linux-kernel - Re: [PATCH v2] mtd: nand: denali: allow to override max

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Message-ID: <CAK7LNASWa-8Ag5azvQS+TT3nkXoeHFxmvJF0XDm4nTULb1vE+A@mail.gmail.com>
Date:	Sat, 2 Apr 2016 14:16:10 +0900
From:	Masahiro Yamada <yamada.masahiro@...ionext.com>
To:	linux-mtd@...ts.infradead.org
Cc:	Graham Moore <grmoore@...nsource.altera.com>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>,
	Masahiro Yamada <yamada.masahiro@...ionext.com>,
	devicetree@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Richard Weinberger <richard@....at>,
	Kumar Gala <galak@...eaurora.org>,
	Boris Brezillon <boris.brezillon@...e-electrons.com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Brian Norris <computersforpeace@...il.com>,
	Rob Herring <robh+dt@...nel.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v2] mtd: nand: denali: allow to override max_banks from DT property

2016-03-29 11:33 GMT+09:00 Masahiro Yamada <yamada.masahiro@...ionext.com>:
> Commit 271707b1d817 ("mtd: nand: denali: max_banks calculation
> changed in revision 5.1") supported the new encoding of the "n_banks"
> bits of the "features" register, but there is an unfortunate case
> not covered by that commit.
>
> Panasonic (its System LSI Business Division is now Socionext) bought
> a couple of versions of this IP.  The IP released for Panasonic
> around Feb. 2012 is revision 5 and uses the old encoding for n_banks
> (2 << n_banks).  While the one released around Nov. 2012 is also
> revision 5, but it uses the new encoding (1 << n_banks).
>
> The revision register cannot distinguish these two incompatible
> hardware.  I guess this IP series is not well-organized.  I could not
> find any solution but giving max_banks from DT property.
>
> This commit works around the problem by allowing DT to set the
> max_banks forcibly.  Of course, this DT property can be optional if
> the auto detection based on the hardware registers works well.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> Acked-by: Rob Herring <robh@...nel.org>


Looks like we should take our time for discussion
to find out which is better, a new compatible string or a new DT property.

The discussion is happening in v1 thread.
http://patchwork.ozlabs.org/patch/601562/

Please hold back applying this patch.



-- 
Best Regards
Masahiro Yamada