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Date: Wed, 9 Jan 2019 22:52:08 +0100
From: Boris Brezillon <bbrezillon@kernel.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Boris Brezillon <boris.brezillon@bootlin.com>, Maxim Levitsky
 <maximlevitsky@gmail.com>, Tudor Ambarus <tudor.ambarus@microchip.com>,
 Masahiro Yamada <yamada.masahiro@socionext.com>, Richard Weinberger
 <richard@nod.at>, Marc Gonzalez <marc.w.gonzalez@free.fr>, Janusz
 Krzysztofik <jmkrzyszt@gmail.com>, Stefan Agner <stefan@agner.ch>, Marek
 Vasut <marek.vasut@gmail.com>, Harvey Hunt <harveyhuntnexus@gmail.com>,
 linux-mtd@lists.infradead.org, Miquel Raynal <miquel.raynal@bootlin.com>,
 Han Xu <han.xu@nxp.com>, Xiaolei Li <xiaolei.li@mediatek.com>, Brian Norris
 <computersforpeace@gmail.com>, David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH v3 15/22] mtd: rawnand: fsmc: Stop implementing
 ->select_chip()
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On Wed, 9 Jan 2019 22:30:18 +0100
Linus Walleij <linus.walleij@linaro.org> wrote:

> On Wed, Jan 9, 2019 at 9:54 PM Boris Brezillon <bbrezillon@kernel.org> wrote:
> > [Me]  
> > > I guess that is normal for FSMC: only one CS. It seems a bit
> > > aggressive to toggle CS on/off between every command like this,
> > > I suspect the FSMC isn't really built for that but shakes apart
> > > or something.  
> >
> > Hm, that would be weird. There's indeed timing constraints on the NAND
> > chip side, but none infringing those constraints should not trigger an
> > external abort exception.  
> 
> The manual contains this (the same bit, just another name than
> in the driver):
> 
> PBKEN PC-card/NAND-Flash chip-select enable.
> Enables the corresponding chip-select.
> If a disabled chip-select is accessed, an HRESP = ERROR is generated
> on the AHB bus.
> 0: disabled (default after reset)
> 1: enabled

It's still not clear what this bit does. Do you have access to the CS
pin on the board?

> 
> > Can you check which phys range is remapped at
> > 0xcc960000?  
> 
> No idea how to do that but I'll see if I can figure it out...

print the __iomem values returned by devm_ioremap_resource() and find
the one that matches this address.