contrib/loaders/flash/nrf5/nrf5.S

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2014 Angus Gratton                                      *
   5  *   gus@projectgus.com                                                    *
   6  ***************************************************************************/
   7
   8         .text
   9         .syntax unified
  10         .cpu cortex-m0
  11         .thumb
  12
  13 /*
  14  * Params :
  15  * r0 = byte count
  16  * r1 = buffer start
  17  * r2 = buffer end
  18  * r3 = target address
  19  * r6 = watchdog refresh value
  20  * r7 = watchdog refresh register address
  21  */
  22
  23         .thumb_func
  24         .global _start
  25 _start:
  26 wait_fifo:
  27         // Kick the watchdog
  28         str     r6, [r7, #0]
  29         // Load write pointer
  30         ldr     r5, [r1, #0]
  31         // Abort if it is NULL
  32         cmp     r5, #0
  33         beq.n   exit
  34         // Load read pointer
  35         ldr     r4, [r1, #4]
  36         // Continue waiting if it equals the write pointer
  37         cmp     r4, r5
  38         beq.n   wait_fifo
  39         // Copy one word from buffer to target, and increment pointers
  40         ldmia   r4!, {r5}
  41         stmia   r3!, {r5}
  42         // If at end of buffer, wrap back to buffer start
  43         cmp     r4, r2
  44         bcc.n   no_wrap
  45         mov     r4, r1
  46         adds    r4, #8
  47 no_wrap:
  48         // Update read pointer inside the buffer
  49         str     r4, [r1, #4]
  50         // Deduce the word transferred from the byte count
  51         subs    r0, #4
  52         // Start again
  53         bne.n   wait_fifo
  54 exit:
  55         // Wait for OpenOCD
  56         bkpt    #0x00
  57
  58         .pool