[U-Boot] [PATCH 4/5] pico-imx7d: Add instructions for booting in Falcon mode

[Otavio Salvador]

From: Fabio Estevam <festevam at gmail.com>

Improve the README by adding instructions on how to boot using
Falcon mode, which allows the SPL to load the kernel directly,
without using U-Boot proper.

Signed-off-by: Fabio Estevam <festevam at gmail.com>
Signed-off-by: Otavio Salvador <otavio at ossystems.com.br>
---

 board/technexion/pico-imx7d/README | 91 ++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)

diff --git a/board/technexion/pico-imx7d/README b/board/technexion/pico-imx7d/README
index 6aa0d25af5..4d57cdbfa8 100644
--- a/board/technexion/pico-imx7d/README
+++ b/board/technexion/pico-imx7d/README
@@ -66,3 +66,94 @@ Remove power from the pico board.
 Put pico board into normal boot mode.
 
 Power up the board and the new updated U-Boot should boot from eMMC.
+
+Booting in Falcon mode
+======================
+
+Generate a uImage kernel:
+
+$ make imx_v6_v7_defconfig (Using the default imx_v6_v7_defconfig configuration
+just for an example. In order to boot faster the user should customize the
+defconfig by only enabling the minimal required drivers).
+
+$ make -j4 uImage LOADADDR=0x80008000
+
+$ cp arch/arm/boot/uImage /tftpboot
+$ cp arch/arm/boot/dts/imx7d-pico-pi.dtb /tftpboot
+
+In the U-Boot prompt:
+
+Setup the server and board IP addresses:
+=> setenv serverip 192.168.0.10
+=> setenv ipaddr 192.168.0.11
+
+Get the dtb file:
+=> tftp ${fdt_addr} imx7d-pico-pi.dtb
+
+Get the kernel:
+=> tftp ${loadaddr} uImage
+
+Write the kernel at 2MB offset:
+=> mmc write ${loadaddr} 0x1000 0x5000
+
+Setup the bootargs:
+=> setenv bootargs 'console=ttymxc4,115200 root=/dev/mmcblk2p1 rootfstype=ext4 rootwait rw'
+
+Prepare args:
+=> spl export fdt ${loadaddr} - ${fdt_addr}
+## Booting kernel from Legacy Image at 80800000 ...
+   Image Name:   Linux-5.2.14
+   Image Type:   ARM Linux Kernel Image (uncompressed)
+   Data Size:    9077544 Bytes = 8.7 MiB
+   Load Address: 80008000
+   Entry Point:  80008000
+   Verifying Checksum ... OK
+## Flattened Device Tree blob at 83000000
+   Booting using the fdt blob at 0x83000000
+   Loading Kernel Image
+   Using Device Tree in place at 83000000, end 8300b615
+subcommand not supported
+subcommand not supported
+   Using Device Tree in place at 83000000, end 8300e615
+Argument image is now in RAM: 0x83000000
+=>
+
+Write 1MB of args data (0x800 sectors) to 1MB offset (0x800 sectors):
+
+=> mmc write ${fdt_addr} 0x800 0x800
+
+In order to boot with Falcon mode, activate the CONFIG_SPL_OS_BOOT
+option in the defconfig
+
+--- a/configs/pico-imx7d_defconfig
++++ b/configs/pico-imx7d_defconfig
+@@ -67,3 +67,4 @@ CONFIG_USB_GADGET_VENDOR_NUM=0x0525
+ CONFIG_USB_GADGET_PRODUCT_NUM=0xa4a5
+ CONFIG_CI_UDC=y
+ CONFIG_VIDEO=y
++CONFIG_SPL_OS_BOOT=y
+
+Then rebuild U-Boot:
+
+$ make pico-imx7d_defconfig
+$ make -j4
+
+Launch UMS:
+=> ums 0 mmc 0
+
+Flash the new binaries:
+
+$ sudo dd if=SPL of=/dev/sdX bs=1k seek=1; sync
+$ sudo dd if=u-boot-dtb.img  of=/dev/sdX bs=1k seek=69; sync
+
+And then SPL binary will load and jump directly to the kernel:
+
+U-Boot SPL 2019.10-rc3-00284-g001c8ea94a-dirty (Sep 10 2019 - 12:46:01 -0300)
+Trying to boot from MMC1
+[    0.000000] Booting Linux on physical CPU 0x0
+[    0.000000] Linux version 5.2.14 (fabio at fabio-OptiPlex-7010) (gcc version 7.4.0 (Ubuntu/Linaro 7.4.0-1ubuntu1~18.04.1)) #30 SMP Wed Sep 10 12:36:27 -03 2019
+[    0.000000] CPU: ARMv7 Processor [410fc075] revision 5 (ARMv7), cr=10c5387d
+[    0.000000] CPU: div instructions available: patching division code
+[    0.000000] CPU: PIPT / VIPT nonaliasing data cache, VIPT aliasing instruction cache
+[    0.000000] OF: fdt: Machine model: TechNexion PICO-IMX7D Board and PI baseboard
+...
-- 
2.23.0