From mboxrd@z Thu Jan  1 00:00:00 1970
From: Kever Yang <kever.yang@rock-chips.com>
Date: Tue, 21 Nov 2017 17:38:13 +0800
Subject: [U-Boot] U-Boot proper(not SPL) relocate option
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To: u-boot@lists.denx.de

Hi Guys,

     I try to understand why we need to do the relocate in U-Boot.
 From the document README/crt0.S, I think the relocation feature comes
from some SoC have limited SRAM whose size is enough to load the whole
U-Boot, but not enough to run all the drivers.

     I don't know how many SoCs/Archs still must use this feature, but 
I'm sure all
Rockchip SoCs do not need this feature in both SPL and proper U-Boot,
because rockchip using SPL always running in SRAM to init DDR SDRAM,
and after DRAM available always running U-Boot in DRAM.

There is a CONFIG_SPL_SKIP_RELOCATE for SPL to skip the relocate,
can we have another CONFIG_SKIP_RELOCATE for U-Boot proper?

If we enable relocate in SPL, we init serial driver 4 times not 
including debug uart.
- before and after relocate in SPL, before and after U-Boot.


Here is the document from README:

board_init_f():
         - purpose: set up the machine ready for running board_init_r():
                 i.e. SDRAM and serial UART
         - global_data is available
         - stack is in SRAM
         - BSS is not available, so you cannot use global/static variables,
                 only stack variables and global_data

         Non-SPL-specific notes:
         - dram_init() is called to set up DRAM. If already done in SPL 
this
                 can do nothing

         SPL-specific notes:
         - you can override the entire board_init_f() function with your own
                 version as needed.
         - preloader_console_init() can be called here in extremis
         - should set up SDRAM, and anything needed to make the UART work
         - these is no need to clear BSS, it will be done by crt0.S
         - must return normally from this function (don't call 
board_init_r()
                 directly)

board_init_r():
         - purpose: main execution, common code
         - global_data is available
         - SDRAM is available
         - BSS is available, all static/global variables can be used
         - execution eventually continues to main_loop()

         Non-SPL-specific notes:
         - U-Boot is relocated to the top of memory and is now running from
                 there.

         SPL-specific notes:
         - stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is 
defined and
                 CONFIG_SPL_STACK_R_ADDR points into SDRAM
         - preloader_console_init() can be called here - typically this is
                 done by selecting CONFIG_SPL_BOARD_INIT and then 
supplying a
                 spl_board_init() function containing this call
         - loads U-Boot or (in falcon mode) Linux


Thanks,
- Kever