contrib/loaders/watchdog/armv7m_kinetis_wdog32.s

   1 /***************************************************************************
   2  *   Copyright (C) 2017 Tomas Vanek                                        *
   3  *   vanekt@fbl.cz                                                         *
   4  *                                                                         *
   5  *   This program is free software; you can redistribute it and/or modify  *
   6  *   it under the terms of the GNU General Public License as published by  *
   7  *   the Free Software Foundation; either version 2 of the License, or     *
   8  *   (at your option) any later version.                                   *
   9  *                                                                         *
  10  *   This program is distributed in the hope that it will be useful,       *
  11  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  12  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  13  *   GNU General Public License for more details.                          *
  14  *                                                                         *
  15  *   You should have received a copy of the GNU General Public License     *
  16  *   along with this program; if not, write to the                         *
  17  *   Free Software Foundation, Inc.                                        *
  18  ***************************************************************************/
  19
  20 /*
  21         Disable watchdog, 32-bit version for newer Kinetis
  22         Parameters:
  23                 r0 ... WDOG32 base (in)
  24
  25         Used instruction set should work on both Cortex-M4 and M0+
  26 */
  27
  28         .text
  29         .syntax unified
  30         .cpu cortex-m0
  31         .thumb
  32
  33 /* WDOG registers offsets */
  34 WDOG_CS         = 0
  35 WDOG_CNT        = 4
  36 WDOG_TOVAL      = 8
  37
  38 WDOG_KEY        = 0xd928c520
  39
  40         .thumb_func
  41 start:
  42 /* test WDOG_CS bit CMD32EN */
  43         ldr     r2, [r0, WDOG_CS]
  44         ldr     r3, =0x2000
  45         tst     r2, r3
  46         ldr     r3, =WDOG_KEY
  47         beq     cmd16
  48
  49 /* WDOG_CNT = key */
  50         str     r3, [r0, WDOG_CNT]
  51         b       unlocked
  52
  53 cmd16:
  54 /* WDOG_CNT = key, halfword by halfword */
  55         strh    r3, [r0, WDOG_CNT]
  56         lsrs    r3, r3, #16
  57         strh    r3, [r0, WDOG_CNT]
  58
  59 /* WDOG_CS: clear EN bit 7, set UPDATE bit 5 */
  60 unlocked:
  61         movs    r4, #0x80
  62         bics    r2, r4
  63         movs    r4, #0x20
  64         orrs    r2, r4
  65         str     r2, [r0, WDOG_CS]
  66 /* All active WDOG registers have to be updated, set dummy timeout */
  67 /* WDOG_TOVAL = 0x400 */
  68         ldr     r3, =0x400
  69         str     r3, [r0, WDOG_TOVAL]
  70 /* OpenOCD checks exit point address. Jump to the very end. */
  71         b       done
  72
  73         .pool
  74
  75 /* Avoid padding at .text segment end. Otherwise exit point check fails. */
  76         .skip   ( . - start + 2) & 2, 0
  77 done:
  78         bkpt    #0
  79
  80         .end
  81