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hdq: documentation for OMAP HDQ
Add a brief document about omap2430/3430 HDQ/1-wire driver.
Signed-off-by: Madhusudhan Chikkature<madhu.cr@ti.com>
Acked-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
authored by
Madhusudhan Chikkature
and committed by
Linus Torvalds
e0a29382
cfbc6190
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Documentation/w1/masters/omap-hdq
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Documentation/w1/masters/omap-hdq
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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/slua408/slua408.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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inamod w1_bq27000.ko F_ID=2
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