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author | Costa Shulyupin <costa.shul@redhat.com> | 2023-07-25 07:38:03 +0300 |
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committer | Jonathan Corbet <corbet@lwn.net> | 2023-08-18 20:03:52 +0300 |
commit | ec62a746b65363f6078fb1eefc7faffe1a4cdc38 (patch) | |
tree | f942f375b8ea431c3e7e0bf297b2e7a4685f295b /Documentation/arch/mips | |
parent | 51712e49b434950b6317188f88696556c277b10d (diff) | |
download | linux-ec62a746b65363f6078fb1eefc7faffe1a4cdc38.tar.xz |
docs: move mips under arch
and fix all in-tree references.
Architecture-specific documentation is being moved into Documentation/arch/
as a way of cleaning up the top-level documentation directory and making
the docs hierarchy more closely match the source hierarchy.
Signed-off-by: Costa Shulyupin <costa.shul@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230725043835.2249678-1-costa.shul@redhat.com
Diffstat (limited to 'Documentation/arch/mips')
-rw-r--r-- | Documentation/arch/mips/booting.rst | 28 | ||||
-rw-r--r-- | Documentation/arch/mips/features.rst | 3 | ||||
-rw-r--r-- | Documentation/arch/mips/index.rst | 21 | ||||
-rw-r--r-- | Documentation/arch/mips/ingenic-tcu.rst | 71 |
4 files changed, 123 insertions, 0 deletions
diff --git a/Documentation/arch/mips/booting.rst b/Documentation/arch/mips/booting.rst new file mode 100644 index 000000000000..7c18a4eab48b --- /dev/null +++ b/Documentation/arch/mips/booting.rst @@ -0,0 +1,28 @@ +.. SPDX-License-Identifier: GPL-2.0 + +BMIPS DeviceTree Booting +------------------------ + + Some bootloaders only support a single entry point, at the start of the + kernel image. Other bootloaders will jump to the ELF start address. + Both schemes are supported; CONFIG_BOOT_RAW=y and CONFIG_NO_EXCEPT_FILL=y, + so the first instruction immediately jumps to kernel_entry(). + + Similar to the arch/arm case (b), a DT-aware bootloader is expected to + set up the following registers: + + a0 : 0 + + a1 : 0xffffffff + + a2 : Physical pointer to the device tree block (defined in chapter + II) in RAM. The device tree can be located anywhere in the first + 512MB of the physical address space (0x00000000 - 0x1fffffff), + aligned on a 64 bit boundary. + + Legacy bootloaders do not use this convention, and they do not pass in a + DT block. In this case, Linux will look for a builtin DTB, selected via + CONFIG_DT_*. + + This convention is defined for 32-bit systems only, as there are not + currently any 64-bit BMIPS implementations. diff --git a/Documentation/arch/mips/features.rst b/Documentation/arch/mips/features.rst new file mode 100644 index 000000000000..1973d729b29a --- /dev/null +++ b/Documentation/arch/mips/features.rst @@ -0,0 +1,3 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. kernel-feat:: $srctree/Documentation/features mips diff --git a/Documentation/arch/mips/index.rst b/Documentation/arch/mips/index.rst new file mode 100644 index 000000000000..037f85a08fe3 --- /dev/null +++ b/Documentation/arch/mips/index.rst @@ -0,0 +1,21 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=========================== +MIPS-specific Documentation +=========================== + +.. toctree:: + :maxdepth: 2 + :numbered: + + booting + ingenic-tcu + + features + +.. only:: subproject and html + + Indices + ======= + + * :ref:`genindex` diff --git a/Documentation/arch/mips/ingenic-tcu.rst b/Documentation/arch/mips/ingenic-tcu.rst new file mode 100644 index 000000000000..2ce4cb1314dc --- /dev/null +++ b/Documentation/arch/mips/ingenic-tcu.rst @@ -0,0 +1,71 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=============================================== +Ingenic JZ47xx SoCs Timer/Counter Unit hardware +=============================================== + +The Timer/Counter Unit (TCU) in Ingenic JZ47xx SoCs is a multi-function +hardware block. It features up 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 JZ4760B 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. + +Implementation +============== + +The functionalities of the TCU hardware are spread across multiple drivers: + +=========== ===== +clocks drivers/clk/ingenic/tcu.c +interrupts drivers/irqchip/irq-ingenic-tcu.c +timers drivers/clocksource/ingenic-timer.c +OST drivers/clocksource/ingenic-ost.c +PWM drivers/pwm/pwm-jz4740.c +watchdog drivers/watchdog/jz4740_wdt.c +=========== ===== + +Because various functionalities of the TCU that belong to different drivers +and frameworks can be controlled from the same registers, all of these +drivers access their registers through the same regmap. + +For more information regarding the devicetree bindings of the TCU drivers, +have a look at Documentation/devicetree/bindings/timer/ingenic,tcu.yaml. |