Merge remote-tracking branch 'remotes/pmaydell/tags/pull-target-arm-20210901' into staging

 * Refactor M-profile systick to use Clocks instead of system_clock_scale global
 * clock: Provide builtin multiplier/divider
 * Add A64FX processor model
 * Enable MVE emulation in Cortex-M55
 * hw: Add compat machines for 6.2
 * hw/intc/arm_gicv3: Replace mis-used MEMTX_* constants by booleans
 * hw/arm/raspi: Remove deprecated raspi2/raspi3 aliases

# gpg: Signature made Wed 01 Sep 2021 11:35:57 BST
# gpg:                using RSA key E1A5C593CD419DE28E8315CF3C2525ED14360CDE
# gpg:                issuer "peter.maydell@linaro.org"
# gpg: Good signature from "Peter Maydell <peter.maydell@linaro.org>" [ultimate]
# gpg:                 aka "Peter Maydell <pmaydell@gmail.com>" [ultimate]
# gpg:                 aka "Peter Maydell <pmaydell@chiark.greenend.org.uk>" [ultimate]
# Primary key fingerprint: E1A5 C593 CD41 9DE2 8E83  15CF 3C25 25ED 1436 0CDE

* remotes/pmaydell/tags/pull-target-arm-20210901: (51 commits)
  arm: Remove system_clock_scale global
  hw/timer/stellaris-gptm: Use Clock input instead of system_clock_scale
  hw/arm/stellaris: Split stellaris-gptm into its own file
  hw/arm/stellaris: Fix code style issues in GPTM code
  hw/timer/armv7m_systick: Use clock inputs instead of system_clock_scale
  hw/arm/msf2-soc: Wire up refclk
  hw/arm/msf2: Use Clock input to MSF2_SOC instead of m3clk property
  hw/arm/msf2_soc: Don't allocate separate MemoryRegions
  hw/arm/stellaris: Wire sysclk up to armv7m
  hw/arm/stellaris: split stellaris_sys_init()
  hw/arm/nrf51: Wire up sysclk
  hw/arm/stm32vldiscovery: Delete trailing blank line
  hw/arm/stm32f405: Wire up sysclk and refclk
  hw/arm/stm32f205: Wire up sysclk and refclk
  hw/arm/stm32f100: Wire up sysclk and refclk
  hw/arm: Don't allocate separate MemoryRegions in stm32 SoC realize
  clock: Provide builtin multiplier/divider
  hw/arm/mps2.c: Connect up armv7m clocks
  armsse: Wire up systick cpuclk clock
  hw/arm/armv7m: Create input clocks
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 23 insertions, 0 deletions

diff --git a/docs/devel/clocks.rst b/docs/devel/clocks.rst
index 956bd147ea..675fbeb6ab 100644
--- a/docs/devel/clocks.rst
+++ b/docs/devel/clocks.rst
@@ -260,6 +260,29 @@ clocks get the new clock period value: *Clock 2*, *Clock 3* and *Clock 4*.
 It is not possible to disconnect a clock or to change the clock connection
 after it is connected.
 
+Clock multiplier and divider settings
+-------------------------------------
+
+By default, when clocks are connected together, the child
+clocks run with the same period as their source (parent) clock.
+The Clock API supports a built-in period multiplier/divider
+mechanism so you can configure a clock to make its children
+run at a different period from its own. If you call the
+``clock_set_mul_div()`` function you can specify the clock's
+multiplier and divider values. The children of that clock
+will all run with a period of ``parent_period * multiplier / divider``.
+For instance, if the clock has a frequency of 8MHz and you set its
+multiplier to 2 and its divider to 3, the child clocks will run
+at 12MHz.
+
+You can change the multiplier and divider of a clock at runtime,
+so you can use this to model clock controller devices which
+have guest-programmable frequency multipliers or dividers.
+
+Note that ``clock_set_mul_div()`` does not automatically call
+``clock_propagate()``. If you make a runtime change to the
+multiplier or divider you must call clock_propagate() yourself.
+
 Unconnected input clocks
 ------------------------