Home Explore Help
Sign In
GfA
/
linux_kernel
5
0
Fork 0
Files Issues 0 Pull Requests 0 Wiki
Tree: ae65a26dd3
Branches Tags
linux_kernel
/
arch
/
arm
/
lib
/
delay-loop.S

delay-loop.S 1.2 KB
History Raw

1234567891011121314151617181920212223242526272829303132333435363738394041424344454647484950515253545556575859606162 
  1. /*
    2. 

  2.  *  linux/arch/arm/lib/delay.S
    3. 

  3.  *
    4. 

  4.  *  Copyright (C) 1995, 1996 Russell King
    5. 

  5.  *
    6. 

  6.  * This program is free software; you can redistribute it and/or modify
    7. 

  7.  * it under the terms of the GNU General Public License version 2 as
    8. 

  8.  * published by the Free Software Foundation.
    9. 

  9.  */
    10. 

  10. #include <linux/linkage.h>
    11. 

  11. #include <asm/assembler.h>
    12. 

  12. #include <asm/delay.h>
    13. 

  13. 

  14. 		.text
    15. 

  15. 

  16. .LC0:		.word	loops_per_jiffy
    17. 

  17. .LC1:		.word	UDELAY_MULT
    18. 

  18. 

  19. /*
    20. 

  20.  * loops = r0 * HZ * loops_per_jiffy / 1000000
    21. 

  21.  *
    22. 

  22.  * r0  <= 2000
    23. 

  23.  * HZ  <= 1000
    24. 

  24.  */
    25. 

  25. 

  26. ENTRY(__loop_udelay)
    27. 

  27. 		ldr	r2, .LC1
    28. 

  28. 		mul	r0, r2, r0		@ r0 = delay_us * UDELAY_MULT
    29. 

  29. ENTRY(__loop_const_udelay)			@ 0 <= r0 <= 0xfffffaf0
    30. 

  30. 		ldr	r2, .LC0
    31. 

  31. 		ldr	r2, [r2]
    32. 

  32. 		umull	r1, r0, r2, r0		@ r0-r1 = r0 * loops_per_jiffy
    33. 

  33. 		adds	r1, r1, #0xffffffff	@ rounding up ...
    34. 

  34. 		adcs	r0, r0, r0		@ and right shift by 31
    35. 

  35. 		reteq	lr
    36. 

  36. 

  37. 		.align 3
    38. 

  38. 

  39. @ Delay routine
    40. 

  40. ENTRY(__loop_delay)
    41. 

  41. 		subs	r0, r0, #1
    42. 

  42. #if 0
    43. 

  43. 		retls	lr
    44. 

  44. 		subs	r0, r0, #1
    45. 

  45. 		retls	lr
    46. 

  46. 		subs	r0, r0, #1
    47. 

  47. 		retls	lr
    48. 

  48. 		subs	r0, r0, #1
    49. 

  49. 		retls	lr
    50. 

  50. 		subs	r0, r0, #1
    51. 

  51. 		retls	lr
    52. 

  52. 		subs	r0, r0, #1
    53. 

  53. 		retls	lr
    54. 

  54. 		subs	r0, r0, #1
    55. 

  55. 		retls	lr
    56. 

  56. 		subs	r0, r0, #1
    57. 

  57. #endif
    58. 

  58. 		bhi	__loop_delay
    59. 

  59. 		ret	lr
    60. 

  60. ENDPROC(__loop_udelay)
    61. 

  61. ENDPROC(__loop_const_udelay)
    62. 

  62. ENDPROC(__loop_delay)
    63.