1 /* $Id: dram_init.S,v 1.15 2003/09/22 09:22:22 starvik Exp $
3 * DRAM/SDRAM initialization - alter with care
4 * This file is intended to be included from other assembler files
6 * Note: This file may not modify r9 because r9 is used to carry
7 * information from the decompresser to the kernel
9 * Copyright (C) 2000, 2001 Axis Communications AB
11 * Authors: Mikael Starvik (starvik@axis.com)
13 * $Log: dram_init.S,v $
14 * Revision 1.15 2003/09/22 09:22:22 starvik
15 * Decompresser is linked to 0x407xxxxx and sdram commands are at 0x000xxxxx
16 * so we need to mask off 12 bits.
18 * Revision 1.14 2003/03/31 07:07:08 starvik
19 * Corrected calculation of end of sdram init commands
21 * Revision 1.13 2002/10/30 07:42:28 starvik
22 * Always read SDRAM command sequence from flash
24 * Revision 1.12 2002/08/09 11:37:37 orjanf
25 * Added double initialization work-around for Samsung SDRAMs.
27 * Revision 1.11 2002/06/04 11:43:21 starvik
28 * Check if mrs_data is specified in kernelconfig (necessary for MCM)
30 * Revision 1.10 2001/10/04 12:00:21 martinnn
31 * Added missing underscores.
33 * Revision 1.9 2001/10/01 14:47:35 bjornw
34 * Added register prefixes and removed underscores
36 * Revision 1.8 2001/05/15 07:12:45 hp
37 * Copy warning from head.S about r8 and r9
39 * Revision 1.7 2001/04/18 12:05:39 bjornw
40 * Fixed comments, and explicitely include config.h to be sure its there
42 * Revision 1.6 2001/04/10 06:20:16 starvik
43 * Delay should be 200us, not 200ns
45 * Revision 1.5 2001/04/09 06:01:13 starvik
46 * Added support for 100 MHz SDRAMs
48 * Revision 1.4 2001/03/26 14:24:01 bjornw
49 * Namechange of some config options
51 * Revision 1.3 2001/03/23 08:29:41 starvik
52 * Corrected calculation of mrs_data
54 * Revision 1.2 2001/02/08 15:20:00 starvik
55 * Corrected SDRAM initialization
56 * Should now be included as inline
58 * Revision 1.1 2001/01/29 13:08:02 starvik
60 * This file should be included from all assembler files that needs to
61 * initialize DRAM/SDRAM.
65 /* Just to be certain the config file is included, we include it here
66 * explicitely instead of depending on it being included in the file that
70 #include <linux/config.h>
72 ;; WARNING! The registers r8 and r9 are used as parameters carrying
73 ;; information from the decompressor (if the kernel was compressed).
74 ;; They should not be used in the code below.
76 #ifndef CONFIG_SVINTO_SIM
77 move.d CONFIG_ETRAX_DEF_R_WAITSTATES, $r0
78 move.d $r0, [R_WAITSTATES]
80 move.d CONFIG_ETRAX_DEF_R_BUS_CONFIG, $r0
81 move.d $r0, [R_BUS_CONFIG]
83 #ifndef CONFIG_ETRAX_SDRAM
84 move.d CONFIG_ETRAX_DEF_R_DRAM_CONFIG, $r0
85 move.d $r0, [R_DRAM_CONFIG]
87 move.d CONFIG_ETRAX_DEF_R_DRAM_TIMING, $r0
88 move.d $r0, [R_DRAM_TIMING]
90 ;; Samsung SDRAMs seem to require to be initialized twice to work properly.
94 ; Refer to ETRAX 100LX Designers Reference for a description of SDRAM initialization
97 move.d CONFIG_ETRAX_DEF_R_SDRAM_CONFIG, $r0
98 move.d $r0, [R_SDRAM_CONFIG]
100 ; Calculate value of mrs_data
101 ; CAS latency = 2 && bus_width = 32 => 0x40
102 ; CAS latency = 3 && bus_width = 32 => 0x60
103 ; CAS latency = 2 && bus_width = 16 => 0x20
104 ; CAS latency = 3 && bus_width = 16 => 0x30
106 ; Check if value is already supplied in kernel config
107 move.d CONFIG_ETRAX_DEF_R_SDRAM_TIMING, $r2
108 and.d 0x00ff0000, $r2
112 move.d 0x40, $r2 ; Assume 32 bits and CAS latency = 2
113 move.d CONFIG_ETRAX_DEF_R_SDRAM_TIMING, $r1
115 and.d 0x03, $r1 ; Get CAS latency
116 and.d 0x1000, $r3 ; 50 or 100 MHz?
120 cmp.d 0x00, $r1 ; CAS latency = 2?
123 or.d 0x20, $r2 ; CAS latency = 3
127 cmp.d 0x01, $r1 ; CAS latency = 2?
130 or.d 0x20, $r2 ; CAS latency = 3
132 move.d CONFIG_ETRAX_DEF_R_SDRAM_CONFIG, $r1
133 and.d 0x800000, $r1 ; DRAM width is bit 23
136 lsrq 1, $r2 ; 16 bits. Shift down value.
138 ; Set timing parameters. Starts master clock
140 move.d CONFIG_ETRAX_DEF_R_SDRAM_TIMING, $r1
141 and.d 0x8000f9ff, $r1 ; Make sure mrs data and command is 0
142 or.d 0x80000000, $r1 ; Make sure sdram enable bit is set
144 or.d 0x0000c000, $r1 ; ref = disable
145 lslq 16, $r2 ; mrs data starts at bit 16
147 move.d $r1, [R_SDRAM_TIMING]
154 ; Issue initialization command sequence
155 move.d _sdram_commands_start, $r2
156 and.d 0x000fffff, $r2 ; Make sure commands are read from flash
157 move.d _sdram_commands_end, $r3
158 and.d 0x000fffff, $r3
161 lslq 9, $r4 ; Command starts at bit 9
163 move.d $r4, [R_SDRAM_TIMING]
164 nop ; Wait five nop cycles between each command
172 move.d $r5, [R_SDRAM_TIMING]
176 ba _sdram_commands_end
179 _sdram_commands_start: