[PATCH v7 02/15] doc: Expand SPL docs to explain the phase and config

Simon Glass sjg at chromium.org
Mon Feb 28 15:16:44 CET 2022

Add a bit more information about how to use SPL.

Signed-off-by: Simon Glass <sjg at 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()::
+      ...
+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:
+   Very early init, as tiny as possible. This loads SPL.
+   Secondary program loader. Sets up SDRAM and loads U-Boot proper. It may also
+   load other firmware components.
+   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

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