Add a bit more information about how to use SPL.
Signed-off-by: Simon Glass sjg@chromium.org ---
(no changes since v1)
doc/develop/spl.rst | 34 ++++++++++++++++++++++++++++++++++ 1 file changed, 34 insertions(+)
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