Due to limitations in debian wheezys userspace, the use of an initramfs. U-Boot would have to initialize the SoC's host USB controller, and perform the host/master side of the protocol. WARNING, this is now deprecated, please use U-Boot overlays. A USB device is responsible for its own initialization. BTW U-Boot would not " initialize the internal USB memory device". I have no idea if the 128KB is sufficient memory to execute a 2nd-stage boot program that could access a USB storage device. While youre doing this, press and release the power button. By modifying U-Boot source code, you can create your own built-in commands. Press and hold the volume-down button on the Surface. U-Boot commands 4.1 Overview U-Boot has a set of built-in commands for booting the system, managing memory, and updating an embedded system’s firmware. Using the standard SAMA5D4 boot ROM, per the SoC datasheet, the system is constrained to read from only the supported media for loading the next stage program of the boot sequence into the SRAM. Insert the bootable USB drive into the USB port on your Surface.
U boot list devices code#
Although this still requires an external NVM chip, this custom 1st-stage boot code could access any boot medium you choose and load theoretically anything including a Linux kernel. NOR flash) that contains a custom (first-stage) boot program. Some Atmel/Microchip SoCs have the capability to disable the ROM and instead (post-reset) start execution from an external NVM (e.g.
U boot list devices driver#
ifdef out all of the code in your driver except for the above. Is the only solution when wishing to employ these device with U-Boot/ Linux to use some other NVM source to boot U-Boot, & then get U-Boot to initialize the internal USB memory device & run from that? Not sure what you mean by " these device " you overuse the word "device(s)" when there are better word choices. Replace ‘exynos’ in the above code with your driver name. USB0: USB EHCI 1.00 scanning bus 0 for devices. Hence "booting directly" is ambiguous are you using an end-user or developer perspective? Leo738. I am able to see usb enabled at u-boot with the following prompt. Leo738 However it appears that devices such as the SAMA5D4 do not support booting directly from USB devices (see attached diagram taken from chip datasheet).Many ARM SoCs employ a multi-stage boot sequence with integrated SRAM (mostly to provide flexibility in implementing external DRAM for main memory). But to insert USB into the connection path of a device or interface that is already supported by the SoC seems to be useful in only special cases. In the past I did suggest using USB to someone that wanted to connect a SATA drive, since that was the simplest approach. Leo738 Embedded/ internal USB memory devices (example device) are an attractive storage/non-volatile memory (NVM) solution for embedded devices due to size, read/write cycles, power consumption etc.I wouldn't agree on those "advantages".
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