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Diffstat (limited to 'doc/README.fdt-control')
| -rw-r--r-- | doc/README.fdt-control | 18 |
1 files changed, 18 insertions, 0 deletions
diff --git a/doc/README.fdt-control b/doc/README.fdt-control index d6ab7bf570..446401c9e9 100644 --- a/doc/README.fdt-control +++ b/doc/README.fdt-control @@ -184,6 +184,24 @@ The full device tree is available to U-Boot proper, but normally only a subset 'SPL Support' in doc/driver-model/README.txt for more details. +Using several DTBs in the SPL (CONFIG_SPL_MULTI_DTB) +---------------------------------------------------- +In some rare cases it is desirable to let SPL be able to select one DTB among +many. This usually not very useful as the DTB for the SPL is small and usually +fits several platforms. However the DTB sometimes include information that do +work on several platforms (like IO tuning parameters). +In this case it is possible to use CONFIG_SPL_MULTI_DTB. This option appends to +the SPL a FIT image containing several DTBs listed in SPL_OF_LIST. +board_fit_config_name_match() is called to select the right DTB. + +If board_fit_config_name_match() relies on DM (DM driver to access an EEPROM +containing the board ID for example), it possible to start with a generic DTB +and then switch over to the right DTB after the detection. For this purpose, +the platform code must call fdtdec_resetup(). Based on the returned flag, the +platform may have to re-initiliaze the DM subusystem using dm_uninit() and +dm_init_and_scan(). + + Limitations ----------- |