electrons.com, jszhang@...vell.com,
	computersforpeace@...il.com, dwmw2@...radead.org,
	linux-arm-kernel@...ts.infradead.org,
	sebastian.hesselbarth@...il.com
Subject: Re: [PATCH 5/9] mtd: pxa3xx_nand: add support for the Marvell Berlin
 nand controller

Robert,

On Tue, Feb 10, 2015 at 08:50:41PM +0100, Robert Jarzmik wrote:
> Boris Brezillon <boris.brezillon@...e-electrons.com> writes:
> > On Tue, 27 Jan 2015 15:10:12 +0100
> > Antoine Tenart <antoine.tenart@...e-electrons.com> wrote:
> >
> >> The nand controller on Marvell Berlin SoC reuse the pxa3xx nand driver
> >> as it quite close. The process of sending commands can be compared to
> >> the one of the Marvell armada 370: read and write commands are done in
> >> chunks.
> >> 
> >> But the Berlin nand controller has some other specificities which
> >> require some modifications of the pxa3xx nand driver:
> >> - there are no IRQ available so we need to poll the status register: we
> >>   have to use our own cmdfunc Berlin function, and early on the probing
> >>   function.
> >> - PAGEPROG are very different from the one used in the pxa3xx driver,
> >>   so we're using a specific process for this one
> >> - the SEQIN command is equivalent to a READ0 command
> >> - the RNDOUT command must be used to perform a read operation, and the
> >>   command is not NAND_CMD_RNDOUT
> >> - the ERASE1 command is specific (0xd060)
> >> 
> >> Signed-off-by: Antoine Tenart <antoine.tenart@...e-electrons.com>
> 
> Given all the differences, the PIO mode instead of the current interrupt model,
> and the berlin specific functions (nand_start, ...), wouldn't it be an idea to :
>  - extract the common functions to mrvl-nand-lib.c
>  - the remaining would be in pxa3xx_nand.c
>  - the new code will be in berlin_nand.c
> 
> All these ifs per variant will add complexity to the current driver, won't they
> ?

Given the current state of this driver I believe this would be a better
idea to first rework it to use the nand framework properly. Then it will
be possible to have a look on what we have, to decide whether or not a
mrvl-nand-lib is needed.

Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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