mirror of
https://github.com/AsahiLinux/u-boot
synced 2024-12-22 11:13:07 +00:00
56 lines
1.7 KiB
Text
56 lines
1.7 KiB
Text
|
/*
|
||
|
|
* Copyright (C) 2016, Imagination Technologies Ltd.
|
||
|
|
*
|
||
|
|
* Zubair Lutfullah Kakakhel, Zubair.Kakakhel@imgtec.com
|
||
|
|
*/
|
||
|
|
|
||
|
|
MIPSfpga
|
||
|
|
=======================================
|
||
|
|
|
||
|
|
MIPSfpga is an FPGA based development platform by Imagination Technologies
|
||
|
|
As we are dealing with a MIPS core instantiated on an FPGA, specifications
|
||
|
|
are fluid and can be varied in RTL.
|
||
|
|
|
||
|
|
The example project provided by IMGTEC runs on the Nexys4DDR board by
|
||
|
|
Digilent powered by the ARTIX-7 FPGA by Xilinx. Relevant details about
|
||
|
|
the example project and the Nexys4DDR board:
|
||
|
|
|
||
|
|
- microAptiv UP core m14Kc
|
||
|
|
- 50MHz clock speed
|
||
|
|
- 128Mbyte DDR RAM at 0x0000_0000
|
||
|
|
- 8Kbyte RAM at 0x1000_0000
|
||
|
|
- axi_intc at 0x1020_0000
|
||
|
|
- axi_uart16550 at 0x1040_0000
|
||
|
|
- axi_gpio at 0x1060_0000
|
||
|
|
- axi_i2c at 0x10A0_0000
|
||
|
|
- custom_gpio at 0x10C0_0000
|
||
|
|
- axi_ethernetlite at 0x10E0_0000
|
||
|
|
- 8Kbyte BootRAM at 0x1FC0_0000
|
||
|
|
- 16Mbyte QPI at 0x1D00_0000
|
||
|
|
|
||
|
|
Boot protocol:
|
||
|
|
--------------
|
||
|
|
|
||
|
|
The BootRAM is a writeable "RAM" in FPGA at 0x1FC0_0000.
|
||
|
|
This is for easy reprogrammibility via JTAG.
|
||
|
|
|
||
|
|
DDR initialization is already handled by a HW IP block.
|
||
|
|
|
||
|
|
When the example project bitstream is loaded, the cpu_reset button
|
||
|
|
needs to be pressed.
|
||
|
|
|
||
|
|
The bootram initializes the cache and axi_uart
|
||
|
|
Then checks if there is anything non 0xffff_ffff at location 0x1D40_0000
|
||
|
|
|
||
|
|
If there is, then that is considered as u-boot. u-boot is copied from
|
||
|
|
0x1D40_0000 to memory and the bootram jumps into u-boot code.
|
||
|
|
|
||
|
|
At this point, the board is ready to load the Linux kernel + buildroot initramfs
|
||
|
|
|
||
|
|
This can be done in multiple ways:
|
||
|
|
|
||
|
|
1- JTAG load the binary and jump into it.
|
||
|
|
2- Load kernel stored in the QSPI flash at 0x1D80_0000
|
||
|
|
3- Load uImage via tftp. Ethernet works in u-boot.
|
||
|
|
e.g. env set server ip 192.168.154.45; dhcp uImage; bootm
|