docs(allwinner): add SUNXI_SETUP_REGULATORS build option
Document the newly introduced SUNXI_SETUP_REGULATORS build option, that
allows to disable PMIC regulator setup at build time.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Change-Id: Ie5fb0b7220426b67cfffc95df4cabb31a6ec174a
diff --git a/docs/plat/allwinner.rst b/docs/plat/allwinner.rst
index b696989..1bf4f51 100644
--- a/docs/plat/allwinner.rst
+++ b/docs/plat/allwinner.rst
@@ -26,6 +26,22 @@
make CROSS_COMPILE=aarch64-linux-gnu- PLAT=sun50i_h616 DEBUG=1 bl31
+Platform-specific build options
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The default build options should generate a working firmware image. There are
+some build options that allow to fine-tune the firmware, or to disable support
+for optional features.
+
+- ``SUNXI_SETUP_REGULATORS`` : On SoCs that typically ship with a PMIC
+ power management controller, BL31 tries to set up all needed power rails,
+ programming them to their respective voltages. That allows bootloader
+ software like U-Boot to ignore power control via the PMIC.
+ This setting defaults to 1. In some situations that enables too many
+ regulators, or some regulators need to be enabled in a very specific
+ sequence. To avoid problems with those boards, ``SUNXI_SETUP_REGULATORS``
+ can bet set to ``0`` on the build command line, to skip the PMIC setup
+ entirely. Any bootloader or OS would need to setup the PMIC on its own then.
Installation
------------