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

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 da6df2c626cf
children
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1 #include "ns16550.h"
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3 @ this module implements the elementary serial I/O operations
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5 .comm uart_base,4,4
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7 .text
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8 .code 32
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9 .global serial_out
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10 serial_out:
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11 ldr r1, =uart_base
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12 ldr r2, [r1]
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13 1: ldrb r3, [r2, #0x11] @ Calypso UART non-std register SSR
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14 tst r3, #0x01 @ Tx FIFO full flag
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15 bne 1b
0
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16 strb r0, [r2, #NS16550_THR]
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17 bx lr
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19 .global serial_in_poll
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20 serial_in_poll:
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21 ldr r1, =uart_base
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22 ldr r2, [r1]
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23 ldrb r3, [r2, #NS16550_LSR]
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24 tst r3, #NS16550_LSR_DR
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25 ldrneb r0, [r2, #NS16550_RBR]
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26 mvneq r0, #0
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27 bx lr
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29 .global serial_flush
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30 serial_flush:
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31 ldr r1, =uart_base
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32 ldr r2, [r1]
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33 1: ldrb r3, [r2, #NS16550_LSR]
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34 tst r3, #NS16550_LSR_TEMP
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35 beq 1b
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36 bx lr