From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailrelay005.isp.belgacom.be ([195.238.6.171]) by bombadil.infradead.org with esmtp (Exim 4.68 #1 (Red Hat Linux)) id 1JeoXv-0005yt-Cu for linux-mtd@lists.infradead.org; Thu, 27 Mar 2008 09:37:20 +0000 From: Laurent Pinchart To: linux-mtd@lists.infradead.org Subject: Re: [PATCH 2/2] [POWERPC] Describe memory-mapped RAM&ROM chips of bindings Date: Thu, 27 Mar 2008 10:37:17 +0100 References: <200803261344.26555.laurentp@cse-semaphore.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Message-Id: <200803271037.17654.laurentp@cse-semaphore.com> Cc: ben@simtec.co.uk, linuxppc-dev@ozlabs.org, Segher Boessenkool , David Gibson List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wednesday 26 March 2008 15:52, Segher Boessenkool wrote: > > + Dedicated RAM and ROM chips are often used as storage for=20 > > temporary or > > + permanent data in embedded devices. Possible usage include=20 > > non-volatile > > + storage in battery-backed SRAM, semi-permanent storage in=20 > > dedicated SRAM > > + to preserve data accross reboots and firmware storage in=20 > > dedicated ROM. > > + > > + - compatible : should contain the specific model of RAM/ROM=20 > > chip(s) > > + used, if known, followed by either "physmap-ram" or=20 > > "physmap-rom" > > + - reg : Address range of the RAM/ROM chip > > + - bank-width : Width (in bytes) of the RAM/ROM bank. Equal to the > > + device width times the number of interleaved chips. > > + - device-width : (optional) Width of a single RAM/ROM chip. If > > + omitted, assumed to be equal to 'bank-width'. >=20 > Maybe I'm rehashing some old discussion here, if so, sorry; but why > do you have bank-width and device-width here? What useful information > does it provide? If this is about saying what the preferred (or only > possible) access width is, better names are in order. device-width isn't used so we can get rid of it. bank-width is used by the= =20 map_ram driver for erase operations (mapram_erase in=20 drivers/mtd/chips/map_ram.c). To be honest I'm not sure why it uses such an= =20 inefficient approach instead of memsetting the whole area. =2D-=20 Laurent Pinchart CSE Semaphore Belgium Chauss=E9e de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 =46 +32 (2) 387 42 75