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start.S

start.S 1.5 KB
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  1. /*
    2. 

  2.  * Copyright (c) 2021-2023 HPMicro
    3. 

  3.  *
    4. 

  4.  * SPDX-License-Identifier: BSD-3-Clause
    5. 

  5.  *
    6. 

  6.  */
    7. 

  7.  #include <rtconfig.h>
    8. 

  8.  #include "hpm_csr_regs.h"
    9. 

  9.     .section .start, "ax"
    10. 

  10. 

  11.     .global _start
    12. 

  12.     .type _start,@function
    13. 

  13. 

  14. _start:
    15. 

  15.     /* Initialize global pointer */
    16. 

  16.     .option push
    17. 

  17.     .option norelax
    18. 

  18.     la gp, __global_pointer$
    19. 

  19.     la tp, __thread_pointer
    20. 

  20.     .option pop
    21. 

  21. 

  22. #ifdef __riscv_flen
    23. 

  23.     /* Enable FPU */
    24. 

  24.     li t0, CSR_MSTATUS_FS_MASK
    25. 

  25.     csrrs t0, mstatus, t0
    26. 

  26. 

  27.     /* Initialize FCSR */
    28. 

  28.     fscsr zero
    29. 

  29. #endif
    30. 

  30. 

  31. #ifdef INIT_EXT_RAM_FOR_DATA
    32. 

  32.     la t0, _stack_in_dlm
    33. 

  33.     mv sp, t0
    34. 

  34.     call _init_ext_ram
    35. 

  35. #endif
    36. 

  36. 

  37.     /* Initialize stack pointer */
    38. 

  38.     la t0, _stack
    39. 

  39.     mv sp, t0
    40. 

  40. 

  41. #ifdef __nds_execit
    42. 

  42.     /* Initialize EXEC.IT table */
    43. 

  43.     la t0, _ITB_BASE_
    44. 

  44.     csrw uitb, t0
    45. 

  45. #endif
    46. 

  46. 

  47. #ifdef __riscv_flen
    48. 

  48.     /* Enable FPU */
    49. 

  49.     li t0, CSR_MSTATUS_FS_MASK
    50. 

  50.     csrrs t0, mstatus, t0
    51. 

  51. 

  52.     /* Initialize FCSR */
    53. 

  53.     fscsr zero
    54. 

  54. #endif
    55. 

  55.     /* Disable Vector mode */
    56. 

  56.     csrci CSR_MMISC_CTL, 2
    57. 

  57.     /* Initialize trap_entry base */
    58. 

  58.     la t0, SW_handler
    59. 

  59.     csrw mtvec, t0
    60. 

  60. 

  61. 

  62.     /* System reset handler */
    63. 

  63.     call reset_handler
    64. 

  64. 

  65.     /* Infinite loop, if returned accidently */
    66. 

  66. 1:    j 1b
    67. 

  67. 

  68.     .weak nmi_handler
    69. 

  69. nmi_handler:
    70. 

  70. 1:    j 1b
    71. 

  71. 

  72.     .global default_irq_handler
    73. 

  73.     .weak default_irq_handler
    74. 

  74.     .align 2
    75. 

  75. default_irq_handler:
    76. 

  76. 1:    j 1b
    77. 

  77. 

  78.     .macro IRQ_HANDLER irq
    79. 

  79.     .weak default_isr_\irq
    80. 

  80.     .set default_isr_\irq, default_irq_handler
    81. 

  81.     .long default_isr_\irq
    82. 

  82.     .endm
    83. 

  83. 

  84. #include "vectors.S"
    85.