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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-17 16:22:26 -0700 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-09-17 16:22:26 -0700 |
commit | 7c672abc120a55f678e5571ae2ee93f06ca4d7f9 (patch) | |
tree | 7beebc09f9626ca8d5f7df4dded0a553de479323 /Documentation/w1/masters/omap-hdq.rst | |
parent | 1902314157b19754e0ff25b44527654847cfd127 (diff) | |
parent | fe013f8bc160d79c6e33bb66d9bb0cd24949274c (diff) |
Merge tag 'docs-5.4' of git://git.lwn.net/linux
Pull documentation updates from Jonathan Corbet:
"It's a somewhat calmer cycle for docs this time, as the churn of the
mass RST conversion is happily mostly behind us.
- A new document on reproducible builds.
- We finally got around to zapping the documentation for hardware
support that was removed in 2004; one doesn't want to rush these
things.
- The usual assortment of fixes, typo corrections, etc"
* tag 'docs-5.4' of git://git.lwn.net/linux: (67 commits)
Documentation: kbuild: Add document about reproducible builds
docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]
Documentation: Add "earlycon=sbi" to the admin guide
doc:lock: remove reference to clever use of read-write lock
devices.txt: improve entry for comedi (char major 98)
docs: mtd: Update spi nor reference driver
doc: arm64: fix grammar dtb placed in no attributes region
Documentation: sysrq: don't recommend 'S' 'U' before 'B'
mailmap: Update email address for Quentin Perret
docs: ftrace: clarify when tracing is disabled by the trace file
docs: process: fix broken link
Documentation/arm/samsung-s3c24xx: Remove stray U+FEFF character to fix title
Documentation/arm/sa1100/assabet: Fix 'make assabet_defconfig' command
Documentation/arm/sa1100: Remove some obsolete documentation
docs/zh_CN: update Chinese howto.rst for latexdocs making
Documentation: virt: Fix broken reference to virt tree's index
docs: Fix typo on pull requests guide
kernel-doc: Allow anonymous enum
Documentation: sphinx: Don't parse socket() as identifier reference
Documentation: sphinx: Add missing comma to list of strings
...
Diffstat (limited to 'Documentation/w1/masters/omap-hdq.rst')
-rw-r--r-- | Documentation/w1/masters/omap-hdq.rst | 54 |
1 files changed, 54 insertions, 0 deletions
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. |