FreeCalypso > hg > fc-magnetite
comparison doc/Flash-boot-mode-hack @ 241:63c12cba5ed5
implemented optional workaround for the flash boot problem on FCDEV3B
| author | Mychaela Falconia <falcon@freecalypso.org> |
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| date | Tue, 02 May 2017 02:53:36 +0000 |
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| 240:9034c3a7267e | 241:63c12cba5ed5 |
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| 1 There are two ways in which a flashed firmware image may be booted, which we | |
| 2 call mode 0 and mode 1 - see the Flash-boot-modes write-up in the | |
| 3 freecalypso-tools repository for the details. All TI official firmwares | |
| 4 including our TCS211 reference version have used flash boot mode 1, and the | |
| 5 present Magnetite firmware is unchanged in this regard. | |
| 6 | |
| 7 Some FCDEV3B boards have a non-understood hardware problem that causes flash | |
| 8 boot to fail (the visible symptom is a dead hang with even JTAG not working) | |
| 9 when the firmware image in flash uses boot mode 1. It is not currently known | |
| 10 how many boards are affected by this problem; it is possible that the Mother's | |
| 11 S/N 001 board is the only one that exhibits this oddity. | |
| 12 | |
| 13 Once the discovery was made that the flash boot problem occurs only when the fw | |
| 14 image uses flash boot mode 1, a workaround became apparent: switch to using | |
| 15 flash boot mode 0. Redesigning Magnetite fw to use interrupt and exception | |
| 16 vectors in the ROM branching to 0x80001C-0x800034 in IRAM is not in line with | |
| 17 the Mother's vision, but a surgical hack to make the Magnetite fw flash image | |
| 18 receive control from the boot ROM in mode 0, disable the boot ROM via the | |
| 19 FFFF:FB10 register and jump to 0 as if in mode 1 is quite doable, and it | |
| 20 accomplishes the job of producing a flash image of FC Magnetite that boots | |
| 21 without a hitch on the flash-boot-challenged FCDEV3B. | |
| 22 | |
| 23 The standard FC Magnetite build is unchanged and unaffected, i.e., the hack in | |
| 24 question is NOT applied by default. However, if you have a board that has | |
| 25 trouble booting the regular Magnetite fwimage.bin that uses flash boot mode 1, | |
| 26 you can run 'make fwimage.mode0' in your build directory to get an image patched | |
| 27 with the flash boot mode 0 hack. |