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