Hi Stefan,
From: Stefan Agner stefan.agner@toradex.com
Document the U-Boot Serial Download Protocol implementation and some typical use cases.
Thanks for providing the description :-)
Reviewed-by: Łukasz Majewski lukma@denx.de
Signed-off-by: Stefan Agner stefan.agner@toradex.com
This ended up to be almost more a imx_usb documentation. But there is really not much to document from a U-Boot side since actual usage heavily depends on host side tooling...
This assumes that the necessary changes will get merged upstream: https://github.com/toradex/imx_loader/tree/imx_usb_batch_mode_refactored
Changes in v2: None
doc/README.sdp | 100 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 100 insertions(+) create mode 100644 doc/README.sdp
diff --git a/doc/README.sdp b/doc/README.sdp new file mode 100644 index 0000000000..9b438c0746 --- /dev/null +++ b/doc/README.sdp @@ -0,0 +1,100 @@ +------------- +SDP in U-Boot +-------------
+SDP stands for serial download protocol. It is the protocol used in NXP's +i.MX SoCs ROM Serial Downloader and provides means to download a program +image to the chip over USB and UART serial connection.
+The implementation in U-Boot uses the USB Downloader Gadget (g_dnl) to +provide a SDP implementation over USB. This allows to download program +images to the target in SPL/U-Boot using the same protocol/tooling the +SoC's recovery mechanism is using.
+The SDP protocol over USB is a USB HID class protocol. USB HID class +protocols allow to access a USB device without OS specific drivers. The +U-Boot implementation has primarly been tested using the open source +imx_loader utility (https://github.com/toradex/imx_loader).
+The host side utilities are typically capable to interpret the i.MX +specific image header (see doc/README.imximage). There are extensions +for imx_loader's imx_usb utility which allow to interpret the U-Boot +specific legacy image format (see mkimage(1)). Also the U-Boot side +support beside the i.MX specific header the U-Boot legacy header.
+Usage +-----
+This implementation can be started in U-Boot using the sdp command +(CONFIG_CMD_USB_SDP) or in SPL if Serial Downloader boot mode has been +detected (CONFIG_SPL_USB_SDP_SUPPORT).
+A typical use case is downloading full U-Boot after SPL has been +downloaded through the boot ROM's Serial Downloader. Using boot mode +detection the SPL will run the SDP implementation automatically in +this case:
- # imx_usb SPL
+Targets Serial Console:
- Trying to boot from USB SDP
- SDP: initialize...
- SDP: handle requests...
+At this point the SPL reenumerated as a new HID device and emulating +the boot ROM's SDP protocol. The USB VID/PID will depend on standard +U-Boot configurations CONFIG_G_DNL_(VENDOR|PRODUCT)_NUM. Make sure +imx_usb is aware of the USB VID/PID for your device by adding a +configuration entry in imx_usb.conf:
- 0x1b67:0x4fff, mx6_usb_sdp_spl.conf
+And the device specific configuration file mx6_usb_sdp_spl.conf:
- mx6_spl_sdp
- hid,uboot_header,1024,0x910000,0x10000000,1G,0x00900000,0x40000
+This allows to download the regular U-Boot with legacy image headers +(u-boot.img) using a second invocation of imx_usb:
- # imx_usb u-boot.img
+Furthermore, when U-Boot is running the sdp command can be used to +download and run scripts:
- # imx_usb script.scr
+imx_usb configuration files can be also used to download multiple +files and of arbitrary types, e.g.
- mx6_usb_sdp_uboot
- hid,1024,0x10000000,1G,0x00907000,0x31000
- full.itb:load 0x12100000
- boot.scr:load 0x12000000,jump 0x12000000
+There is also a batch mode which allows imx_usb to handle multiple +consecutive reenumerations by adding multiple VID/PID specifications +in imx_usb.conf:
- 0x15a2:0x0061, mx6_usb_rom.conf, 0x1b67:0x4fff, mx6_usb_sdp_spl.conf
+In this mode the file to download (imx_usb job) needs to be specified +in the configuration files.
+mx6_usb_rom.conf:
- mx6_qsb
- hid,1024,0x910000,0x10000000,1G,0x00900000,0x40000
- SPL:jump header2
+mx6_usb_sdp_spl.conf:
- mx6_spl_sdp
- hid,uboot_header,1024,0x10000000,1G,0x00907000,0x31000
- u-boot.img:jump header2
+With that SPL and U-Boot can be downloaded with a single invocation +of imx_usb without arguments:
- # imx_usb