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exynos_thermal_emulation.rst

exynos_thermal_emulation.rst 2.2 KB
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  1. =====================
    2. 

  2. Exynos Emulation Mode
    3. 

  3. =====================
    4. 

  4. 

  5. Copyright (C) 2012 Samsung Electronics
    6. 

  6. 

  7. Written by Jonghwa Lee <[email protected]>
    8. 

  8. 

  9. Description
    10. 

  10. -----------
    11. 

  11. 

  12. Exynos 4x12 (4212, 4412) and 5 series provide emulation mode for thermal
    13. 

  13. management unit. Thermal emulation mode supports software debug for
    14. 

  14. TMU's operation. User can set temperature manually with software code
    15. 

  15. and TMU will read current temperature from user value not from sensor's
    16. 

  16. value.
    17. 

  17. 

  18. Enabling CONFIG_THERMAL_EMULATION option will make this support
    19. 

  19. available. When it's enabled, sysfs node will be created as
    20. 

  20. /sys/devices/virtual/thermal/thermal_zone'zone id'/emul_temp.
    21. 

  21. 

  22. The sysfs node, 'emul_node', will contain value 0 for the initial state.
    23. 

  23. When you input any temperature you want to update to sysfs node, it
    24. 

  24. automatically enable emulation mode and current temperature will be
    25. 

  25. changed into it.
    26. 

  26. 

  27. (Exynos also supports user changeable delay time which would be used to
    28. 

  28. delay of changing temperature. However, this node only uses same delay
    29. 

  29. of real sensing time, 938us.)
    30. 

  30. 

  31. Exynos emulation mode requires synchronous of value changing and
    32. 

  32. enabling. It means when you want to update the any value of delay or
    33. 

  33. next temperature, then you have to enable emulation mode at the same
    34. 

  34. time. (Or you have to keep the mode enabling.) If you don't, it fails to
    35. 

  35. change the value to updated one and just use last succeessful value
    36. 

  36. repeatedly. That's why this node gives users the right to change
    37. 

  37. termerpature only. Just one interface makes it more simply to use.
    38. 

  38. 

  39. Disabling emulation mode only requires writing value 0 to sysfs node.
    40. 

  40. 

  41. ::
    42. 

  42. 

  43. 

  44.   TEMP	120 |
    45. 

  45. 	    |
    46. 

  46. 	100 |
    47. 

  47. 	    |
    48. 

  48. 	 80 |
    49. 

  49. 	    |				 +-----------
    50. 

  50. 	 60 |      			 |	    |
    51. 

  51. 	    |		   +-------------|          |
    52. 

  52. 	 40 |              |         	 |          |
    53. 

  53. 	    |		   |		 |          |
    54. 

  54. 	 20 |		   |		 |          +----------
    55. 

  55. 	    |		   |		 |          |          |
    56. 

  56. 	  0 |______________|_____________|__________|__________|_________
    57. 

  57. 		   A		 A	    A		       A     TIME
    58. 

  58. 		   |<----->|	 |<----->|  |<----->|	       |
    59. 

  59. 		   | 938us |  	 |	 |  |       |          |
    60. 

  60.   emulation   : 0  50	   |  	 70      |  20      |          0
    61. 

  61.   current temp:   sensor   50		 70         20	      sensor
    62.