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diff --git a/Documentation/w1/masters/omap-hdq.rst b/Documentation/w1/masters/omap-hdq.rst new file mode 100644 index 000000000000..345298a59e50 --- /dev/null +++ b/Documentation/w1/masters/omap-hdq.rst @@ -0,0 +1,54 @@ +======================================== +Kernel driver for omap HDQ/1-wire module +======================================== + +Supported chips: +================ +HDQ/1-wire controller on the TI OMAP 2430/3430 platforms. + +A useful link about HDQ basics: +=============================== +http://focus.ti.com/lit/an/slua408a/slua408a.pdf + +Description: +============ +The HDQ/1-Wire module of TI OMAP2430/3430 platforms implement the hardware +protocol of the master functions of the Benchmark HDQ and the Dallas +Semiconductor 1-Wire protocols. These protocols use a single wire for +communication between the master (HDQ/1-Wire controller) and the slave +(HDQ/1-Wire external compliant device). + +A typical application of the HDQ/1-Wire module is the communication with battery +monitor (gas gauge) integrated circuits. + +The controller supports operation in both HDQ and 1-wire mode. The essential +difference between the HDQ and 1-wire mode is how the slave device responds to +initialization pulse.In HDQ mode, the firmware does not require the host to +create an initialization pulse to the slave.However, the slave can be reset by +using an initialization pulse (also referred to as a break pulse).The slave +does not respond with a presence pulse as it does in the 1-Wire protocol. + +Remarks: +======== +The driver (drivers/w1/masters/omap_hdq.c) supports the HDQ mode of the +controller. In this mode, as we can not read the ID which obeys the W1 +spec(family:id:crc), a module parameter can be passed to the driver which will +be used to calculate the CRC and pass back an appropriate slave ID to the W1 +core. + +By default the master driver and the BQ slave i/f +driver(drivers/w1/slaves/w1_bq27000.c) sets the ID to 1. +Please note to load both the modules with a different ID if required, but note +that the ID used should be same for both master and slave driver loading. + +e.g:: + + insmod omap_hdq.ko W1_ID=2 + inamod w1_bq27000.ko F_ID=2 + +The driver also supports 1-wire mode. In this mode, there is no need to +pass slave ID as parameter. The driver will auto-detect slaves connected +to the bus using SEARCH_ROM procedure. 1-wire mode can be selected by +setting "ti,mode" property to "1w" in DT (see +Documentation/devicetree/bindings/w1/omap-hdq.txt for more details). +By default driver is in HDQ mode. |