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annotate target-utils/libbase/osmodelay.S @ 407:19e5a3e2f9c0

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fcup-settime: moved time() retrieval a little closer to the output A fundamental problem with all simple time transfer tools is that there is always some delay between the time retrieval on the source system and that transmitted time being set on the destination, and the resulting time on the destination system is off by that delay amount. This delay cannot be fully eliminated when working in a simple environment like ours, but we should make our best effort to minimize it. In the present case, moving the atinterf_init() call before the time() retrieval should make a teensy-tiny improvement.
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 11 Aug 2018 21:52:17 +0000
parents e7502631a0f9
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1 /*
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2 * This assembly module provides a replica of OsmocomBB's bogo-millisecond
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3 * delay_ms() function. It is literally a copy of what OsmocomBB's delay_ms()
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4 * compiles to with their gcc version and their optimization settings, as seen
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5 * by doing arm-elf-objdump on their lib/delay.o.
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6 *
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7 * This hack is intended for those cases where we have to copy OsmocomBB's
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8 * black magic voodoo operations with no ability to understand what is actually
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9 * needed, such as SPCA552E initialization on the Pirelli DP-L10.
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10 */
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12 .text
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13 .code 32
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14 .globl osmo_delay_ms
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15 osmo_delay_ms:
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16 mov r3, #0
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17 sub sp, sp, #4
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18 str r3, [sp]
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19 ldr r3, =1300
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20 mul r3, r0, r3
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21 b 2f
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22 1: ldr r2, [sp]
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23 ldr r2, [sp]
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24 add r2, r2, #1
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25 str r2, [sp]
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26 2: ldr r2, [sp]
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27 cmp r2, r3
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28 bcc 1b
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29 add sp, sp, #4
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30 bx lr