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annotate target-utils/compalstage/README @ 992:a7b0b426f9ca

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target-utils: boot ROM UART autodetection revamped The new implementation should work with both the familiar Calypso C035 boot ROM version found in our regular targets as well as the older Calypso F741979B version found on the vintage D-Sample board.
author Mychaela Falconia <falcon@ivan.Harhan.ORG>
date Wed, 30 Dec 2015 21:28:41 +0000
parents 48c08499cede
children
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48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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1 FreeCalypso loadtools have been designed from the beginning to work through
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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2 the Calypso chip's own boot ROM. This approach works great for Openmoko and
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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3 Pirelli targets, but Compal phones unfortunately have this Calypso boot ROM
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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4 disabled at the board level. To run our own code in these phones instead of
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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5 booting the regular firmware, we need to go through Compal's own boot code.
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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6 The latter allows loading code into IRAM and jumping to it, but not in the
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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7 same way as how we do it through the Calypso boot ROM.
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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8
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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9 One could argue that the "proper" way to support these Compal phones would be
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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10 to build a different version of our loadagent that is designed to be loaded
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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11 through Compal's boot code instead of the Calypso boot ROM, and then redesign
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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12 our fc-loadtool and fc-xram utilities to work with different loadagents loaded
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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13 in different ways on different target devices. But I don't feel like doing
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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14 that - too invasive to the once-clean design of loadtools.
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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15
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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16 Hence I am adopting a different solution that works in the same way as
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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17 OsmocomBB's "chain loading": the IRAM image that is fed to Compal's boot code
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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18 is not our real loadagent, but a tiny piece of code that enables the Calypso
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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19 boot ROM and jumps to it. All loadtools host programs will include this
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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20 optional "Compal stage" at the beginning, enabled for targets that need it,
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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21 but will then always fall into the Calypso boot ROM IRAM download path.
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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22
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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23 The approach I'm adopting is doubly inefficient for Mot C139/140 phones whose
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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24 bootloader effectively requires that the downloaded image be ~15 KiB long
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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25 even when we only need to download 32 bytes. But hey, our ultimate goal is to
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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26 produce our own Calypso phones, rather than hack those made by diabolical
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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27 manufacturers who do not Respect Your Freedom; running our own gsm-fw on the
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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28 Mot C139 is only a transitional step, so making fc-loadtool/fc-xram entry
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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29 slower by a second or two is probably an acceptable price for keeping the
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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30 code clean for the boot-ROM-enabled free world.
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31
48c08499cede compalstage binaries built
Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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32 In this directory we build the several different versions of compalstage
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Michael Spacefalcon <msokolov@ivan.Harhan.ORG>
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33 needed for different C1xx models.