[U-Boot] [PATCH v4 0/8] x86: qemu: add fw_cfg interface support for qemu-x86 targets

[Miao Yan]

The fw_cfg interface provided by QEMU allow guests to retrieve various information
about the system, e.g. cpu number, variaous firmware data, kernel setup, etc. The
fw_cfg interface can be accessed through 3 IO ports (on x86), using x86 in/out
instructions.

  - 0x510: select configuration items to access
  - 0x511: reading this port will return data selected in 0x510 
  - 0x514: this can be used to detect if DMA interface is available

If fw_cfg DMA interface is available, it can be used to accelerate
accesses.

This patchset adds the following supports for qemu-x86 targets: 

  + the fw_cfg driver itself

  + add a U-Boot command 'fw' to support direct accessing kernel informtion
    from fw_cfg interface, this saves the time of loading them from hard disk or
    network again, through emulated devices.

  + use fw_cfg to get cpu number at runtime, so smp boot no longer relies on
    the cpu node hard-coded in dts files.

Changes in v4:
  - drop [PATCH v3 7/8] and limit maximum supported cpu number
  - chance 'fw load' to take second parameter for initrd load address
  - change default initrd load address for qemu-x86

Miao Yan (8):
  x86: qemu: add fw_cfg support
  x86: qemu: add a cpu uclass driver for qemu target
  x86: fix a typo in function name
  x86: use actual CPU number for allocating memory
  x86: qemu: add qemu_fwcfg_fdt_fixup()
  x86: qemu: fix up cpu node in device tree
  x86: qemu: adjust ramdisk load address
  x86: qemu: add documentaion for the fw_cfg interface

 arch/x86/cpu/mp_init.c           |  12 +-
 arch/x86/cpu/qemu/Makefile       |   2 +-
 arch/x86/cpu/qemu/cpu.c          |  57 +++++++
 arch/x86/cpu/qemu/fw_cfg.c       | 333 +++++++++++++++++++++++++++++++++++++++
 arch/x86/cpu/qemu/fw_cfg.h       | 108 +++++++++++++
 arch/x86/cpu/qemu/qemu.c         |   7 +
 arch/x86/dts/qemu-x86_i440fx.dts |  19 +--
 arch/x86/dts/qemu-x86_q35.dts    |  19 +--
 doc/README.x86                   |  35 +++-
 include/configs/qemu-x86.h       |  13 ++
 10 files changed, 559 insertions(+), 46 deletions(-)
 create mode 100644 arch/x86/cpu/qemu/cpu.c
 create mode 100644 arch/x86/cpu/qemu/fw_cfg.c
 create mode 100644 arch/x86/cpu/qemu/fw_cfg.h

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1.9.1