1 * Spreadtrum Pin Controller
2
3 The Spreadtrum pin controller are organized in 3 blocks (types).
4
5 The first block comprises some global control registers, and each
6 register contains several bit fields with one bit or several bits
7 to configure for some global common configuration, such as domain
8 pad driving level, system control select and so on ("domain pad
9 driving level": One pin can output 3.0v or 1.8v, depending on the
10 related domain pad driving selection, if the related domain pad
11 select 3.0v, then the pin can output 3.0v. "system control" is used
12 to choose one function (like: UART0) for which system, since we
13 have several systems (AP/CP/CM4) on one SoC.).
14
15 There are too much various configuration that we can not list all
16 of them, so we can not make every Spreadtrum-special configuration
17 as one generic configuration, and maybe it will add more strange
18 global configuration in future. Then we add one "sprd,control" to
19 set these various global control configuration, and we need use
20 magic number for this property.
21
22 Moreover we recognise every fields comprising one bit or several
23 bits in one global control register as one pin, thus we should
24 record every pin's bit offset, bit width and register offset to
25 configure this field (pin).
26
27 The second block comprises some common registers which have unified
28 register definition, and each register described one pin is used
29 to configure the pin sleep mode, function select and sleep related
30 configuration.
31
32 Now we have 4 systems for sleep mode on SC9860 SoC: AP system,
33 PUBCP system, TGLDSP system and AGDSP system. And the pin sleep
34 related configuration are:
35 - input-enable
36 - input-disable
37 - output-high
38 - output-low
39 - bias-pull-up
40 - bias-pull-down
41
42 In some situation we need set the pin sleep mode and pin sleep related
43 configuration, to set the pin sleep related configuration automatically
44 by hardware when the system specified by sleep mode goes into deep
45 sleep mode. For example, if we set the pin sleep mode as PUBCP_SLEEP
46 and set the pin sleep related configuration as "input-enable", which
47 means when PUBCP system goes into deep sleep mode, this pin will be set
48 input enable automatically.
49
50 Moreover we can not use the "sleep" state, since some systems (like:
51 PUBCP system) do not run linux kernel OS (only AP system run linux
52 kernel on SC9860 platform), then we can not select "sleep" state
53 when the PUBCP system goes into deep sleep mode. Thus we introduce
54 "sprd,sleep-mode" property to set pin sleep mode.
55
56 The last block comprises some misc registers which also have unified
57 register definition, and each register described one pin is used to
58 configure drive strength, pull up/down and so on. Especially for pull
59 up, we have two kind pull up resistor: 20K and 4.7K.
60
61 Required properties for Spreadtrum pin controller:
62 - compatible: "sprd,<soc>-pinctrl"
63 Please refer to each sprd,<soc>-pinctrl.txt binding doc for supported SoCs.
64 - reg: The register address of pin controller device.
65 - pins : An array of pin names.
66
67 Optional properties:
68 - function: Specified the function name.
69 - drive-strength: Drive strength in mA.
70 - input-schmitt-disable: Enable schmitt-trigger mode.
71 - input-schmitt-enable: Disable schmitt-trigger mode.
72 - bias-disable: Disable pin bias.
73 - bias-pull-down: Pull down on pin.
74 - bias-pull-up: Pull up on pin.
75 - input-enable: Enable pin input.
76 - input-disable: Enable pin output.
77 - output-high: Set the pin as an output level high.
78 - output-low: Set the pin as an output level low.
79 - sleep-hardware-state: Indicate these configs in this state are sleep related.
80 - sprd,control: Control values referring to databook for global control pins.
81 - sprd,sleep-mode: Sleep mode selection.
82
83 Please refer to each sprd,<soc>-pinctrl.txt binding doc for supported values.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.