| ======================================== |
| 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. |
