FreeCalypso > hg > freecalypso-tools
annotate doc/Flash-boot-defect @ 243:b775a457940b
CHANGES: first changes since fc-host-tools-r6
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Sat, 26 Aug 2017 01:23:34 +0000 |
parents | de8f75783b3b |
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Flash-boot-defect and Flash-boot-modes documentation
Mychaela Falconia <falcon@freecalypso.org>
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1 As of this writing (2017-05-01), there is an unexplained hardware problem on |
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Flash-boot-defect and Flash-boot-modes documentation
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2 some of our FCDEV3B boards in that flashed firmware images which use flash boot |
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Flash-boot-defect and Flash-boot-modes documentation
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3 mode 1 (see the Flash-boot-modes article) fail to boot. It is not currently |
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4 known how many boards are affected by this problem; it is possible that the |
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Flash-boot-defect and Flash-boot-modes documentation
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5 Mother's S/N 001 board is the only one that exhibits this oddity. |
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6 |
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7 This problem particularly affects our FC Magnetite firmware, as the latter uses |
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8 flash boot mode 1 just like TI's TCS211 fw from which it originates. OTOH, our |
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9 FC Citrine firmware, which uses flash boot mode 0, boots just fine. A minimal |
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10 test case has been created under target-utils/flash-boot-test in this |
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11 repository: it is a simple loadagent-like standalone application that is built |
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12 to be booted from flash instead of expecting to be loaded serially, and it is |
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13 built in two versions, one for mode 0 and another for mode 1. Both versions |
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14 work on an Openmoko-made GTA02 (the mode 1 version continuously reboots every |
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15 few seconds because it doesn't disable the watchdog timer, but it is still very |
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16 clearly alive) as well as on those FCDEV3B boards which aren't affected, but on |
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17 FCDEV3B S/N 001 the mode 1 version fails to boot just like the full Magnetite |
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18 firmware. |
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19 |
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20 The Mother of FreeCalypso does not currently have any prognosis as to when or |
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21 even if the mysterious hardware problem that causes flash boot mode 1 to fail |
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22 can be fixed. Logical reasoning tells us that it must be a hardware problem, |
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23 as the flash boot mode in question works without a hitch on every pre-existing |
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24 Calypso device known to us, and similar logical reasoning tells us that the |
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25 watchdog timer probably has to be involved in some way, as it is the mechanism |
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26 underlying flash boot mode 1 (again, see the Flash-boot-modes article), but I |
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27 am at a total loss when it comes to what kind of board-level problem could |
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28 possibly produce such behaviour. But then if only the S/N 001 board is affected |
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29 and no others, it could just be a defective chip. More data points need to be |
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30 gathered before we shall know whether or not we have a real problem. |
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31 |
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32 For those who do have a flash-boot-challenged FCDEV3B board, two workarounds |
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33 have been developed, in this chronological order: |
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34 |
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35 1. One can boot the board in the serial download mode, and download a |
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36 teensy-tiny piece of code that disables the boot ROM and jumps to address 0. |
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37 If the flash contains a firmware image meant to be booted in mode 1, this |
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Mychaela Falconia <falcon@freecalypso.org>
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38 image will get indirectly booted in this manner. Run a command like this: |
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39 |
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40 fc-iram -h fcfam /dev/ttyXXX /opt/freecalypso/target-bin/flash-boot-wa.srec rvinterf |
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41 |
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42 (fc-iram has been extended to support second program invokation just like |
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43 fc-xram, just for this peculiar use case. The flash-boot-wa.srec helper can |
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44 also be booted via fc-xram.) |
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45 |
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46 2. After doing the above, I found a way to patch the Magnetite firmware image |
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Mychaela Falconia <falcon@freecalypso.org>
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47 to boot in mode 0 - see the Flash-boot-mode-hack write-up in the Magnetite |
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Mychaela Falconia <falcon@freecalypso.org>
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48 source tree. With this patch applied, FC Magnetite happily boots directly |
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49 from flash on my board without needing fc-iram or fc-xram assistance. |