Based on kernel version 4.13.3. Page generated on 2017-09-23 13:56 EST.
1 Kernel driver for omap HDQ/1-wire module. 2 ======================================== 3 4 Supported chips: 5 ================ 6 HDQ/1-wire controller on the TI OMAP 2430/3430 platforms. 7 8 A useful link about HDQ basics: 9 =============================== 10 http://focus.ti.com/lit/an/slua408a/slua408a.pdf 11 12 Description: 13 ============ 14 The HDQ/1-Wire module of TI OMAP2430/3430 platforms implement the hardware 15 protocol of the master functions of the Benchmark HDQ and the Dallas 16 Semiconductor 1-Wire protocols. These protocols use a single wire for 17 communication between the master (HDQ/1-Wire controller) and the slave 18 (HDQ/1-Wire external compliant device). 19 20 A typical application of the HDQ/1-Wire module is the communication with battery 21 monitor (gas gauge) integrated circuits. 22 23 The controller supports operation in both HDQ and 1-wire mode. The essential 24 difference between the HDQ and 1-wire mode is how the slave device responds to 25 initialization pulse.In HDQ mode, the firmware does not require the host to 26 create an initialization pulse to the slave.However, the slave can be reset by 27 using an initialization pulse (also referred to as a break pulse).The slave 28 does not respond with a presence pulse as it does in the 1-Wire protocol. 29 30 Remarks: 31 ======== 32 The driver (drivers/w1/masters/omap_hdq.c) supports the HDQ mode of the 33 controller. In this mode, as we can not read the ID which obeys the W1 34 spec(family:id:crc), a module parameter can be passed to the driver which will 35 be used to calculate the CRC and pass back an appropriate slave ID to the W1 36 core. 37 38 By default the master driver and the BQ slave i/f 39 driver(drivers/w1/slaves/w1_bq27000.c) sets the ID to 1. 40 Please note to load both the modules with a different ID if required, but note 41 that the ID used should be same for both master and slave driver loading. 42 43 e.g: 44 insmod omap_hdq.ko W1_ID=2 45 inamod w1_bq27000.ko F_ID=2 46 47 The driver also supports 1-wire mode. In this mode, there is no need to 48 pass slave ID as parameter. The driver will auto-detect slaves connected 49 to the bus using SEARCH_ROM procedure. 1-wire mode can be selected by 50 setting "ti,mode" property to "1w" in DT (see 51 Documentation/devicetree/bindings/w1/omap-hdq.txt for more details). 52 By default driver is in HDQ mode.