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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 <jonghwa3.lee@samsung.com>
    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 that value changes and enabling are performed
    32. 

  32. synchronously. This means that when you want to update any value, such as the
    33. 

  33. delay or the next temperature, you must enable emulation mode at the same
    34. 

  34. time (or keep the mode enabled). If you do not, the value will fail to update
    35. 

  35. and the last successful value will continue to be used. For this reason,
    36. 

  36. this node only allows users to change the temperature. Providing a single
    37. 

  37. interface makes it simpler 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.