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annotate target-utils/libbase/waitarm.S @ 609:ffd606adb039

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CHANGES: libserial ASYNC_LOW_LATENCY change documented
author Mychaela Falconia <falcon@freecalypso.org>
date Sat, 22 Feb 2020 19:07:46 +0000
parents 06ad5e30e8d0
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
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1 /*
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2 * This assembly module provides a wait_ARM_cycles() function similar to
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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3 * the one in TI's firmware; it is meant to gradually replace and phase out
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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4 * osmo_delay_ms(). One loop count for this function equals 4 ARM clock
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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5 * cycles when running out of IRAM; if the ARM clock is 52 MHz, 13 loop counts
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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6 * equal one microsecond.
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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7 *
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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8 * Note the instruction sequence difference from TI's firmware version:
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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9 * we use the SUBS instruction (equivalent of plain SUB in Thumb) and omit
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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10 * the CMP, which is why our version is 4 cycles per loop (when running
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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11 * out of IRAM), as opposed to 5 cycles per loop (plus wait states as they
06ad5e30e8d0 target-utils: wait_ARM_cycles() changed to 4 cycles per loop
Mychaela Falconia <falcon@freecalypso.org>
parents: 453
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12 * execute from flash) in TI's fw version.
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13 */
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6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
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15 .text
6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
Mychaela Falconia <falcon@freecalypso.org>
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16 .code 32
6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
Mychaela Falconia <falcon@freecalypso.org>
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17 .globl wait_ARM_cycles
6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
Mychaela Falconia <falcon@freecalypso.org>
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18 wait_ARM_cycles:
6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
Mychaela Falconia <falcon@freecalypso.org>
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19 cmp r0, #0
6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
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20 bxeq lr
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21 1: subs r0, r0, #1
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6228d27738d1 target-utils: wait_ARM_cycles() added to libbase
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22 bne 1b
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23 bx lr