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Diffstat (limited to 'docs/components/romlib-design.rst')
| -rw-r--r-- | docs/components/romlib-design.rst | 22 |
1 files changed, 14 insertions, 8 deletions
diff --git a/docs/components/romlib-design.rst b/docs/components/romlib-design.rst index e0a028e46..d34b3cc58 100644 --- a/docs/components/romlib-design.rst +++ b/docs/components/romlib-design.rst @@ -115,21 +115,27 @@ Memory impact ~~~~~~~~~~~~~ Using library at ROM will modify the memory layout of the BL images: + - The ROM library needs a page aligned RAM section to hold the RW data. This - section is defined by the ROMLIB_RW_BASE and ROMLIB_RW_END macros. - On Arm platforms a section of 1 page (0x1000) is allocated at the top of SRAM. - This will have for effect to shift down all the BL images by 1 page. + section is defined by the ROMLIB_RW_BASE and ROMLIB_RW_END macros. + On Arm platforms a section of 1 page (0x1000) is allocated at the top of SRAM. + This will have for effect to shift down all the BL images by 1 page. + - Depending on the functions moved to the ROM library, the size of the BL images - will be reduced. - For example: moving MbedTLS function into the ROM library reduces BL1 and - BL2, but not BL31. + will be reduced. + For example: moving MbedTLS function into the ROM library reduces BL1 and + BL2, but not BL31. + - This change in BL images size can be taken into consideration to optimize the - memory layout when defining the BLx_BASE macros. + memory layout when defining the BLx_BASE macros. Build library at ROM ~~~~~~~~~~~~~~~~~~~~~ -The environment variable ``CROSS_COMPILE`` must be set as per the user guide. +The environment variable ``CROSS_COMPILE`` must be set appropriately. Refer to +:ref:`Performing an Initial Build` for more information about setting this +variable. + In the below example the usage of ROMLIB together with mbed TLS is demonstrated to showcase the benefits of library at ROM - it's not mandatory. |