Specifications

Be aware that cramfs is a read-only filesystem.
14.3.26.3. Hints and Notes
XIP conserves RAM at the expense of flash. This might be useful if you have a big flash memory and
little RAM.
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Flash memory used for XIP must be readable all the time e.g. this excludes installation and usage the
character device or MTD flash drivers, because they do device probing, sector erase etc.
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The XIP extension is currently only available for PowerQUICC™I 8xx but can easily be extended to
other architectures.
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Currently only up to 8 MB of ROM/Flash are supported.•
The original work was done for the amanda system.•
Special thanks goes to David Petersen for collecting the availible XIP extension sources and
highlighting how to put all the pieces together.
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14.3.26.4. Space requirements and RAM saving, an example
For ppc 8xx, all figures are in bytes:
Normal kernel + linear cramfs (patched):
pImage: 538062
cramfs: 1081344
total: used: free: shared: buffers: cached:
Mem: 14921728 3866624 11055104 2781184 0 2240512
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XIP kernel + linear cramfs:
pImage: 1395952
cramfs: 1081344
total: used: free: shared: buffers: cached:
Mem: 16175104 3940352 12234752 2822144 0 2240512
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XIP kernel + XIP cramfs (chmod +t: busybox, initd, libc):
pImage: 1395952
cramfs: 1871872
total: used: free: shared: buffers: cached:
Mem: 16175104 2367488 13807616 610304 0 671744
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The actual RAM saving is here approximately 1.1MB + 1.5M = 2.6 MB.
Have fun with XIP.
Wolfgang Grandegger ([e-mail])
linux-2.4.4-2002-03-21-xip.patch.gz: Linux patches for XIP on MPC8xx•
14.3.27. Use SCC UART with Hardware Handshake
Question:
14.3.27. Use SCC UART with Hardware Handshake 193