Merge tag 'mips_5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux

Pull MIPS updates from Paul Burton:
 "Main MIPS changes:

   - boot_mem_map is removed, providing a nice cleanup made possible by
     the recent removal of bootmem.

   - Some fixes to atomics, in general providing compiler barriers for
     smp_mb__{before,after}_atomic plus fixes specific to Loongson CPUs
     or MIPS32 systems using cmpxchg64().

   - Conversion to the new generic VDSO infrastructure courtesy of
     Vincenzo Frascino.

   - Removal of undefined behavior in set_io_port_base(), fixing the
     behavior of some MIPS kernel configurations when built with recent
     clang versions.

   - Initial MIPS32 huge page support, functional on at least Ingenic
     SoCs.

   - pte_special() is now supported for some configurations, allowing
     among other things generic fast GUP to be used.

   - Miscellaneous fixes & cleanups.

  And platform specific changes:

   - Major improvements to Ingenic SoC support from Paul Cercueil,
     mostly enabled by the inclusion of the new TCU (timer-counter unit)
     drivers he's spent a very patient year or so working on. Plus some
     fixes for X1000 SoCs from Zhou Yanjie.

   - Netgear R6200 v1 systems are now supported by the bcm47xx platform.

   - DT updates for BMIPS, Lantiq & Microsemi Ocelot systems"

* tag 'mips_5.4' of git://git.kernel.org/pub/scm/linux/kernel/git/mips/linux: (89 commits)
  MIPS: Detect bad _PFN_SHIFT values
  MIPS: Disable pte_special() for MIPS32 with RiXi
  MIPS: ralink: deactivate PCI support for SOC_MT7621
  mips: compat: vdso: Use legacy syscalls as fallback
  MIPS: Drop Loongson _CACHE_* definitions
  MIPS: tlbex: Remove cpu_has_local_ebase
  MIPS: tlbex: Simplify r3k check
  MIPS: Select R3k-style TLB in Kconfig
  MIPS: PCI: refactor ioc3 special handling
  mips: remove ioremap_cachable
  mips/atomic: Fix smp_mb__{before,after}_atomic()
  mips/atomic: Fix loongson_llsc_mb() wreckage
  mips/atomic: Fix cmpxchg64 barriers
  MIPS: Octeon: remove duplicated include from dma-octeon.c
  firmware: bcm47xx_nvram: Allow COMPILE_TEST
  firmware: bcm47xx_nvram: Correct size_t printf format
  MIPS: Treat Loongson Extensions as ASEs
  MIPS: Remove dev_err() usage after platform_get_irq()
  MIPS: dts: mscc: describe the PTP ready interrupt
  MIPS: dts: mscc: describe the PTP register range
  ...

2 files changed, 77 insertions, 3 deletions

diff --git a/Documentation/mips/index.rst b/Documentation/mips/index.rst
index fd9023c8a89f..a93c2f65884c 100644
--- a/Documentation/mips/index.rst
+++ b/Documentation/mips/index.rst
@@ -1,11 +1,14 @@
 .. SPDX-License-Identifier: GPL-2.0
 
-=================
-MIPS architecture
-=================
+===========================
+MIPS-specific Documentation
+===========================
 
 .. toctree::
    :maxdepth: 2
+   :numbered:
+
+   ingenic-tcu
 
    au1xxx_ide
 
diff --git a/Documentation/mips/ingenic-tcu.rst b/Documentation/mips/ingenic-tcu.rst
new file mode 100644
index 000000000000..c4ef4c45aade
--- /dev/null
+++ b/Documentation/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 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/mfd/ingenic,tcu.txt.