Vybrid Cortex-M4 mini boot loader for Linux
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Vybrid Cortex-M4 mini boot loader for Linux

This utility helps to boot a (non-MMU) Linux image on the Cortex-M4 CPU of the Freescale Vybrid SoC. The device tree enabled Linux ARM kernels expect a pointer to the device tree binary in the CPU register r2. However, on Vybrid we use the Linux running on the main CPU, the Cortex-A5, to start the secondary Cortex-M4 CPU. The m4boot utility helps archiving this, however since it is running on a different CPU, it can't write the r2 register of the Cortex-M4. This mini boot loader helps the m4boot utility doingt his, by simply moving the SoC specific boot argument pointer from SRC_GPR3 to the CPU's r2 register.

The binary output is part of the m4boot repository. The m4boot utility incorporates the utility and loads it automatically to the appropriate palce.