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annotate gsm-fw/libiram/bzero.S @ 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 cbc49d533b7d
children
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cbc49d533b7d gsm-fw: new implementation of bzero() and some specialized bcopy variants
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1 /*
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2 * This ARM implementation of bzero() has been derived from:
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3 *
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4 * linux/arch/arm/lib/memzero.S
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5 *
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6 * Copyright (C) 1995-2000 Russell King
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7 *
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8 * This program is free software; you can redistribute it and/or modify
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9 * it under the terms of the GNU General Public License version 2 as
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10 * published by the Free Software Foundation.
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11 */
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12
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13 .text
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14 .code 32
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15 .globl bzero
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16
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17 /*
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18 * Align the pointer in r0. r3 contains the number of bytes that we are
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19 * mis-aligned by, and r1 is the number of bytes. If r1 < 4, then we
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20 * don't bother; we use byte stores instead.
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21 */
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22 1: subs r1, r1, #4 @ 1 do we have enough
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23 blt 5f @ 1 bytes to align with?
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24 cmp r3, #2 @ 1
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25 strltb r2, [r0], #1 @ 1
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26 strleb r2, [r0], #1 @ 1
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27 strb r2, [r0], #1 @ 1
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28 add r1, r1, r3 @ 1 (r1 = r1 - (4 - r3))
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29 /*
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30 * The pointer is now aligned and the length is adjusted. Try doing the
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31 * bzero again.
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32 */
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33
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34 bzero:
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35 mov r2, #0 @ 1
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36 ands r3, r0, #3 @ 1 unaligned?
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37 bne 1b @ 1
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38 /*
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39 * r3 = 0, and we know that the pointer in r0 is aligned to a word boundary.
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40 */
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41 3: subs r1, r1, #4
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42 strge r2, [r0], #4
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43 bgt 3b @ 1
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44 bxeq lr @ 1/2 quick exit
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45 /*
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46 * No need to correct the count; we're only testing bits from now on
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47 *
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48 * When we get here, we've got less than 4 bytes to zero. We
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49 * may have an unaligned pointer as well.
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50 */
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51 5: tst r1, #2 @ 1 2 bytes or more?
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52 strneb r2, [r0], #1 @ 1
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53 strneb r2, [r0], #1 @ 1
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54 tst r1, #1 @ 1 a byte left over
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55 strneb r2, [r0], #1 @ 1
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56 bx lr @ 1