[PATCH v2 4/4] docs/system: arm: Add sabrelite board description

[Bin Meng <bmeng.cn@gmail.com>]

From: Bin Meng <bin.meng@windriver.com>

This adds the target guide for SABRE Lite board, and documents how
to boot a Linux kernel and U-Boot bootloader.

Signed-off-by: Bin Meng <bin.meng@windriver.com>

---

Changes in v2:
- new patch: add sabrelite target guide

 docs/system/arm/sabrelite.rst | 119 ++++++++++++++++++++++++++++++++++++++++++
 docs/system/target-arm.rst    |   1 +
 2 files changed, 120 insertions(+)
 create mode 100644 docs/system/arm/sabrelite.rst

diff --git a/docs/system/arm/sabrelite.rst b/docs/system/arm/sabrelite.rst
new file mode 100644
index 0000000..4c5d101
--- /dev/null
+++ b/docs/system/arm/sabrelite.rst
@@ -0,0 +1,119 @@
+Boundary Devices SABRE Lite (``sabrelite``)
+===========================================
+
+Boundary Devices SABRE Lite i.MX6 Development Board is a low-cost development
+platform featuring the powerful Freescale / NXP Semiconductor's i.MX 6 Quad
+Applications Processor.
+
+Supported devices
+-----------------
+
+The SABRE Lite machine supports the following devices:
+
+ * Up to 4 Cortex A9 cores
+ * Generic Interrupt Controller
+ * 1 Clock Controller Module
+ * 1 System Reset Controller
+ * 5 UARTs
+ * 2 EPIC timers
+ * 1 GPT timer
+ * 2 Watchdog timers
+ * 1 FEC ethernet controller
+ * 3 I2C controllers
+ * 7 GPIO controllers
+ * 4 SDHC storage controllers
+ * 4 USB 2.0 host controllers
+ * 5 ECSPI controllers
+ * 1 SST 25VF016B flash
+
+Please note above list is a complete superset the QEMU SABRE Lite machine can
+support. For a normal use case, a device tree blob that reprents a real world
+SABRE Lite board, only exposes a subset of devices to the guest software.
+
+Boot options
+------------
+
+The SABRE Lite machine can start using the standard -kernel functionality
+for loading a Linux kernel, U-Boot bootloader or ELF executable.
+
+Running Linux kernel
+--------------------
+
+Linux mainline v5.10 release is tested at the time of writing. To build a Linux
+mainline kernel that can be booted by the SABRE Lite machine, simply configure
+the kernel using the imx_v6_v7_defconfig configuration:
+
+.. code-block:: bash
+
+  $ export ARCH=arm
+  $ export CROSS_COMPILE=arm-linux-gnueabihf-
+  $ make imx_v6_v7_defconfig
+  $ make
+
+To boot the newly built Linux kernel in QEMU with the SABRE Lite machine, use:
+
+.. code-block:: bash
+
+  $ qemu-system-arm -M sabrelite -smp 4 -m 1G \
+      -display none -serial null -serial stdio \
+      -kernel arch/arm/boot/zImage \
+      -dtb arch/arm/boot/dts/imx6q-sabrelite.dtb \
+      -initrd /path/to/rootfs.ext4 \
+      -append "root=/dev/ram"
+
+Running U-Boot
+--------------
+
+U-Boot mainline v2020.10 release is tested at the time of writing. To build a
+U-Boot mainline bootloader that can be booted by the SABRE Lite machine, use
+the mx6qsabrelite_defconfig with similar commands as described above for Linux:
+
+.. code-block:: bash
+
+  $ export CROSS_COMPILE=arm-linux-gnueabihf-
+  $ make mx6qsabrelite_defconfig
+
+Note we need to adjust settings by:
+
+.. code-block:: bash
+
+  $ make menuconfig
+
+then manually select the following configuration in U-Boot:
+
+  Device Tree Control > Provider of DTB for DT Control > Embedded DTB
+
+To start U-Boot using the SABRE Lite machine, provide the u-boot binary to
+the -kernel argument, along with an SD card image with rootfs:
+
+.. code-block:: bash
+
+  $ qemu-system-arm -M sabrelite -smp 4 -m 1G \
+      -display none -serial null -serial stdio \
+      -kernel u-boot
+
+The following example shows booting Linux kernel from dhcp, and uses the
+rootfs on an SD card. This requies some additional command line parameters
+for QEMU:
+
+.. code-block:: none
+
+  -nic user,tftp=/path/to/kernel/zImage \
+  -drive file=sdcard.img,id=rootfs -device sd-card,drive=rootfs
+
+The directory for the built-in TFTP server should also contain the device tree
+blob of the SABRE Lite board. The sample SD card image was populated with the
+root file system with one single partition. You may adjust the kernel "root="
+boot parameter accordingly.
+
+After U-Boot boots, type the following commands in the U-Boot command shell to
+boot the Linux kernel:
+
+.. code-block:: none
+
+  => setenv ethaddr 00:11:22:33:44:55
+  => setenv bootfile zImage
+  => dhcp
+  => tftpboot 14000000 imx6q-sabrelite.dtb
+  => setenv bootargs root=/dev/mmcblk3p1
+  => bootz 12000000 - 14000000
diff --git a/docs/system/target-arm.rst b/docs/system/target-arm.rst
index bde4b8e..edd013c 100644
--- a/docs/system/target-arm.rst
+++ b/docs/system/target-arm.rst
@@ -83,6 +83,7 @@ undocumented; you can get a complete list by running
    arm/versatile
    arm/vexpress
    arm/aspeed
+   arm/sabrelite
    arm/digic
    arm/musicpal
    arm/gumstix
-- 
2.7.4