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From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Paul Cercueil <paul@crapouillou.net>
Cc: Mark Rutland <mark.rutland@arm.com>,
	David Woodhouse <dwmw2@infradead.org>,
	linux-mtd@lists.infradead.org, Rob Herring <robh+dt@kernel.org>,
	linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
	Brian Norris <computersforpeace@gmail.com>,
	Richard Weinberger <richard@nod.at>,
	Boris Brezillon <boris.brezillon@bolin.com>,
	Marek Vasut <marek.vasut@gmail.com>
Subject: Re: [PATCH] mtd: nand: Add support for reading ooblayout from device tree
Date: Sat, 12 May 2018 17:00:34 +0200	[thread overview]
Message-ID: <20180512170034.12779313@bbrezillon> (raw)
In-Reply-To: <1526135906.4971.0@smtp.crapouillou.net>

On Sat, 12 May 2018 11:38:26 -0300
Paul Cercueil <paul@crapouillou.net> wrote:

> Le sam. 12 mai 2018 à 10:42, Boris Brezillon 
> <boris.brezillon@bootlin.com> a écrit :
> > On Sat, 12 May 2018 08:55:40 -0300
> > Paul Cercueil <paul@crapouillou.net> wrote:
> >   
> >>  Hi Boris,
> >> 
> >>  Le 12 mai 2018 02:55, Boris Brezillon <boris.brezillon@bootlin.com> 
> >> a écrit :  
> >>  >
> >>  > Hi Paul,
> >>  >
> >>  > On Fri, 11 May 2018 23:29:12 +0200
> >>  > Paul Cercueil <paul@crapouillou.net> wrote:
> >>  >  
> >>  > > By specifying the properties "mtd-oob-ecc" and "mtd-oob-free",   
> >> it is  
> >>  > > now possible to specify from devicetree where the ECC data is   
> >> located  
> >>  > > inside the OOB region.  
> >>  >
> >>  > Why would we want to do that? I mean, ECC/free regions are ECC
> >>  > controller dependent (and NAND chip dependent for the OOB size   
> >> part),  
> >>  > so there's no reason to describe it in the DT. And more   
> >> importantly,  
> >>  > people are likely to get it wrong.
> >>  >
> >>  > I'm curious, why do you need that?  
> >> 
> >>  Good question.
> >> 
> >>  The reason is that some SoCs have no ECC controller.
> >>  The various boards for these SoCs then all use a different layout.  
> > 
> > Okay. Still think defining the layouts in the DT is a bad idea. We
> > can add a jz4740 specific property to define the layout id
> > (ingenic,nand-oob-layout = <layout-id>), but not a generic way to
> > define custom layouts for all kind of NAND controller.  
> 
> Okay.
> 
> >> 
> >>  My motivation is to get rid of this (move it to devicetree):
> >>  
> >> https://elixir.bootlin.com/linux/latest/source/arch/mips/jz4740/board-qi_lb60.c#L93
> >>  And enable the support of other boards with custom OOB layouts.  
> > 
> > Can you list the different layouts you have? I'm pretty sure there's a
> > pattern. Maybe we can even deduce the layout from the page size or OOB
> > size.  
> 
> This is the other layout I have for another ingenic device:
> http://projects.qi-hardware.com/index.php/p/qi-kernel/source/tree/od-2011-09-18/arch/mips/jz4740/board-a320.c#L125
> 
> Page size and OOB size are the same between these two devices.

Indeed. Do you know if there are other kind of layouts in the wild?
Note that <layout-id> can be a string, so if each each board is
defining its own layout, you could specify the board name here.
Otherwise, if you just have those 2 patterns, you can just name them
"contiguous" and "interleaved".

  reply	other threads:[~2018-05-12 15:00 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20180512115551.56C6E20787@mail.bootlin.com>
2018-05-12 13:42 ` Boris Brezillon
2018-05-12 14:38   ` Paul Cercueil
2018-05-12 15:00     ` Boris Brezillon [this message]
2018-05-12 17:42       ` Paul Cercueil
2018-05-12 18:02         ` Boris Brezillon
2018-05-12 18:30           ` Paul Cercueil
2018-05-11 21:29 Paul Cercueil
2018-05-12  5:55 ` Boris Brezillon

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