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To: Boris Brezillon <boris.brezillon@free-electrons.com>,
 Murali Karicheri <m-karicheri2@ti.com>
Cc: linux-mtd@lists.infradead.org
From: Petr Kulhavy <petr@barix.com>
Subject: DaVinci NAND: disable subpage write (28c015)
Message-ID: <5719DEB9.1020909@barix.com>
Date: Fri, 22 Apr 2016 10:20:09 +0200
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Hi,

this email refers to the commit: 
28c015a9daabe4ed3aeb0ccf669a3f1c2b8b81d5 on drivers/mtd/nand/davinci-nand.c.
This commit sets the NAND_NO_SUBPAGE_WRITE option for "ti,keystone-nand" 
to workaround a HW issue on the controller.

Disabling subpage write however should be made a general option because 
some NAND chips do not support subpage write at all. Subpage write is a 
feature of the NAND chip, not the NAND interface. In combination with  
"ti,davinci-nand" there is no option to disable subpage write.
In my case I'm struggling with this issue on the AM1808 with a 1Gb 
Micron NAND (MT29F1GxxABB).

My proposal would be to add a boolean property 
"ti,davinci-disable-subpage-write" or similar, which sets the 
NAND_NO_SUBPAGE_WRITE option.
I'm also wondering why no other binding is addressing this, as it is a 
general problem.

I wanted to collect your opinion before submitting a patch.

Thanks
Petr