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diff --git a/docs/porting-guide.md b/docs/porting-guide.md index 91b2a2000..720c877f0 100644 --- a/docs/porting-guide.md +++ b/docs/porting-guide.md @@ -536,6 +536,34 @@ using the `platform_is_primary_cpu()` function. BL1 passed control to BL2 at if the platform wants to restrict the amount of memory visible to BL3-1. Details of this function are given below. +4. Loading the BL3-2 binary image (if present) in platform provided memory + using semi-hosting. To load the BL3-2 image, BL2 makes use of the + `bl32_meminfo` field in the `bl31_args` structure to which a pointer is + returned by the `bl2_get_bl31_args_ptr()` function. The platform also + defines the address in memory where BL3-2 is loaded through the constant + `BL32_BASE`. BL2 uses this information to determine if there is enough + memory to load the BL3-2 image. + +5. Arranging to pass control to the BL3-2 image (if present) that has been + pre-loaded at `BL32_BASE`. BL2 populates an `el_change_info` structure + in memory provided by the platform with information about how BL3-1 should + pass control to the BL3-2 image. This structure follows the + `el_change_info` structure populated for the normal world BL image in 2. + above. + +6. Populating a `meminfo` structure with the following information in + memory that is accessible by BL3-1 immediately upon entry. + + meminfo.total_base = Base address of memory visible to BL3-2 + meminfo.total_size = Size of memory visible to BL3-2 + meminfo.free_base = Base address of memory available for allocation + to BL3-2 + meminfo.free_size = Size of memory available for allocation to + BL3-2 + + BL2 populates this information in the `bl32_meminfo` field of the pointer + returned by the `bl2_get_bl31_args_ptr() function. + The following functions must be implemented by the platform port to enable BL2 to perform the above tasks. @@ -585,6 +613,11 @@ internal pointer (`bl2_to_bl31_args`) to a `bl31_args` which will be used by BL2 to pass information to BL3_1. The pointer is initialized to the base address of Secure DRAM (`0x06000000`). +The ARM FVP port also populates the `bl32_meminfo` field in the `bl31_args` +structure pointed to by `bl2_to_bl31_args` with the extents of memory available +for use by the BL3-2 image. The memory is allocated in the Secure DRAM from the +address defined by the constant `BL32_BASE`. + The non-secure memory extents used for loading BL3-3 are also initialized in this function. This information is accessible in the `bl33_meminfo` field in the `bl31_args` structure pointed to by `bl2_to_bl31_args`. |