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doc/Loadtools-performance: complete for now
author Mychaela Falconia <falcon@freecalypso.org>
date Tue, 25 Feb 2020 01:33:23 +0000
parents ab4021fb1c66
children 6824c4d55848
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1 Here are the expected run times for the flash dump2bin operation of dumping the
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2 entire flash content of a Calypso GSM device:
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3
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4 Dump of 4 MiB flash (e.g., Openmoko GTA01/02 or Mot C139/140) at 115200 baud:
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5 12m53s
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6
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7 The same 4 MiB flash dump at 812500 baud: 1m50s
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8
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9 Dump of 8 MiB flash (e.g., Mot C155/156) at 812500 baud: 3m40s
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11 Because of the architecture of fc-loadtool and its loadagent back-end, the run
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12 time of a flash dump operation depends only on the serial baud rate and the
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13 size of the flash area to be dumped; it should not depend on the USB-serial
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14 adapter type or any host system properties, as long as the host system and
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15 serial adapter combination supports the desired baud rate. In contrast, flash
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16 programming and fc-xram loading operations are quite different in that their
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17 run times do depend on the host system and USB-serial adapter or other serial
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18 port hardware - this host system dependency exists because of the way these
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19 operations are implemented in our architecture.
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20
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21 Here are some examples of expected flash programming times, all obtained on the
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22 Mother's Slackware 14.2 host system:
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24 Flashing an Openmoko GTA02 modem (K5A3281CTM flash chip) with a new firmware
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25 image (2376448 bytes), using a PL2303 USB-serial cable at 115200 baud: 7m35s
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27 Flashing the same OM GTA02 modem with the same fw image, using a CP2102
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28 USB-serial cable at 812500 baud: 1m52s
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30 Flashing a Magnetite hybrid fw image (2378084 bytes) into an FCDEV3B board
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31 (S71PL129N flash chip) via an FT2232D adapter at 812500 baud: 2m11s
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33 These times are just for the flash program-bin operation, not counting the
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34 flash erase which must be done first. Flash erase times are determined
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35 entirely by physical processes inside the flash chip and are not affected by
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36 software design or the serial link: for each sector to be erased, fc-loadtool
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37 issues the sector erase command to the flash chip and then polls the chip for
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38 operation completion status; the polling is done over the serial link and thus
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39 may seem very slow, but the extra bit of latency added by the finite polling
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40 speed is still negligible compared to the time of the actual sector erase
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41 operation inside the flash chip. In contrast, the execution time of a flash
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42 program-bin operation is a sum of 3 components:
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44 * The time it takes for the bits to be transferred over the serial link;
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45 * The time it takes for the flash programming operation to complete on the
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46 target (physics inside the flash chip);
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47 * The overhead of command-response exchanges between fc-loadtool and loadagent.
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49 XRAM loading via fc-xram is similar to flash programming in that fc-xram sends
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50 a separate ML command to loadagent for each S-record, thus the total XRAM image
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51 loading time is not only the serial bit transfer time, but also the overhead of
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52 command-response exchanges between fc-xram and loadagent. The flash programming
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53 times listed above include flashing an FC Magnetite fw image into an FCDEV3B,
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54 which took 2m11s; doing an fc-xram load of the same FC Magnetite fw image (built
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55 as ramimage.srec) into the same FCDEV3B via the same FT2232D adapter at 812500
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56 baud takes 2m54s.
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58 Why does XRAM loading take longer than flashing? Shouldn't it be faster because
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59 the flash programming step on the target is replaced with a simple memcpy()?
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60 Answer: fc-xram is currently slower than flash program-bin because the latter
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61 sends 256 bytes at a time to loadagent, whereas fc-xram sends one S-record at a
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62 time; the division of the image into S-records is determined by the tool that
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63 generates the SREC image, but TI's hex470 post-linker generates images with 30
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64 bytes of payload per S-record. Having the operation proceed in smaller chunks
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65 increases the overhead of command-response exchanges and thus increases the
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66 overall time.