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97689a1a3f
Add documentation about the Timer/Counter Unit (TCU) present in the
Ingenic JZ47xx SoCs.
The Timer/Counter Unit (TCU) in Ingenic JZ47xx SoCs is a multi-function
hardware block. It features up to to eight channels, that can be used as
counters, timers, or PWM.
- JZ4725B, JZ4750, JZ4755 only have six TCU channels. The other SoCs all
have eight channels.
- JZ4725B introduced a separate channel, called Operating System Timer
(OST). It is a 32-bit programmable timer. On JZ4770 and above, it is
64-bit.
- Each one of the TCU channels has its own clock, which can be reparented
to three different clocks (pclk, ext, rtc), gated, and reclocked, through
their TCSR register.
* The watchdog and OST hardware blocks also feature a TCSR register with
the same format in their register space.
* The TCU registers used to gate/ungate can also gate/ungate the watchdog
and OST clocks.
- Each TCU channel works in one of two modes:
* mode TCU1: channels cannot work in sleep mode, but are easier to
operate.
* mode TCU2: channels can work in sleep mode, but the operation is a bit
more complicated than with TCU1 channels.
- The mode of each TCU channel depends on the SoC used:
* On the oldest SoCs (up to JZ4740), all of the eight channels operate in
TCU1 mode.
* On JZ4725B, channel 5 operates as TCU2, the others operate as TCU1.
* On newest SoCs (JZ4750 and above), channels 1-2 operate as TCU2, the
others operate as TCU1.
- Each channel can generate an interrupt. Some channels share an interrupt
line, some don't, and this changes between SoC versions:
* on older SoCs (JZ4740 and below), channel 0 and channel 1 have their
own interrupt line; channels 2-7 share the last interrupt line.
* On JZ4725B, channel 0 has its own interrupt; channels 1-5 share one
interrupt line; the OST uses the last interrupt line.
* on newer SoCs (JZ4750 and above), channel 5 has its own interrupt;
channels 0-4 and (if eight channels) 6-7 all share one interrupt line;
the OST uses the last interrupt line.
Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Tested-by: Mathieu Malaterre <malat@debian.org>
Tested-by: Artur Rojek <contact@artur-rojek.eu>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-mips@vger.kernel.org
Cc: linux-clk@vger.kernel.org
Cc: od@zcrc.me
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.. The Linux Kernel documentation master file, created by
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sphinx-quickstart on Fri Feb 12 13:51:46 2016.
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You can adapt this file completely to your liking, but it should at least
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contain the root `toctree` directive.
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.. _linux_doc:
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The Linux Kernel documentation
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==============================
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This is the top level of the kernel's documentation tree. Kernel
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documentation, like the kernel itself, is very much a work in progress;
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that is especially true as we work to integrate our many scattered
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documents into a coherent whole. Please note that improvements to the
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documentation are welcome; join the linux-doc list at vger.kernel.org if
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you want to help out.
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Licensing documentation
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-----------------------
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The following describes the license of the Linux kernel source code
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(GPLv2), how to properly mark the license of individual files in the source
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tree, as well as links to the full license text.
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* :ref:`kernel_licensing`
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User-oriented documentation
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---------------------------
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The following manuals are written for *users* of the kernel — those who are
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trying to get it to work optimally on a given system.
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.. toctree::
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:maxdepth: 2
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admin-guide/index
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kbuild/index
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Firmware-related documentation
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------------------------------
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The following holds information on the kernel's expectations regarding the
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platform firmwares.
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.. toctree::
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:maxdepth: 2
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firmware-guide/index
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Application-developer documentation
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-----------------------------------
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The user-space API manual gathers together documents describing aspects of
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the kernel interface as seen by application developers.
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.. toctree::
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:maxdepth: 2
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userspace-api/index
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ioctl/index
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Introduction to kernel development
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----------------------------------
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These manuals contain overall information about how to develop the kernel.
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The kernel community is quite large, with thousands of developers
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contributing over the course of a year. As with any large community,
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knowing how things are done will make the process of getting your changes
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merged much easier.
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.. toctree::
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:maxdepth: 2
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process/index
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dev-tools/index
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doc-guide/index
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kernel-hacking/index
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trace/index
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maintainer/index
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fault-injection/index
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livepatch/index
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Kernel API documentation
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------------------------
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These books get into the details of how specific kernel subsystems work
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from the point of view of a kernel developer. Much of the information here
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is taken directly from the kernel source, with supplemental material added
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as needed (or at least as we managed to add it — probably *not* all that is
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needed).
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.. toctree::
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:maxdepth: 2
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driver-api/index
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core-api/index
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locking/index
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accounting/index
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block/index
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cdrom/index
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ide/index
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fb/index
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fpga/index
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hid/index
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iio/index
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infiniband/index
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leds/index
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media/index
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netlabel/index
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networking/index
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pcmcia/index
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target/index
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timers/index
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watchdog/index
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input/index
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hwmon/index
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gpu/index
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security/index
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sound/index
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crypto/index
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filesystems/index
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vm/index
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bpf/index
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usb/index
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PCI/index
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misc-devices/index
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mic/index
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scheduler/index
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Architecture-specific documentation
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-----------------------------------
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These books provide programming details about architecture-specific
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implementation.
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.. toctree::
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:maxdepth: 2
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sh/index
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arm/index
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arm64/index
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ia64/index
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m68k/index
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mips/index
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riscv/index
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s390/index
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sh/index
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sparc/index
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x86/index
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xtensa/index
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Filesystem Documentation
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------------------------
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The documentation in this section are provided by specific filesystem
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subprojects.
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.. toctree::
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:maxdepth: 2
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filesystems/ext4/index
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Translations
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------------
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.. toctree::
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:maxdepth: 2
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translations/index
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Indices and tables
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==================
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* :ref:`genindex`
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