1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
#include <machine/asm.h>
#include <arm/at91/at91_rstreg.h>
#include <arm/at91/at91reg.h>
#include <arm/at91/at91sam9g20reg.h>
__FBSDID("$FreeBSD$");
#define SDRAM_TR (AT91_BASE + \
AT91SAM9G20_SDRAMC_BASE + AT91SAM9G20_SDRAMC_TR)
#define SDRAM_LPR (AT91_BASE + \
AT91SAM9G20_SDRAMC_BASE + AT91SAM9G20_SDRAMC_LPR)
#define RSTC_RCR (AT91_BASE + \
AT91SAM9G20_RSTC_BASE + RST_CR)
/*
* From AT91SAM9G20 Datasheet errata 44:3.5:
*
* When User Reset occurs durring SDRAM read acces, eh SDRAM clock is turned
* off while data are ready to be read on the data bus. The SDRAM maintains
* the data until the clock restarts.
*
* If the User reset is programed to assert a general reset, the data
* maintained by the SDRAM leads to a data bus conflict and adversly affects
* the boot memories connected to the EBI:
* + NAND Flash boot functionality, if the system boots out of internal ROM.
* + NOR Flash boot, if the system boots on an external memory connected to
* the EBI CS0.
*
* Assembly code is mandatory for the following sequnce as ARM
* instructions need to be piplined.
*
*/
ENTRY(cpu_reset_sam9g20)
/* Disable IRQs */
mrs r0, cpsr
orr r0, r0, #0x80
msr cpsr_c, r0
/* Change Refresh to block all data access */
ldr r0, =SDRAM_TR
ldr r1, =1
str r1, [r0]
/* Prepare power down command */
ldr r0, =SDRAM_LPR
ldr r1, =2
/* Prepare proc_reset and periph reset */
ldr r2, =RSTC_RCR
ldr r3, =0xA5000005
/* perform power down command */
str r1, [r0]
/* Perfom proc_reset and periph reset (in the ARM pipeline) */
str r3, [r2]
|
