diff options
| author | Simon Glass <sjg@chromium.org> | 2022-04-30 09:56:46 +0300 |
|---|---|---|
| committer | Tom Rini <trini@konsulko.com> | 2022-05-02 16:58:13 +0300 |
| commit | a36d251b509d9ed64ec0fc0f0dafc5dc0748e734 (patch) | |
| tree | 223f6e49bd55e0aa88d2ca62773c15fbe680d226 /doc | |
| parent | d411359d919a7efae5e9379b83986c553bc57b34 (diff) | |
| download | u-boot-a36d251b509d9ed64ec0fc0f0dafc5dc0748e734.tar.xz | |
doc: Expand SPL docs to explain the phase and config
Add a bit more information about how to use SPL.
Signed-off-by: Simon Glass <sjg@chromium.org>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/develop/spl.rst | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/doc/develop/spl.rst b/doc/develop/spl.rst index 4d6f394bed..1059b2fb9c 100644 --- a/doc/develop/spl.rst +++ b/doc/develop/spl.rst @@ -66,6 +66,40 @@ CONFIG_SPL_SPI_LOAD (drivers/mtd/spi/spi_spl_load.o) CONFIG_SPL_RAM_DEVICE (common/spl/spl.c) CONFIG_SPL_WATCHDOG (drivers/watchdog/libwatchdog.o) +Adding SPL-specific code +------------------------ + +To check whether a feature is enabled, use CONFIG_IS_ENABLED():: + + if (CONFIG_IS_ENABLED(CLK)) + ... + +This checks CONFIG_CLK for the main build, CONFIG_SPL_CLK for the SPL build, +CONFIG_TPL_CLK for the TPL build, etc. + +U-Boot Phases +------------- + +U-Boot boots through the following phases: + +TPL + Very early init, as tiny as possible. This loads SPL. + +SPL + Secondary program loader. Sets up SDRAM and loads U-Boot proper. It may also + load other firmware components. + +U-Boot + U-Boot proper, containing the command line and boot logic. + + +Checking the boot phase +----------------------- + +Use `spl_phase()` to find the current U-Boot phase, e.g. `PHASE_SPL`. You can +also find the previous and next phase and get the phase name. + + Device tree ----------- The U-Boot device tree is filtered by the fdtgrep tools during the build |