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/* $Id: dram_init.S,v 1.4 2005/04/24 18:48:32 starvik Exp $
*
* DRAM/SDRAM initialization - alter with care
* This file is intended to be included from other assembler files
*
* Note: This file may not modify r8 or r9 because they are used to
* carry information from the decompresser to the kernel
*
* Copyright (C) 2000-2003 Axis Communications AB
*
* Authors: Mikael Starvik (starvik@axis.com)
*/
/* Just to be certain the config file is included, we include it here
* explicitely instead of depending on it being included in the file that
* uses this code.
*/
#include <asm/arch/hwregs/asm/reg_map_asm.h>
#include <asm/arch/hwregs/asm/bif_core_defs_asm.h>
;; 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.
; Refer to BIF MDS for a description of SDRAM initialization
; Bank configuration
move.d REG_ADDR(bif_core, regi_bif_core, rw_sdram_cfg_grp0), $r0
move.d CONFIG_ETRAX_SDRAM_GRP0_CONFIG, $r1
move.d $r1, [$r0]
move.d REG_ADDR(bif_core, regi_bif_core, rw_sdram_cfg_grp1), $r0
move.d CONFIG_ETRAX_SDRAM_GRP1_CONFIG, $r1
move.d $r1, [$r0]
; 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_SDRAM_COMMAND, $r2
bne _set_timing
nop
move.d 0x40, $r4 ; Assume 32 bits and CAS latency = 2
move.d CONFIG_ETRAX_SDRAM_TIMING, $r1
and.d 0x07, $r1 ; Get CAS latency
cmpq 2, $r1 ; CL = 2 ?
beq _bw_check
nop
move.d 0x60, $r4
_bw_check:
; Assume that group 0 width is equal to group 1. This assumption
; is wrong for a group 1 only hardware (such as the grand old
; StorPoint+).
move.d CONFIG_ETRAX_SDRAM_GRP0_CONFIG, $r1
and.d 0x200, $r1 ; DRAM width is bit 9
beq _set_timing
lslq 2, $r4 ; mrs_data starts at bit 2
lsrq 1, $r4 ; 16 bits. Shift down value.
; Set timing parameters (refresh off to avoid Guinness TR 83)
_set_timing:
move.d CONFIG_ETRAX_SDRAM_TIMING, $r1
and.d ~(3 << reg_bif_core_rw_sdram_timing___ref___lsb), $r1
move.d REG_ADDR(bif_core, regi_bif_core, rw_sdram_timing), $r0
move.d $r1, [$r0]
; Issue NOP command
move.d REG_ADDR(bif_core, regi_bif_core, rw_sdram_cmd), $r5
moveq regk_bif_core_nop, $r1
move.d $r1, [$r5]
; 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 $r6
move.b [$r2+], $r6 ; Load command
or.d $r4, $r6 ; Add calculated mrs
move.d $r6, [$r5] ; Write rw_sdram_cmd
; Wait 80 ns between each command
move.d 4000, $r7
2: bne 2b
subq 1, $r7
cmp.d $r2, $r3 ; Last command?
bne 1b
nop
; Start refresh
move.d CONFIG_ETRAX_SDRAM_TIMING, $r1
move.d REG_ADDR(bif_core, regi_bif_core, rw_sdram_timing), $r0
move.d $r1, [$r0]
; Initialization finished
ba _sdram_commands_end
nop
_sdram_commands_start:
.byte regk_bif_core_pre ; Precharge
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_ref ; refresh
.byte regk_bif_core_mrs ; mrs
_sdram_commands_end:
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