contrib/loaders/flash/cortex-m0.S

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2
   3 /***************************************************************************
   4  *   Copyright (C) 2014 by Angus Gratton                                   *
   5  *   Derived from stm32f1x.S:
   6  *   Copyright (C) 2011 by Andreas Fritiofson                              *
   7  *   andreas.fritiofson@gmail.com                                          *
   8  *   Copyright (C) 2013 by Roman Dmitrienko                                *
   9  *   me@iamroman.org                                                       *
  10  ***************************************************************************/
  11         .text
  12         .syntax unified
  13         .cpu cortex-m0
  14         .thumb
  15         .thumb_func
  16
  17 /* Written for NRF51822 (src/flash/nor/nrf51.c) however the NRF NVMC is
  18  * very generic (CPU blocks during flash writes), so this is actually
  19  * just a generic word-oriented copy routine for Cortex-M0 (also
  20  * suitable for Cortex-M0+/M3/M4.)
  21  *
  22  * To assemble:
  23  * arm-none-eabi-gcc -c cortex-m0.S
  24  *
  25  * To disassemble:
  26  * arm-none-eabi-objdump -o cortex-m0.o
  27  *
  28  * Thanks to Jens Bauer for providing advice on some of the tweaks.
  29  */
  30
  31         /* Params:
  32          * r0 - byte count (in)
  33          * r1 - workarea start
  34          * r2 - workarea end
  35          * r3 - target address
  36          * Clobbered:
  37          * r4 - rp
  38          * r5 - wp, tmp
  39          */
  40
  41 wait_fifo:
  42         ldr     r5, [r1, #0]    /* read wp */
  43         cmp     r5, #0          /* abort if wp == 0 */
  44         beq     exit
  45         ldr     r4, [r1, #4]    /* read rp */
  46         cmp     r4, r5          /* wait until rp != wp */
  47         beq     wait_fifo
  48
  49         ldmia   r4!, {r5}       /* "*target_address++ = *rp++" */
  50         stmia   r3!, {r5}
  51
  52         cmp     r4, r2          /* wrap rp at end of work area buffer */
  53         bcc     no_wrap
  54         mov     r4, r1
  55         adds    r4, #8          /* skip rp,wp at start of work area */
  56 no_wrap:
  57         str     r4, [r1, #4]    /* write back rp */
  58         subs    r0, #4          /* decrement byte count */
  59         bne     wait_fifo       /* loop if not done */
  60 exit:
  61         bkpt    #0