[U-Boot] [PATCH v2 5/5] doc/README.vxworks: add a document describing the new VxWorks boot interface

[Miao Yan]

Signed-off-by: Miao Yan <miao.yan at windriver.com>
---
Changes for v2: none

 doc/README.vxworks |   34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)
 create mode 100644 doc/README.vxworks

diff --git a/doc/README.vxworks b/doc/README.vxworks
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+From VxWorks 6.9+ (not include 6.9), VxWorks starts adopting device tree as its hardware
+decription mechansim (for PowerPC and ARM), thus requiring boot interface changes.
+This section will describe the new interface.
+
+For PowerPC, the calling convention of the new VxWorks entry point conforms to the ePAPR standard[1],
+which is shown below (see ePAPR for more details):
+
+    void (*kernel_entry)(ulong fdt_addr,
+              ulong r4 /* 0 */, ulong r5 /* 0 */,
+              ulong r6 /* EPAPR_MAGIC */
+              ulong r7 /* boot IMA */,
+              ulong r8 /* 0 */, ulong r9 /* 0 */)
+
+For ARM, the calling convention is show below:
+
+    void (*kernel_entry)(void *fdt_addr)
+
+When booting new VxWorks kernel (uImage format), the parameters passed to bootm is like below:
+
+    bootm <kernel image address> - <device tree address>
+
+for example, booting p2020rdb kernel: (kernel is placed at address 0x1000000 and device tree blob
+is places at address 0xf000000)
+
+    setenv bootargs "gei(0,0)....."
+    tftp 0x1000000 vxWorks.uboot
+    tftp 0xf000000 p2020rdb.dtb
+    bootm 0x1000000 - 0xf000000
+
+The second parameter to bootm is always '-' for VxWorks (VxWorks kernel doesn't make use of initrd)
+
+The bootvx command still works as it was for older kernels.
+
+[1] www.power.org
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1.7.9.5