If You have removable boot device (SD card, for example) - the simplest
way to enter i.MX6 serial boot mode is just removing the boot media (assuming boot
options are not changed, and are set, say, for SD boot ).
In such case, because of boot error, i.MX6 boot ROM enters serial boot mode automatically.
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In uboot we have any commands to change into serial download mode.
I think old version of uboot have download_mode command, by using this we can use MFG tool without boot switch. but latest uboot it's not there.
Any other commands are there to go to serial download mode option on uboot.
In case anyone is wondering how to enter serial downloader mode from U-Boot without altering the BOOT_MODE pin selections, I dug around and found that there are some undocumented registers that can do this. For me, the bmode usb command was not a valid U-Boot command as it's only support on some i.MX6 and i.MX6 platforms and I'm on a i.MX 8M Mini (imx8mm). Following the U-Boot code for how it works on an i.MX6 platform (which is very similar to i.MX8) I've found a working solution.
30390098: 00000000 ? 40000000
30390098: 40000000 ? .
The part will reset and enter serial downloader mode. Super useful.
Yes, it works for me on the imx8mm (i.MX 8M Mini). It does not work on a imx8mp (i.MX 8M Plus), and I suspect it would work on a imx8mn (i.MX 8M Nano).
The USB SDP only works on USB0. Unrelated to SDP, I have successfully used USB0 and USB1 as device gadgets in Linux. I have not tested host mode or otg.
thanks for the reply, unfortunately we have usb2 configured for device/otg/host modes, we use usb1 for something else.
i bumped across a spl kconfig "SPL_SDP_USB_DEV", wonder if i can change this to use usb2 instead.
int "SDP USB controller index"
depends on SPL_USB_SDP_SUPPORT
Some boards have USB controller other than 0. Define this option
so it can be used in compiled environment.
Sorry, I'm too used to counting from 0. The imx8mm has two USB OTG capable ports: USB OTG1 and USB OTG2.
SDP can only only be used with USB OTG1--that's a function of the boot capability of the part and documented in the boot chapter of the reference manual. There's nothing you can change in U-Boot to change this as it is intrinsic to the part. If there was a setting, it would have to be a fuse or something because SDP relates to how the part boots, prior to running any software you'd be able to configure.