diff options
| author | Bin Meng <bmeng.cn@gmail.com> | 2018-10-24 06:36:40 -0700 |
|---|---|---|
| committer | Simon Glass <sjg@chromium.org> | 2018-11-14 09:16:28 -0800 |
| commit | 1a6bd4717fe68ca212abca21a0e08af186fdb442 (patch) | |
| tree | 3d3d9d6ad45b88c9525fcf56772ed56728a12ddb /doc/driver-model | |
| parent | 8ee27da343aac7ba88b1efab620fc5ef30325ded (diff) | |
dm: doc: Update description of pre-relocation support
Add some description about pre-relocation driver binding, including
usage of DM_FLAG_PRE_RELOC flag and caveats.
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'doc/driver-model')
| -rw-r--r-- | doc/driver-model/README.txt | 16 |
1 files changed, 12 insertions, 4 deletions
diff --git a/doc/driver-model/README.txt b/doc/driver-model/README.txt index 36541630a2..07b120d512 100644 --- a/doc/driver-model/README.txt +++ b/doc/driver-model/README.txt @@ -830,10 +830,18 @@ Pre-Relocation Support ---------------------- For pre-relocation we simply call the driver model init function. Only -drivers marked with DM_FLAG_PRE_RELOC or the device tree -'u-boot,dm-pre-reloc' flag are initialised prior to relocation. This helps -to reduce the driver model overhead. This flag applies to SPL and TPL as -well, if device tree is enabled there. +drivers marked with DM_FLAG_PRE_RELOC or the device tree 'u-boot,dm-pre-reloc' +property are initialised prior to relocation. This helps to reduce the driver +model overhead. This flag applies to SPL and TPL as well, if device tree is +enabled (CONFIG_OF_CONTROL) there. + +Note when device tree is enabled, the device tree 'u-boot,dm-pre-reloc' +property can provide better control granularity on which device is bound +before relocation. While with DM_FLAG_PRE_RELOC flag of the driver all +devices with the same driver are bound, which requires allocation a large +amount of memory. When device tree is not used, DM_FLAG_PRE_RELOC is the +only way for statically declared devices via U_BOOT_DEVICE() to be bound +prior to relocation. It is possible to limit this to specific relocation steps, by using the more specialized 'u-boot,dm-spl' and 'u-boot,dm-tpl' flags |