dm: mmc: Allow sandbox emulator to build without writes

[platform/kernel/u-boot.git] / board / sunxi / README.sunxi64

diff --git a/board/sunxi/README.sunxi64 b/board/sunxi/README.sunxi64
index 258921a..4803bc9 100644 (file)
--- a/board/sunxi/README.sunxi64
+++ b/board/sunxi/README.sunxi64
@@ -14,8 +14,12 @@ Quick Start / Overview
 - Build the ARM Trusted Firmware binary (see "ARM Trusted Firmware (ATF)" below)
   $ cd /src/arm-trusted-firmware
   $ make PLAT=sun50i_a64 DEBUG=1 bl31
+- Build the SCP firmware binary (see "SCP firmware (Crust)" below)
+  $ cd /src/crust
+  $ make pine64_plus_defconfig && make -j5 scp
 - Build U-Boot (see "SPL/U-Boot" below)
   $ export BL31=/path/to/bl31.bin
+  $ export SCP=/src/crust/build/scp/scp.bin
   $ make pine64_plus_defconfig && make -j5
 - Transfer to an uSD card (see "microSD card" below)
   $ dd if=u-boot-sunxi-with-spl.bin of=/dev/sdx bs=8k seek=1
@@ -24,13 +28,17 @@ Quick Start / Overview
 Building the firmware
 =====================
 
-The Allwinner A64/H5 firmware consists of three parts: U-Boot's SPL, an
-ARM Trusted Firmware (ATF) build and the U-Boot proper.
-The SPL will load both ATF and U-Boot proper along with the right device
-tree blob (.dtb) and will pass execution to ATF (in EL3), which in turn will
-drop into the U-Boot proper (in EL2).
-As the ATF binary will become part of the U-Boot image file, you will need
-to build it first.
+The Allwinner A64/H5/H6 firmware consists of several parts: U-Boot's SPL,
+ARM Trusted Firmware (ATF), optional System Control Processor (SCP) firmware
+(e.g. Crust), and the U-Boot proper.
+
+The SPL will load all of the other firmware binaries into RAM, along with the
+right device tree blob (.dtb), and will pass execution to ATF (in EL3). If SCP
+firmware was loaded, ATF will power on the SCP and wait for it to boot.
+ATF will then drop into U-Boot proper (in EL2).
+
+As the ATF binary and SCP firmware will become part of the U-Boot image file,
+you will need to build them first.
 
  ARM Trusted Firmware (ATF)
 ----------------------------
@@ -53,6 +61,31 @@ As sometimes the ATF build process is a bit picky about the toolchain used,
 or if you can't be bothered with building ATF, there are known working
 binaries in the firmware repository[3], purely for convenience reasons.
 
+ SCP firmware (Crust)
+----------------------
+SCP firmware is responsible for implementing system suspend/resume, and (on
+boards without a PMIC) soft poweroff/on. ATF contains fallback code for CPU
+power control, so SCP firmware is optional if you don't need either of these
+features. It runs on the AR100, with is an or1k CPU, not ARM, so it needs a
+different cross toolchain.
+
+There is one SCP firmware implementation currently available, Crust:
+$ git clone https://github.com/crust-firmware/crust
+$ cd crust
+$ export CROSS_COMPILE=or1k-linux-musl-
+$ make pine64_plus_defconfig
+$ make scp
+
+The same configuration generally works on any board with the same SoC (A64, H5,
+or H6), so if there is no config for your board, use one for a similar board.
+
+Like for ATF, U-Boot finds the SCP firmware binary via an environment variable:
+$ export SCP=/src/crust/build/scp/scp.bin
+
+If you do not want to use SCP firmware, you can silence the warning from binman
+by pointing it to an empty file:
+$ export SCP=/dev/null
+
  SPL/U-Boot
 ------------
 Both U-Boot proper and the SPL are using the 64-bit mode. As the boot ROM