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8b83b53a8d
Update the Kconfig entry to have the correct defaults for i.MX7 platforms, and move the existing large comment from imx7_spl.h to doc/imx/common/imx7.txt so that it's not lost. Signed-off-by: Tom Rini <trini@konsulko.com>
23 lines
1.3 KiB
Text
23 lines
1.3 KiB
Text
U-Boot for Freescale i.MX7
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SPL Stack size and location notes
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---------------------------------
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See figure 6-22 in i.MX 7Dual/Solo Reference manuals:
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- IMX7D/S OCRAM free area RAM (OCRAM) is from 0x00910000 to
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0x00946C00.
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- Set the stack at the end of the free area section, at 0x00946BB8.
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- The BOOT ROM loads what they consider the firmware image
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which consists of a 4K header in front of us that contains the IVT, DCD
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and some padding. However, the manual also states that the ROM uses the
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OCRAM_EPCD and OCRAM_PXP areas for itself. While the SPL is free to use
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this range for stack and malloc, the SPL itself must fit below 0x920000,
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or the image will be truncated in at least some boot modes like USB SDP.
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Thus our max size is really 0x00920000 - 0x00912000. If necessary,
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CONFIG_SPL_TEXT_BASE could be moved to 0x00911000 to gain 4KB of space
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for the SPL, but 56KB should be more than enough for the SPL.
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- Pad SPL to 68KB (4KB header + 56KB max size + 8KB extra padding)
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The extra padding could be removed, but this value was used historically
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based on an incorrect CONFIG_SPL_MAX_SIZE definition.
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This allows to write the SPL/U-Boot combination generated with
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u-boot-with-spl.imx directly to a boot media (given that boot media specific
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offset is configured properly).
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