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Date: Mon, 08 Jun 2009 19:30:45 +0200
From: Albrecht =?iso-8859-1?b?RHJl3w==?= <albrecht.dress@arcor.de>
Subject: Re: [PATCH V2 2/2] mtd/maps/mtd-ram: add an of-platform driver
To: Wolfram Sang <w.sang@pengutronix.de>
In-Reply-To: <20090608163540.GA16384@pengutronix.de> (from
	w.sang@pengutronix.de on Mon Jun  8 18:35:40 2009)
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	linux-mtd@lists.infradead.org, Ben Dooks <ben-linux@fluff.org>,
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Am 08.06.09 18:35 schrieb(en) Wolfram Sang:
>> Question: why is bank-width even relevant for a RAM device?
>=20
> The underlying map_ram-driver uses it once while erasing. The =20
> question remains if this is really needed?

Am 06.06.09 18:16 schrieb(en) Albrecht Dre=DF:
> At least if the RAM is attached to the 5200's Local Plus Bus in =20
> 16-bit mode, no byte write accesses are allowed (byte /reads/ work, =20
> though).  I have a tweak (which I will post next week) to address =20
> this case, which depends upon this setting.

To put this clearer: on '5200 based systems, the driver (more specific: =20
the function inline_map_copy_to()) *must* know whether the hardware is =20
connected in 8-bit or 16-bit mode to the Local Plus Bus, as byte writes =20
(issued by memcpy_toio()) will fail for the latter setup (probably the =20
same applies for byte and word writes in 32-bit mode).

IMHO, this information should be passed using the device tree.  The =20
"bank-width" seems to be an obvious choice for that.

Best, Albrecht.

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