1* TI - TSC ADC (Touschscreen and analog digital converter)
2~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
3
4Required properties:
5- mfd
6	compatible: Should be
7		"ti,am3359-tscadc" for AM335x/AM437x SoCs
8		"ti,am654-tscadc", "ti,am3359-tscadc" for AM654 SoCs
9- child "tsc"
10	compatible: Should be "ti,am3359-tsc".
11	ti,wires: Wires refer to application modes i.e. 4/5/8 wire touchscreen
12		  support on the platform.
13	ti,x-plate-resistance: X plate resistance
14	ti,coordinate-readouts: The sequencer supports a total of 16
15				programmable steps each step is used to
16				read a single coordinate. A single
17                                readout is enough but multiple reads can
18				increase the quality.
19				A value of 5 means, 5 reads for X, 5 for
20				Y and 2 for Z (always). This utilises 12
21				of the 16 software steps available. The
22				remaining 4 can be used by the ADC.
23	ti,wire-config: Different boards could have a different order for
24			connecting wires on touchscreen. We need to provide an
25			8 bit number where in the 1st four bits represent the
26			analog lines and the next 4 bits represent positive/
27			negative terminal on that input line. Notations to
28			represent the input lines and terminals resoectively
29			is as follows:
30			AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.
31			XP  = 0, XN = 1, YP = 2, YN = 3.
32- child "adc"
33	compatible: Should be
34		    "ti,am3359-adc" for AM335x/AM437x SoCs
35		    "ti,am654-adc", "ti,am3359-adc" for AM654 SoCs
36	ti,adc-channels: List of analog inputs available for ADC.
37			 AIN0 = 0, AIN1 = 1 and so on till AIN7 = 7.
38
39Optional properties:
40- child "tsc"
41	ti,charge-delay: Length of touch screen charge delay step in terms of
42			 ADC clock cycles. Charge delay value should be large
43			 in order to avoid false pen-up events. This value
44			 effects the overall sampling speed, hence need to be
45			 kept as low as possible, while avoiding false pen-up
46			 event. Start from a lower value, say 0x400, and
47			 increase value until false pen-up events are avoided.
48			 The pen-up detection happens immediately after the
49			 charge step, so this does in fact function as a
50			 hardware knob for adjusting the amount of "settling
51			 time".
52
53- child "adc"
54	ti,chan-step-opendelay: List of open delays for each channel of
55				ADC in the order of ti,adc-channels. The
56				value corresponds to the number of ADC
57				clock cycles to wait after applying the
58				step configuration registers and before
59				sending the start of ADC conversion.
60				Maximum value is 0x3FFFF.
61       ti,chan-step-sampledelay: List of sample delays for each channel
62				  of ADC in the order of ti,adc-channels.
63				  The value corresponds to the number of
64				  ADC clock cycles to sample (to hold
65				  start of conversion high).
66				  Maximum value is 0xFF.
67       ti,chan-step-avg: Number of averages to be performed for each
68			  channel of ADC. If average is 16 then input
69			  is sampled 16 times and averaged to get more
70			  accurate value. This increases the time taken
71			  by ADC to generate a sample. Valid range is 0
72			  average to 16 averages. Maximum value is 16.
73
74Example:
75	tscadc: tscadc@44e0d000 {
76		compatible = "ti,am3359-tscadc";
77		tsc {
78			ti,wires = <4>;
79			ti,x-plate-resistance = <200>;
80			ti,coordiante-readouts = <5>;
81			ti,wire-config = <0x00 0x11 0x22 0x33>;
82			ti,charge-delay = <0x400>;
83		};
84
85		adc {
86			ti,adc-channels = <4 5 6 7>;
87			ti,chan-step-opendelay = <0x098 0x3ffff 0x098 0x0>;
88			ti,chan-step-sampledelay = <0xff 0x0 0xf 0x0>;
89			ti,chan-step-avg = <16 2 4 8>;
90		};
91	}
92