pico-imx7d: Add instructions for booting in Falcon mode

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@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>

diff --git a/board/technexion/pico-imx7d/README b/board/technexion/pico-imx7d/README
index 6aa0d25..4d57cdb 100644 (file)
--- 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@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
+...