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+##=============================================================================
+##
+## nand_init.S
+##
+## The bootrom copies data from the NAND flash to the internal RAM but
+## due to a bug/feature we can only trust the 256 first bytes. So this
+## code copies more data from NAND flash to internal RAM. Obvioulsy this
+## code must fit in the first 256 bytes so alter with care.
+##
+## Some notes about the bug/feature for future reference:
+## The bootrom copies the first 127 KB from NAND flash to internal
+## memory. The problem is that it does a bytewise copy. NAND flashes
+## does autoincrement on the address so for a 16-bite device each
+## read/write increases the address by two. So the copy loop in the
+## bootrom will discard every second byte. This is solved by inserting
+## zeroes in every second byte in the first erase block.
+##
+## The bootrom also incorrectly assumes that it can read the flash
+## linear with only one read command but the flash will actually
+## switch between normal area and spare area if you do that so we
+## can't trust more than the first 256 bytes.
+##
+##=============================================================================
+
+#include <asm/arch/hwregs/asm/reg_map_asm.h>
+#include <asm/arch/hwregs/asm/gio_defs_asm.h>
+#include <asm/arch/hwregs/asm/pinmux_defs_asm.h>
+#include <asm/arch/hwregs/asm/bif_core_defs_asm.h>
+#include <asm/arch/hwregs/asm/config_defs_asm.h>
+#include <linux/config.h>
+
+;; There are 8-bit NAND flashes and 16-bit NAND flashes.
+;; We need to treat them slightly different.
+#if CONFIG_ETRAX_FLASH_BUSWIDTH==2
+#define PAGE_SIZE 256
+#else
+#error 2
+#define PAGE_SIZE 512
+#endif
+#define ERASE_BLOCK 16384
+
+;; GPIO pins connected to NAND flash
+#define CE 4
+#define CLE 5
+#define ALE 6
+#define BY 7
+
+;; Address space for NAND flash
+#define NAND_RD_ADDR 0x90000000
+#define NAND_WR_ADDR 0x94000000
+
+#define READ_CMD 0x00
+
+;; Readability macros
+#define CSP_MASK \
+ REG_MASK(bif_core, rw_grp3_cfg, gated_csp0) | \
+ REG_MASK(bif_core, rw_grp3_cfg, gated_csp1)
+#define CSP_VAL \
+ REG_STATE(bif_core, rw_grp3_cfg, gated_csp0, rd) | \
+ REG_STATE(bif_core, rw_grp3_cfg, gated_csp1, wr)
+
+;;----------------------------------------------------------------------------
+;; Macros to set/clear GPIO bits
+
+.macro SET x
+ or.b (1<<\x),$r9
+ move.d $r9, [$r2]
+.endm
+
+.macro CLR x
+ and.b ~(1<<\x),$r9
+ move.d $r9, [$r2]
+.endm
+
+;;----------------------------------------------------------------------------
+
+nand_boot:
+ ;; Check if nand boot was selected
+ move.d REG_ADDR(config, regi_config, r_bootsel), $r0
+ move.d [$r0], $r0
+ and.d REG_MASK(config, r_bootsel, boot_mode), $r0
+ cmp.d REG_STATE(config, r_bootsel, boot_mode, nand), $r0
+ bne normal_boot ; No NAND boot
+ nop
+
+copy_nand_to_ram:
+ ;; copy_nand_to_ram
+ ;; Arguments
+ ;; r10 - destination
+ ;; r11 - source offset
+ ;; r12 - size
+ ;; r13 - Address to jump to after completion
+ ;; Note : r10-r12 are clobbered on return
+ ;; Registers used:
+ ;; r0 - NAND_RD_ADDR
+ ;; r1 - NAND_WR_ADDR
+ ;; r2 - reg_gio_rw_pa_dout
+ ;; r3 - reg_gio_r_pa_din
+ ;; r4 - tmp
+ ;; r5 - byte counter within a page
+ ;; r6 - reg_pinmux_rw_pa
+ ;; r7 - reg_gio_rw_pa_oe
+ ;; r8 - reg_bif_core_rw_grp3_cfg
+ ;; r9 - reg_gio_rw_pa_dout shadow
+ move.d 0x90000000, $r0
+ move.d 0x94000000, $r1
+ move.d REG_ADDR(gio, regi_gio, rw_pa_dout), $r2
+ move.d REG_ADDR(gio, regi_gio, r_pa_din), $r3
+ move.d REG_ADDR(pinmux, regi_pinmux, rw_pa), $r6
+ move.d REG_ADDR(gio, regi_gio, rw_pa_oe), $r7
+ move.d REG_ADDR(bif_core, regi_bif_core, rw_grp3_cfg), $r8
+
+#if CONFIG_ETRAX_FLASH_BUSWIDTH==2
+ lsrq 1, $r11
+#endif
+ ;; Set up GPIO
+ move.d [$r2], $r9
+ move.d [$r7], $r4
+ or.b (1<<ALE) | (1 << CLE) | (1<<CE), $r4
+ move.d $r4, [$r7]
+
+ ;; Set up bif
+ move.d [$r8], $r4
+ and.d CSP_MASK, $r4
+ or.d CSP_VAL, $r4
+ move.d $r4, [$r8]
+
+1: ;; Copy one page
+ CLR CE
+ SET CLE
+ moveq READ_CMD, $r4
+ move.b $r4, [$r1]
+ moveq 20, $r4
+2: bne 2b
+ subq 1, $r4
+ CLR CLE
+ SET ALE
+ clear.w [$r1] ; Column address = 0
+ move.d $r11, $r4
+ lsrq 8, $r4
+ move.b $r4, [$r1] ; Row address
+ lsrq 8, $r4
+ move.b $r4, [$r1] ; Row adddress
+ moveq 20, $r4
+2: bne 2b
+ subq 1, $r4
+ CLR ALE
+2: move.d [$r3], $r4
+ and.d 1 << BY, $r4
+ beq 2b
+ movu.w PAGE_SIZE, $r5
+2: ; Copy one byte/word
+#if CONFIG_ETRAX_FLASH_BUSWIDTH==2
+ move.w [$r0], $r4
+#else
+ move.b [$r0], $r4
+#endif
+ subq 1, $r5
+ bne 2b
+#if CONFIG_ETRAX_FLASH_BUSWIDTH==2
+ move.w $r4, [$r10+]
+ subu.w PAGE_SIZE*2, $r12
+#else
+ move.b $r4, [$r10+]
+ subu.w PAGE_SIZE, $r12
+#endif
+ bpl 1b
+ addu.w PAGE_SIZE, $r11
+
+ ;; End of copy
+ jump $r13
+ nop
+
+ ;; This will warn if the code above is too large. If you consider
+ ;; to remove this you don't understand the bug/feature.
+ .org 256
+ .org ERASE_BLOCK
+
+normal_boot:
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