tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
1========================
2Kernel driver exynos_tmu
3========================
4
5Supported chips:
6
7* ARM Samsung Exynos4, Exynos5 series of SoC
8
9 Datasheet: Not publicly available
10
11Authors: Donggeun Kim <dg77.kim@samsung.com>
12Authors: Amit Daniel <amit.daniel@samsung.com>
13
14TMU controller Description:
15---------------------------
16
17This driver allows to read temperature inside Samsung Exynos4/5 series of SoC.
18
19The chip only exposes the measured 8-bit temperature code value
20through a register.
21Temperature can be taken from the temperature code.
22There are three equations converting from temperature to temperature code.
23
24The three equations are:
25 1. Two point trimming::
26
27 Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1
28
29 2. One point trimming::
30
31 Tc = T + TI1 - 25
32
33 3. No trimming::
34
35 Tc = T + 50
36
37 Tc:
38 Temperature code, T: Temperature,
39 TI1:
40 Trimming info for 25 degree Celsius (stored at TRIMINFO register)
41 Temperature code measured at 25 degree Celsius which is unchanged
42 TI2:
43 Trimming info for 85 degree Celsius (stored at TRIMINFO register)
44 Temperature code measured at 85 degree Celsius which is unchanged
45
46TMU(Thermal Management Unit) in Exynos4/5 generates interrupt
47when temperature exceeds pre-defined levels.
48The maximum number of configurable threshold is five.
49The threshold levels are defined as follows::
50
51 Level_0: current temperature > trigger_level_0 + threshold
52 Level_1: current temperature > trigger_level_1 + threshold
53 Level_2: current temperature > trigger_level_2 + threshold
54 Level_3: current temperature > trigger_level_3 + threshold
55
56The threshold and each trigger_level are set
57through the corresponding registers.
58
59When an interrupt occurs, this driver notify kernel thermal framework
60with the function exynos_report_trigger.
61Although an interrupt condition for level_0 can be set,
62it can be used to synchronize the cooling action.
63
64TMU driver description:
65-----------------------
66
67The exynos thermal driver is structured as::
68
69 Kernel Core thermal framework
70 (thermal_core.c, step_wise.c, cpufreq_cooling.c)
71 ^
72 |
73 |
74 TMU configuration data -----> TMU Driver <----> Exynos Core thermal wrapper
75 (exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c)
76 (exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h)
77
78a) TMU configuration data:
79 This consist of TMU register offsets/bitfields
80 described through structure exynos_tmu_registers. Also several
81 other platform data (struct exynos_tmu_platform_data) members
82 are used to configure the TMU.
83b) TMU driver:
84 This component initialises the TMU controller and sets different
85 thresholds. It invokes core thermal implementation with the call
86 exynos_report_trigger.
87c) Exynos Core thermal wrapper:
88 This provides 3 wrapper function to use the
89 Kernel core thermal framework. They are exynos_unregister_thermal,
90 exynos_register_thermal and exynos_report_trigger.