The NXP i.MX8QXP CPU provides a set of one-time programmable bits (eFuses) organized in a fuse array. The fuse array is available in 1, 2, 4, 8 and 16K bits.

These bits can be blown just once. Programming them is an irreversible operation.

Kernel configuration

You can manage the OTP support through the following kernel configuration options:

  • NXP NVMEM On-Chip OTP Memory support (CONFIG_NVMEM_IMX_OCOTP)

  • NXP NVMEM SCU On-Chip OTP memory support (CONFIG_NVMEM_IMX_SCU_OCOTP)

These options are enabled as built-in on the default ConnectCore 8X kernel configuration file.

Kernel driver

The OTP drivers are located at:

File Description

drivers/nvmem/imx-ocotp.c

OTP driver for the i.MX8X

drivers/nvmem/imx-scu-ocotp.c

OTP driver for the i.MX8X SCU

Device tree bindings

The device tree node for the OTP driver is defined in the common i.MX8QXP device tree file:

i.MX8QXP device tree
ocotp: ocotp {
	#address-cells = <1>;
	#size-cells = <1>;
	compatible = "fsl,imx8qxp-ocotp", "syscon";
};

OTP user space usage

The OTP words are accessible (read-only) through the sysfs at /sys/devices/platform/ocotp/imx-ocotp0/nvmem.

~# od -A x -x /sys/devices/platform/ocotp/imx-ocotp0/nvmem
000000 0000 0000 0008 0000 000b 0000 0000 0000
000010 0002 0000 0000 0000 0000 0000 0000 0000
000020 0000 0000 0000 0000 0000 0000 0000 0000
000030 0000 0000 0000 0000 0003 0000 000c 0000
000040 bc4a 57ac 180b 0314 0000 0000 0000 0000
000050 0000 0000 0000 0000 0000 0000 0000 0000
*
000190 0000 2800 0000 0000 0022 2600 0000 0000
0001a0 0000 0000 0000 0000 0680 0000 0788 0000
0001b0 0000 0000 0000 0000 0000 0000 0000 0000
0001c0 1001 5500 0974 0000 4320 4603 0978 0000
0001d0 bf00 4629 0804 5500 2340 41fc 0000 8800
0001e0 0000 0000 0000 0000 0000 0000 0000 0000
*
0002e0 bada bada bada bada bada bada bada bada
*
000320 0000 0000 0000 0000 0000 0000 0000 0000
*
000400 0000 0000 2010 05c0 0000 0000 0000 0000
000410 0000 0000 0000 0000 0000 0000 0000 0000
*
000c40 5e33 8315 0000 0000 bada bada bada bada
000c50 0000 0000 0000 0000 0000 0000 0000 0000
*
0000c80