doc: usage: Convert README.vxworks to reST

This converts the existing README.vxworks to reST, and puts it under
the doc/usage/os directory.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>

2 files changed, 127 insertions, 0 deletions

diff --git a/doc/usage/index.rst b/doc/usage/index.rst
index 5bfe31a496..a16deee145 100644
--- a/doc/usage/index.rst
+++ b/doc/usage/index.rst
@@ -53,3 +53,11 @@ Shell commands
    cmd/true
    cmd/ums
    cmd/wdt
+
+Booting OS
+----------
+
+.. toctree::
+   :maxdepth: 1
+
+   os/vxworks
diff --git a/doc/usage/os/vxworks.rst b/doc/usage/os/vxworks.rst
new file mode 100644
index 0000000000..184042f408
--- /dev/null
+++ b/doc/usage/os/vxworks.rst
@@ -0,0 +1,119 @@
+.. SPDX-License-Identifier: GPL-2.0+
+.. Copyright (C) 2013, Miao Yan <miao.yan@windriver.com>
+.. Copyright (C) 2015-2018, Bin Meng <bmeng.cn@gmail.com>
+.. Copyright (C) 2019, Lihua Zhao <lihua.zhao@windriver.com>
+
+VxWorks
+=======
+
+This document describes the information about U-Boot loading VxWorks kernel.
+
+Status
+------
+U-Boot supports loading VxWorks kernels via 'bootvx' and 'bootm' commands.
+For booting old kernels (6.9.x) on PowerPC and ARM, and all kernel versions
+on other architectures, 'bootvx' shall be used. For booting VxWorks 7 kernels
+on PowerPC and ARM, 'bootm' shall be used.
+
+With CONFIG_EFI_LOADER option, it's possible to chain load a VxWorks x86 kernel
+via the UEFI boot loader application for VxWorks loaded by 'bootefi' command.
+
+VxWorks 7 on PowerPC and ARM
+----------------------------
+From VxWorks 7, VxWorks starts adopting device tree as its hardware description
+mechanism (for PowerPC and ARM), thus requiring boot interface changes.
+This section will describe the new interface.
+
+Since VxWorks 7 SR0640 release, VxWorks starts using Linux compatible standard
+DTB for some boards. With that, the exact same bootm flow as used by Linux is
+used, which includes board-specific DTB fix up. To keep backward compatibility,
+only when the least significant bit of flags in bootargs is set, the standard
+DTB will be used. Otherwise it falls back to the legacy bootm flow.
+
+For legacy bootm flow, make sure the least significant bit of flags in bootargs
+is cleared. The calling convention is described below:
+
+For PowerPC, the calling convention of the new VxWorks entry point conforms to
+the ePAPR standard, which is shown below (see ePAPR for more details):
+
+.. code-block:: c
+
+    void (*kernel_entry)(fdt_addr, 0, 0, EPAPR_MAGIC, boot_IMA, 0, 0)
+
+For ARM, the calling convention is shown below:
+
+.. code-block:: c
+
+    void (*kernel_entry)(void *fdt_addr)
+
+When using the Linux compatible standard DTB, the calling convention of VxWorks
+entry point is exactly the same as the Linux kernel.
+
+When booting a VxWorks 7 kernel (uImage format), the parameters passed to bootm
+is like below::
+
+    bootm <kernel image address> - <device tree address>
+
+VxWorks bootline
+----------------
+When using 'bootvx', the kernel bootline must be prepared by U-Boot at a
+board-specific address before loading VxWorks. U-Boot supplies its address
+via "bootaddr" environment variable. To check where the bootline should be
+for a specific board, go to the VxWorks BSP for that board, and look for a
+parameter called BOOT_LINE_ADRS. Assign its value to "bootaddr". A typical
+value for "bootaddr" on an x86 board is 0x101200.
+
+If a "bootargs" variable is defined, its content will be copied to the memory
+location pointed by "bootaddr" as the kernel bootline. If "bootargs" is not
+there, command 'bootvx' can construct a valid bootline using the following
+environments variables: bootdev, bootfile, ipaddr, netmask, serverip,
+gatewayip, hostname, othbootargs.
+
+When using 'bootm', just define "bootargs" in the environment and U-Boot will
+handle bootline fix up for the kernel dtb automatically.
+
+When using 'bootefi' to chain load an x86 kernel, the UEFI boot loader
+application for VxWorks takes care of the kernel bootline preparation.
+
+Serial console
+--------------
+It's very common that VxWorks BSPs configure a different baud rate for the
+serial console from what is being used by U-Boot. For example, VxWorks tends
+to use 9600 as the default baud rate on all x86 BSPs while U-Boot uses 115200.
+Please configure both U-Boot and VxWorks to use the same baud rate, or it may
+look like VxWorks hangs somewhere as nothing outputs on the serial console.
+
+x86-specific information
+------------------------
+Before direct loading an x86 kernel via 'bootvx', one additional environment
+variable need to be provided. This is "vx_phys_mem_base", which represent the
+physical memory base address of VxWorks.
+
+Check VxWorks kernel configuration to look for LOCAL_MEM_LOCAL_ADRS. For
+VxWorks 7, this is normally a virtual address and you need find out its
+corresponding physical address and assign its value to "vx_phys_mem_base".
+
+For boards on which ACPI is not supported by U-Boot yet, VxWorks kernel must
+be configured to use MP table and virtual wire interrupt mode. This requires
+INCLUDE_MPTABLE_BOOT_OP and INCLUDE_VIRTUAL_WIRE_MODE to be included in a
+VxWorks kernel configuration.
+
+Both 32-bit x86 and 64-bit x64 kernels can be loaded.
+
+There are two types of graphics console drivers in VxWorks. One is the 80x25
+VGA text mode driver. The other one is the EFI console bitmapped graphics mode
+driver. To make these drivers function, U-Boot needs to load and run the VGA
+BIOS of the graphics card first.
+
+    - If the kernel is configured with 80x25 VGA text mode driver,
+      CONFIG_FRAMEBUFFER_SET_VESA_MODE must be unset in U-Boot.
+    - If the kernel is configured with bitmapped graphics mode driver,
+      CONFIG_FRAMEBUFFER_SET_VESA_MODE need remain set but care must be taken
+      at which VESA mode is to be set. The supported pixel format is 32-bit
+      RGBA, hence the available VESA mode can only be one of the following:
+
+        * FRAMEBUFFER_VESA_MODE_10F
+        * FRAMEBUFFER_VESA_MODE_112
+        * FRAMEBUFFER_VESA_MODE_115
+        * FRAMEBUFFER_VESA_MODE_118
+        * FRAMEBUFFER_VESA_MODE_11B