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Paul Cercueil authored
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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