RPIBOOT Mode

[cfernand2222]

In regards to provisioning a PI 4, the documentation states that a gpio pulled to ground is required to boot in 'rpiboot' mode.

The documentation also states that the 'rpi-sb-provisioner' can be configured to program one of the GPIOs in order to enter 'rpiboot' mode.

Since 'rpi-sb-provisioner' is connected to the raspi over usb and expects a usb device (rpiboot mode)', how does this work exactly ?

In other words, how does the provisioner program the gpio otp without the PI 4 being in rpiboot mode to begin with ?

[tdewey-rpi]

For Raspberry Pi 4 B form-factor devices, you must preprocess them to pre-assign the RPIBOOT GPIO. sb-provisioner lets you select that option on 2711 family devices regardless - because 2711 devices require that option to write the OTP customer signing key.

This is generally why I prefer to recommend compute modules or Raspberry Pi 5 family devices for mass deployment - the mass imaging story is much simpler for either group.

[timg236]

The tool to build an sd-card image which pre-assigns the RPIBOOT GPIO is here
https://github.com/raspberrypi/usbboot?tab=readme-ov-file#pi-4b-and-pi-400

[cfernand2222]

Since programming of a RPIBOOT GPIO is a prerequisite to provisioning a PI 4, what is the purpose of having an option to select a pin in the provisioning UI ?

sb-provisioner lets you select that option on 2711 family devices regardless - because 2711 devices require that option to write the OTP customer signing key.

From the response above, shouldn't it state that the 2711 requirement is that the device boots into rpiboot in order to write the OTP customer signing key ?

In other words, if PI 4s have to be preprocessed anyway, is there any use for the RPIBOOT_GPIO_PIN option in the provisioner ?

[tdewey-rpi]

Since programming of a RPIBOOT GPIO is a prerequisite to provisioning a PI 4, what is the purpose of having an option to select a pin in the provisioning UI ?

sb-provisioner lets you select that option on 2711 family devices regardless - because 2711 devices require that option to write the OTP customer signing key.

From the response above, shouldn't it state that the 2711 requirement is that the device boots into rpiboot in order to write the OTP customer signing key ?

In other words, if PI 4s have to be preprocessed anyway, is there any use for the RPIBOOT_GPIO_PIN option in the provisioner ?

For most users, no. In practice, if you somehow got your device into rpiboot mode without assigning that GPIO, however, this is a belt-and-braces approach to ensuring your signed boot keys are written.