[PATCH v6 0/4] MIPS: Remote processor driver

[Matt Redfearn]

The MIPS remote processor driver allows non-Linux firmware to take
control of and execute on one of the systems VPEs, turning the system
into a hybrid of SMP Linux and AMP.

This is useful to allow running bare metal code, or an RTOS, on one or
more CPUs while allowing Linux to continue running on those remaining.

This functionality is conceptually similar to the VPE loader, an arch
specific mechanism which has been in the MIPS Linux kernel since 2005.
This driver is an attempt to make that functionality more standard by
moving it into the remoteproc subsystem.

A system CPU must be offlined from Linux and the driver enabled for that
CPU via the drivers sysfs interface. The remoteproc subsystem then takes
control of the CPU and loads a separate firmware image to it. A full
description is available at [1]. Example firmware images for the driver
and host programs to test them are available at [2].

The first patches in this series lay the groundwork for the driver
before it is added. The last series deprecates the VPE loader.

This functionality is supported on:
- MIPS32r2 devices implementing the MIPS MT ASE for multithreading, such
  as interAptiv.
- MIPS32r6 devices implementing VPs, such as I6400.

Limitations:
- The remoteproc core supports only 32bit ELFs. Therefore it is only
  possible to run 32bit firmware on the remote processor. Also, for
  virtio communication, pointers are passed from the kernel to firmware.
  There can be no mismatch in pointer sizes between the kernel and
  firmware, so this limits the host kernel to 32bit as well.

The functionality has been tested on the Ci40 board which has a 2 core 2
thread interAptiv.

This series is based on v4.11-rc3

[1] http://wiki.prplfoundation.org/w/images/d/df/MIPS_OS_Remote_Processor_Driver_Whitepaper_1.0.9.pdf
[2] https://github.com/MIPS/mips-rproc-example


Changes in v6:
Rebase on Linux 4.11-rc3
Change to set_current_state() as set_task_state has been removed.

Changes in v5:
Depend on !64bit since this driver only works with 32bit kernels
Set mproc->tsk state to TASK_DEAD before freeing it to avoid warning
Flush icache of each carveout so that icache sees latest data written

Changes in v4:
Fix inconsistency of Linux CPU number and VP ID
Have a single mips-rproc device to be parent to each CPU's rproc device.
Support per-device coherence introduced in v4.9
Add a sysfs interface to control the mask of cpus available to rproc

Changes in v3:
Update GIC context saving to use CPU hotplug state machine
Update MIPS remoteproc driver to use CPU hotplug state machine
Remove sysfs interface from MIPS rproc driver, now provided by the core.
Drop patches that Ralf has already merged to mips-next

Changes in v2:
Add dependence on additional patches to mips-gic in commit log
Incorporate changes from Marc Zynger's review:
- Remove CONTEXT_SAVING define.
- Make saved local state a per-cpu variable
- Make gic_save_* static functions when enabled, and do { } while(0)
  otherwise

Lisa Parratt (1):
  MIPS: CPS: Add VP(E) stealing

Matt Redfearn (3):
  irqchip: mips-gic: Add context saving for MIPS_REMOTEPROC
  remoteproc/MIPS: Add a remoteproc driver for MIPS
  MIPS: Deprecate VPE Loader

 Documentation/ABI/testing/sysfs-devices-mips-rproc |  13 +
 arch/mips/Kconfig                                  |  12 +-
 arch/mips/include/asm/smp-cps.h                    |   8 +
 arch/mips/kernel/smp-cps.c                         | 162 +++++-
 arch/mips/kernel/smp.c                             |  12 +
 drivers/irqchip/irq-mips-gic.c                     | 207 ++++++-
 drivers/remoteproc/Kconfig                         |  11 +
 drivers/remoteproc/Makefile                        |   1 +
 drivers/remoteproc/mips_remoteproc.c               | 599 +++++++++++++++++++++
 9 files changed, 1010 insertions(+), 15 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-mips-rproc
 create mode 100644 drivers/remoteproc/mips_remoteproc.c

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2.7.4