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kernel add
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/*
* DRAM/SDRAM initialization - alter with care
* This file is intended to be included from other assembler files
*
* Note: This file may not modify r9 because r9 is used to carry
* information from the decompresser to the kernel
*
* Copyright (C) 2000-2012 Axis Communications AB
*
*/
/* Just to be certain the config file is included, we include it here
* explicitly instead of depending on it being included in the file that
* uses this code.
*/
;; WARNING! The registers r8 and r9 are used as parameters carrying
;; information from the decompressor (if the kernel was compressed).
;; They should not be used in the code below.
move.d CONFIG_ETRAX_DEF_R_WAITSTATES, $r0
move.d $r0, [R_WAITSTATES]
move.d CONFIG_ETRAX_DEF_R_BUS_CONFIG, $r0
move.d $r0, [R_BUS_CONFIG]
#ifndef CONFIG_ETRAX_SDRAM
move.d CONFIG_ETRAX_DEF_R_DRAM_CONFIG, $r0
move.d $r0, [R_DRAM_CONFIG]
move.d CONFIG_ETRAX_DEF_R_DRAM_TIMING, $r0
move.d $r0, [R_DRAM_TIMING]
#else
;; Samsung SDRAMs seem to require to be initialized twice to work properly.
moveq 2, $r6
_sdram_init:
; Refer to ETRAX 100LX Designers Reference for a description of SDRAM initialization
; Bank configuration
move.d CONFIG_ETRAX_DEF_R_SDRAM_CONFIG, $r0
move.d $r0, [R_SDRAM_CONFIG]
; Calculate value of mrs_data
; CAS latency = 2 && bus_width = 32 => 0x40
; CAS latency = 3 && bus_width = 32 => 0x60
; CAS latency = 2 && bus_width = 16 => 0x20
; CAS latency = 3 && bus_width = 16 => 0x30
; Check if value is already supplied in kernel config
move.d CONFIG_ETRAX_DEF_R_SDRAM_TIMING, $r2
and.d 0x00ff0000, $r2
bne _set_timing
lsrq 16, $r2
move.d 0x40, $r2 ; Assume 32 bits and CAS latency = 2
move.d CONFIG_ETRAX_DEF_R_SDRAM_TIMING, $r1
move.d $r1, $r3
and.d 0x03, $r1 ; Get CAS latency
and.d 0x1000, $r3 ; 50 or 100 MHz?
beq _speed_50
nop
_speed_100:
cmp.d 0x00, $r1 ; CAS latency = 2?
beq _bw_check
nop
or.d 0x20, $r2 ; CAS latency = 3
ba _bw_check
nop
_speed_50:
cmp.d 0x01, $r1 ; CAS latency = 2?
beq _bw_check
nop
or.d 0x20, $r2 ; CAS latency = 3
_bw_check:
move.d CONFIG_ETRAX_DEF_R_SDRAM_CONFIG, $r1
and.d 0x800000, $r1 ; DRAM width is bit 23
bne _set_timing
nop
lsrq 1, $r2 ; 16 bits. Shift down value.
; Set timing parameters. Starts master clock
_set_timing:
move.d CONFIG_ETRAX_DEF_R_SDRAM_TIMING, $r1
and.d 0x8000f9ff, $r1 ; Make sure mrs data and command is 0
or.d 0x80000000, $r1 ; Make sure sdram enable bit is set
move.d $r1, $r5
or.d 0x0000c000, $r1 ; ref = disable
lslq 16, $r2 ; mrs data starts at bit 16
or.d $r2, $r1
move.d $r1, [R_SDRAM_TIMING]
; Wait 200us
move.d 10000, $r2
1: bne 1b
subq 1, $r2
; Issue initialization command sequence
move.d _sdram_commands_start, $r2
and.d 0x000fffff, $r2 ; Make sure commands are read from flash
move.d _sdram_commands_end, $r3
and.d 0x000fffff, $r3
1: clear.d $r4
move.b [$r2+], $r4
lslq 9, $r4 ; Command starts at bit 9
or.d $r1, $r4
move.d $r4, [R_SDRAM_TIMING]
nop ; Wait five nop cycles between each command
nop
nop
nop
nop
cmp.d $r2, $r3
bne 1b
nop
move.d $r5, [R_SDRAM_TIMING]
subq 1, $r6
bne _sdram_init
nop
ba _sdram_commands_end
nop
_sdram_commands_start:
.byte 3 ; Precharge
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 2 ; refresh
.byte 0 ; nop
.byte 1 ; mrs
.byte 0 ; nop
_sdram_commands_end:
#endif
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