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>
date Thu, 27 Feb 2020 01:09:48 +0000
parents efb93f3e4ac7
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efb93f3e4ac7 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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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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11 repository), but booting from flash in mode 1 (the flash boot mode used by
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Mychaela Falconia <falcon@freecalypso.org>
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12 FC Magnetite, which is our primary firmware) was troubled. The exact failure
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Mychaela Falconia <falcon@freecalypso.org>
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13 mode and the root cause were never solved, but the issue most likely involved
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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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15 in mode 0 and not in serial downloading), and because Calypso's FDP output goes
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Mychaela Falconia <falcon@freecalypso.org>
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16 low during watchdog reset (or at least TI's CAL000 document says so), it is
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Mychaela Falconia <falcon@freecalypso.org>
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17 plausible that the root cause involved the Spansion flash chip getting unhappy
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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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22 unconnected) and feature a new flash reset circuit of our own design that meets
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Mychaela Falconia <falcon@freecalypso.org>
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23 the reset timing requirements of our Spansion flash chip, hence the flash boot
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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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25 of our current or future boards. However, our little flash-boot-wa program is
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Mychaela Falconia <falcon@freecalypso.org>
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26 kept around: removing a previously-released 120-byte program for no good reason
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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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31 C1xx phones), thereby indirectly booting the made-for-boot-mode-1 firmware image
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Mychaela Falconia <falcon@freecalypso.org>
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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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Mychaela Falconia <falcon@freecalypso.org>
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38 peculiar use case. The flash-boot-wa.srec helper can also be booted via
efb93f3e4ac7 doc/Flash-boot-wa: explanatory article added
Mychaela Falconia <falcon@freecalypso.org>
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39 fc-xram.