FreeCalypso > hg > freecalypso-tools
annotate doc/Flash-boot-wa @ 619:f82551c77e58
libserial-newlnx: ASYNC_LOW_LATENCY patch reverted
Reports from Das Signal indicate that loadtools performance on Debian
is about the same as on Slackware, and that including or omitting the
ASYNC_LOW_LATENCY patch from Serg makes no difference. Because the
patch in question does not appear to be necessary, it is being reverted
until and unless someone other than Serg reports an actual real-world
system on which loadtools operation times are slowed compared to the
Mother's Slackware reference and on which Slackware-like performance
can be restored by setting the ASYNC_LOW_LATENCY flag.
author | Mychaela Falconia <falcon@freecalypso.org> |
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date | Thu, 27 Feb 2020 01:09:48 +0000 |
parents | efb93f3e4ac7 |
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doc/Flash-boot-wa: explanatory article added
Mychaela Falconia <falcon@freecalypso.org>
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1 There is a tiny (120 bytes SREC file) program called flash-boot-wa that was |
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2 written in the spring of 2017 for the purpose of working around a problem that |
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Mychaela Falconia <falcon@freecalypso.org>
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3 happened on only one first-batch FCDEV3B board and never happened on any other |
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4 board - but Murphy's law had it that this one troubled board just had to be the |
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Mychaela Falconia <falcon@freecalypso.org>
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5 one on which my (Mother Mychaela's) very initial development and bring-up work |
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6 was done. |
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7 |
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8 The defect exhibited on that one board was as follows: it had no problem booting |
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9 serially (fc-iram, fc-loadtool, fc-xram) and it had no problem booting from |
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Mychaela Falconia <falcon@freecalypso.org>
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10 flash in mode 0 (see the Flash-boot-modes article in the freecalypso-docs |
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11 repository), but booting from flash in mode 1 (the flash boot mode used by |
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12 FC Magnetite, which is our primary firmware) was troubled. The exact failure |
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13 mode and the root cause were never solved, but the issue most likely involved |
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14 the watchdog reset in some way (it occurs as part of flash boot mode 1 but not |
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15 in mode 0 and not in serial downloading), and because Calypso's FDP output goes |
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16 low during watchdog reset (or at least TI's CAL000 document says so), it is |
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17 plausible that the root cause involved the Spansion flash chip getting unhappy |
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18 as a result of being jerked with extra resets which don't meet its reset timing |
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19 requirements. |
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20 |
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21 Our new FCDEV3B V2 boards no longer use Calypso's FDP output (it is left |
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22 unconnected) and feature a new flash reset circuit of our own design that meets |
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23 the reset timing requirements of our Spansion flash chip, hence the flash boot |
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24 problem seen on that one FCDEV3B S/N 001 board is not expected to recur on any |
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25 of our current or future boards. However, our little flash-boot-wa program is |
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26 kept around: removing a previously-released 120-byte program for no good reason |
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27 is not the way of FOSS. |
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28 |
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29 This flash-boot-wa program is loaded serially via fc-iram; it disables the boot |
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30 ROM and jumps to address 0 (the opposite of what we do in compalstage for Mot |
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31 C1xx phones), thereby indirectly booting the made-for-boot-mode-1 firmware image |
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32 in the flash. The intended usage was as follows: |
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33 |
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34 fc-iram -h fcfam /dev/ttyXXX /opt/freecalypso/target-bin/flash-boot-wa.srec rvinterf |
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35 |
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36 It is also worth noting that fc-iram has been extended to support second program |
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Mychaela Falconia <falcon@freecalypso.org>
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37 invokation just like fc-xram (used in the invokation line above) just for this |
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38 peculiar use case. The flash-boot-wa.srec helper can also be booted via |
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39 fc-xram. |