mirror of
https://github.com/AsahiLinux/u-boot
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64 lines
1.9 KiB
Text
64 lines
1.9 KiB
Text
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Building SPL/U-Boot for xea board
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=================================
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Setup environment, configure and build, e.g. by:
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$ make imx28_xea_defconfig
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$ make -j4 u-boot.sb u-boot.img
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Now you should see u-boot.sb and u-boot.img files in the build directory.
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Booting
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=======
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The boot ROM loads SPL from SPI NOR flash into SRAM. SPL configures
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DRAM and loads either a Linux kernel (falcon mode) or, if the rescue
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pin is asserted, the main U-Boot. Both kernel and U-Boot reside in
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eMMC boot partition 0. For redundancy, a copy of U-Boot is also
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stored in SPI flash. If a valid kernel image is not found, U-Boot is
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loaded from eMMC or, if this fails, SPI flash.
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Boot area layout
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----------------
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SPI NOR
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Offset Function File
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------------------------------------------
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0x00000000 SPL u-boot.sb
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0x00010000 U-Boot u-boot.img
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0x00080000 Environment
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eMMC
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Offset Function File
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------------------------------------------
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0x00000000 U-Boot u-boot.img
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0x00080000 Devicetree imx28-bttc.dtb
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0x00100000 Kernel uImage
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Falcon mode
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===========
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In falcon mode, the default, SPL loads the kernel and devicetree
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directly. For this to work, the stored devicetree must include
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correct "memory" and "chosen" nodes as these are not updated by SPL
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before booting the kernel.
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Updating from U-Boot
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====================
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The default U-Boot environment includes command sequences to update
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SPL, U-Boot, and kernel over TFTP. These are as follows:
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- update_spl: writes u-boot.sb to SPI NOR
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- update_uboot: writes u-boot.img to eMMC and SPI NOR
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- update_kernel: writes kernel and devicetree to eMMC
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They can be invoked at the U-Boot prompt using the "run" command,
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e.g. "run update_spl" to update the SPL.
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These update commands download the above-named files from the
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${hostname} directory on the server provided by DHCP.
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