1 ======================================== 1 ========================================
2 Kernel driver for omap HDQ/1-wire module 2 Kernel driver for omap HDQ/1-wire module
3 ======================================== 3 ========================================
4 4
5 Supported chips: 5 Supported chips:
6 ================ 6 ================
7 HDQ/1-wire controller on the TI OMAP 2430/3430 7 HDQ/1-wire controller on the TI OMAP 2430/3430 platforms.
8 8
9 A useful link about HDQ basics: 9 A useful link about HDQ basics:
10 =============================== 10 ===============================
11 http://focus.ti.com/lit/an/slua408a/slua408a.p 11 http://focus.ti.com/lit/an/slua408a/slua408a.pdf
12 12
13 Description: 13 Description:
14 ============ 14 ============
15 The HDQ/1-Wire module of TI OMAP2430/3430 plat 15 The HDQ/1-Wire module of TI OMAP2430/3430 platforms implement the hardware
16 protocol of the master functions of the Benchm 16 protocol of the master functions of the Benchmark HDQ and the Dallas
17 Semiconductor 1-Wire protocols. These protocol 17 Semiconductor 1-Wire protocols. These protocols use a single wire for
18 communication between the master (HDQ/1-Wire c 18 communication between the master (HDQ/1-Wire controller) and the slave
19 (HDQ/1-Wire external compliant device). 19 (HDQ/1-Wire external compliant device).
20 20
21 A typical application of the HDQ/1-Wire module 21 A typical application of the HDQ/1-Wire module is the communication with battery
22 monitor (gas gauge) integrated circuits. 22 monitor (gas gauge) integrated circuits.
23 23
24 The controller supports operation in both HDQ 24 The controller supports operation in both HDQ and 1-wire mode. The essential
25 difference between the HDQ and 1-wire mode is 25 difference between the HDQ and 1-wire mode is how the slave device responds to
26 initialization pulse.In HDQ mode, the firmware 26 initialization pulse.In HDQ mode, the firmware does not require the host to
27 create an initialization pulse to the slave.Ho 27 create an initialization pulse to the slave.However, the slave can be reset by
28 using an initialization pulse (also referred t 28 using an initialization pulse (also referred to as a break pulse).The slave
29 does not respond with a presence pulse as it d 29 does not respond with a presence pulse as it does in the 1-Wire protocol.
30 30
31 Remarks: 31 Remarks:
32 ======== 32 ========
33 The driver (drivers/w1/masters/omap_hdq.c) sup 33 The driver (drivers/w1/masters/omap_hdq.c) supports the HDQ mode of the
34 controller. In this mode, as we can not read t 34 controller. In this mode, as we can not read the ID which obeys the W1
35 spec(family:id:crc), a module parameter can be 35 spec(family:id:crc), a module parameter can be passed to the driver which will
36 be used to calculate the CRC and pass back an 36 be used to calculate the CRC and pass back an appropriate slave ID to the W1
37 core. 37 core.
38 38
39 By default the master driver and the BQ slave 39 By default the master driver and the BQ slave i/f
40 driver(drivers/w1/slaves/w1_bq27000.c) sets th 40 driver(drivers/w1/slaves/w1_bq27000.c) sets the ID to 1.
41 Please note to load both the modules with a di 41 Please note to load both the modules with a different ID if required, but note
42 that the ID used should be same for both maste 42 that the ID used should be same for both master and slave driver loading.
43 43
44 e.g:: 44 e.g::
45 45
46 insmod omap_hdq.ko W1_ID=2 46 insmod omap_hdq.ko W1_ID=2
47 insmod w1_bq27000.ko F_ID=2 47 insmod w1_bq27000.ko F_ID=2
48 48
49 The driver also supports 1-wire mode. In this 49 The driver also supports 1-wire mode. In this mode, there is no need to
50 pass slave ID as parameter. The driver will au 50 pass slave ID as parameter. The driver will auto-detect slaves connected
51 to the bus using SEARCH_ROM procedure. 1-wire 51 to the bus using SEARCH_ROM procedure. 1-wire mode can be selected by
52 setting "ti,mode" property to "1w" in DT (see 52 setting "ti,mode" property to "1w" in DT (see
53 Documentation/devicetree/bindings/w1/omap-hdq. 53 Documentation/devicetree/bindings/w1/omap-hdq.txt for more details).
54 By default driver is in HDQ mode. 54 By default driver is in HDQ mode.
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