Subject: Re: [PATCH 05/11] [POWERPC] TQM5200 DTS

From: Martin Krause <[email-masked]>
Date: Thu, 25 Oct 2007 02:57:23 -0700 (PDT)

< +		flash@00000000 {
< +			compatible = "cfi-flash";
< +			reg = <00000000 02000000>;
< +			bank-width = <4>;
< +			device-width = <2>;
< +			#size-cells = <1>;
< +			#address-cells = <1>;
< +			partition@0 {
< +				label = "firmware";
< +				reg = <0 a0000>;
< +			};
< +			partition@a0000 {
< +				label = "dtb";
< +				reg = <a0000 20000>;
< +			};
< +			partition@c0000 {
< +				label = "kernel";
< +				reg = <c0000 240000>;
< +			};
< +			partition@300000 {
< +				label = "initrd";
< +				reg = <300000 200000>;
< +			};
< +			partition@500000 {
< +				label = "small-fs";
< +				reg = <500000 400000>;
< +			};
< +			partition@900000 {
< +				label = "misc";
< +				reg = <900000 800000>;
< +			};
< +			partition@1100000 {
< +				label = "big-fs";
< +				reg = <1100000 f00000>;
< +			};
< +		};
< +	};

This MTD layout only works on boards with 32 MiB (or 64 MiB) flash
memory. On TQM5200 boards with smaller Flashes (16 MiB, 8 MiB and 4 MiB) 
the MTD partition borders do not match with the physikal memory borders.
On a board with 16 MiB FLASH for example the "big-fs" _and_ the "misc"
partition could not be used. "big-fs", because the memory is too small
(which is OK) and "misc", because it overlaps 1 MiB over the physikal
flash border. So only the first 9 MiB of the flash could be used in Linux.
The remaining 7 MiB couldn't be accessed.

I would propose a Flash layout, where the (filesystem) partitions end 
on powers of two, to match the physical flash boarders:

			partition@0 {
				label = "firmware";
				reg = <0 a0000>;
			};
			partition@a0000 {
				label = "dtb";
				reg = <a0000 20000>;
			};
			partition@c0000 {
				label = "kernel";
				reg = <c0000 180000>;
			};
			partition@240000 {
				label = "initrd";
				reg = <240000 1c0000>;
			};
			partition@400000 {
				label = "small-fs";
				reg = <400000 400000>;
			};
			partition@800000 {
				label = "misc";
				reg = <800000 800000>;
			};
			partition@1000000 {
				label = "big-fs";
				reg = <1000000 1000000>;
			};
		};
	};

Best Regards,
Martin Krause
-- 
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