diff options
Diffstat (limited to 'kernel/arch/cris/arch-v10/lib/dram_init.S')
| -rw-r--r-- | kernel/arch/cris/arch-v10/lib/dram_init.S | 146 |
1 files changed, 146 insertions, 0 deletions
diff --git a/kernel/arch/cris/arch-v10/lib/dram_init.S b/kernel/arch/cris/arch-v10/lib/dram_init.S new file mode 100644 index 000000000..e541d3d8f --- /dev/null +++ b/kernel/arch/cris/arch-v10/lib/dram_init.S @@ -0,0 +1,146 @@ +/* + * 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 |