转：blob how to start the xscale pxa27x

November 10

blob, how to start

blob how to start the xscale pxa27x

step 1

.../src/blob/start.S  _start: b reset -->

.../src/blob/xlli/mainstone/start.s  

 (1) reset: check why reset

 (2) if (reset = GPIO or power_on or watchdog reset) do following (3) 

     if (reset = sleep reset) jump to (4)

 (3) Reads the SCR and LCDR virtural registers and places in SRAM

 (4) init GPIO

 (5) init clocks (basic clock, just for boot)

 (6) init power manager and internal memory

 (7) init Memory Controller

 (8) init Interrupt

 (9) init clocks (only when sleep reset)

 (10) change the CPU and RAM clocks, proform in high frequence

 (11) init OS timer

 (12) if power or battary error (only when sleep reset)

 finish basic init, b normal_boot -->

step 2

.../src/blob/start.S normal_boot: 

 (1) check the first 1MB of SDRAM, it will store the BLOB_START

 (2) copy form "piggy_start" to SDRAM

     __piggy_start = blob-rest-piggy.o

 (3) jump to "BLOB_START" (address: 0xa0300400)

note : previous program run in FLASH (CPU read cmd and data direct form FLASH)

 following program will run in SDRAM

  

  -- >

step 3

.../src/blob/trampoline.S 

 (1) clear SDRAM (just some section, not all)

 (2) setup the stack

 (3) jump to main

note : previous program are assembly

 following program are C

 -->

step 4

.../src/blob/main.c

 (1) init_subsystems() 

 <1> init flash driever (init_mainstone_flash_driver()) 

 <2> init hardware (set IP address, mainstone_init_hardware())

 <3> init serial (serial_default_init())

 <4> init icache

 <5> init led

 <6> init net (ether_init()) !!!!

 <8> init command

 <9> init flash blocks table (in flash.c)

 <10> find partiton table (in partition.c: ptable_init())

 (2) reload blob, kernel, filesystem.

 (3) print some welcome info, wait user input, or timeout, start kernel