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doc/Compal-unlock: added cautionary note about flashing firmwares containing boot code that checks the word at 0x2060
author Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
date Sat, 21 Jun 2014 06:55:27 +0000
parents f81a931f9172
children 7e305184b0b4
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425:f81a931f9172 426:1060bf70d95d
32 we have on Openmoko and Pirelli phones, but unfortunately the hardware we have 32 we have on Openmoko and Pirelli phones, but unfortunately the hardware we have
33 available is not wired that way. 33 available is not wired that way.
34 34
35 However, Mot/Compal's standard firmware on these phones includes a bootloader, 35 However, Mot/Compal's standard firmware on these phones includes a bootloader,
36 a part that executes before any of the rest of the fw image is allowed to 36 a part that executes before any of the rest of the fw image is allowed to
37 execute or made use of in any way, and this Compal-specific bootloader has a 37 execute or is made use of in any way, and this Compal-specific bootloader has a
38 provision for interrupting the boot process and diverting it to an externally- 38 provision for interrupting the boot process and diverting it to an externally-
39 supplied piece of code loaded over the serial line. Older fw versions have 39 supplied piece of code loaded over the serial line. Older fw versions have
40 this feature enabled unconditionally, but some of the newer versions have a 40 this feature enabled unconditionally, but some of the newer versions have a
41 malfeature whereby the serial boot interrupt and code download possibility may 41 malfeature whereby the serial boot interrupt and code download possibility may
42 be disabled. Some C1xx phones out in the wild, particularly all North American 42 be disabled. Some C1xx phones out in the wild, particularly all North American
263 The same procedure should be followed for flashing all firmwares for C11x/123 263 The same procedure should be followed for flashing all firmwares for C11x/123
264 and C139/140 phones. In the case of C11x/123, adjust the length for the "main" 264 and C139/140 phones. In the case of C11x/123, adjust the length for the "main"
265 erase and program operations appropriately for the flash configuration in your 265 erase and program operations appropriately for the flash configuration in your
266 phone. 266 phone.
267 267
268 One last word of caution: if you are going to flash some fw version other than
269 the unlocked North American C139 one discussed above, please check to see what
270 boot code version it includes, and whether or not that version has the
271 malfeature of checking the flash word at 0x2060 for the serial access control
272 flag. If the fw version you are seeking to play with has boot code with that
273 malfeature present, the bricking vulnerability window extends until you not
274 only program the new boot code into flash, but also program 0xDDDDDDDD into
275 that 0x2060 word. You've been warned.
276
268 C155/156 differences 277 C155/156 differences
269 ==================== 278 ====================
270 279
271 C155/156 phones are nicer than the others in that they use a flash chip with a 280 C155/156 phones are nicer than the others in that they use a flash chip with a
272 "bottom boot" configuration. C11x/123 and C139/140 use "top boot" flash chips, 281 "bottom boot" configuration. C11x/123 and C139/140 use "top boot" flash chips,