/* SPDX-License-Identifier: GPL-2.0-only */
/*
 *  linux/arch/arm/lib/ll_char_wr.S
 *
 *  Copyright (C) 1995, 1996 Russell King.
 *
 *  Speedups & 1bpp code (C) 1996 Philip Blundell & Russell King.
 *
 *  10-04-96    RMK     Various cleanups & reduced register usage.
 *  08-04-98    RMK     Shifts re-ordered
 */

@ Regs: [] = corruptible
@       {} = used
@       () = do not use

#include <linux/linkage.h>
#include <asm/assembler.h>
        .text

LC0:    .word   LC0
        .word   bytes_per_char_h
        .word   video_size_row
        .word   acorndata_8x8
        .word   con_charconvtable

/*
 * r0 = ptr
 * r1 = char
 * r2 = white
 */
ENTRY(ll_write_char)
        stmfd   sp!, {r4 - r7, lr}
@
@ Smashable regs: {r0 - r3}, [r4 - r7], (r8 - fp), [ip], (sp), [lr], (pc)
@
        /*
         * calculate offset into character table
         */
        mov     r1, r1, lsl #3
        /*
         * calculate offset required for each row.
         */
        adr     ip, LC0
        ldmia   ip, {r3, r4, r5, r6, lr}
        sub     ip, ip, r3
        add     r6, r6, ip
        add     lr, lr, ip
        ldr     r4, [r4, ip]
        ldr     r5, [r5, ip]
        /*
         * Go to resolution-dependent routine...
         */
        cmp     r4, #4
        blt     Lrow1bpp
        add     r0, r0, r5, lsl #3              @ Move to bottom of character
        orr     r1, r1, #7
        ldrb    r7, [r6, r1]
        teq     r4, #8
        beq     Lrow8bpplp
@
@ Smashable regs: {r0 - r3}, [r4], {r5 - r7}, (r8 - fp), [ip], (sp), {lr}, (pc)
@
Lrow4bpplp:
        ldr     r7, [lr, r7, lsl #2]
        mul     r7, r2, r7
        sub     r1, r1, #1                      @ avoid using r7 directly after
        str     r7, [r0, -r5]!
        ldrb    r7, [r6, r1]
        ldr     r7, [lr, r7, lsl #2]
        mul     r7, r2, r7
        tst     r1, #7                          @ avoid using r7 directly after
        str     r7, [r0, -r5]!
        subne   r1, r1, #1
        ldrbne  r7, [r6, r1]
        bne     Lrow4bpplp
        ldmfd   sp!, {r4 - r7, pc}

@
@ Smashable regs: {r0 - r3}, [r4], {r5 - r7}, (r8 - fp), [ip], (sp), {lr}, (pc)
@
Lrow8bpplp:
        mov     ip, r7, lsr #4
        ldr     ip, [lr, ip, lsl #2]
        mul     r4, r2, ip
        and     ip, r7, #15                     @ avoid r4
        ldr     ip, [lr, ip, lsl #2]            @ avoid r4
        mul     ip, r2, ip                      @ avoid r4
        sub     r1, r1, #1                      @ avoid ip
        sub     r0, r0, r5                      @ avoid ip
        stmia   r0, {r4, ip}
        ldrb    r7, [r6, r1]
        mov     ip, r7, lsr #4
        ldr     ip, [lr, ip, lsl #2]
        mul     r4, r2, ip
        and     ip, r7, #15                     @ avoid r4
        ldr     ip, [lr, ip, lsl #2]            @ avoid r4
        mul     ip, r2, ip                      @ avoid r4
        tst     r1, #7                          @ avoid ip
        sub     r0, r0, r5                      @ avoid ip
        stmia   r0, {r4, ip}
        subne   r1, r1, #1
        ldrbne  r7, [r6, r1]
        bne     Lrow8bpplp
        ldmfd   sp!, {r4 - r7, pc}

@
@ Smashable regs: {r0 - r3}, [r4], {r5, r6}, [r7], (r8 - fp), [ip], (sp), [lr], (pc)
@
Lrow1bpp:
        add     r6, r6, r1
        ldmia   r6, {r4, r7}
        strb    r4, [r0], r5
        mov     r4, r4, lsr #8
        strb    r4, [r0], r5
        mov     r4, r4, lsr #8
        strb    r4, [r0], r5
        mov     r4, r4, lsr #8
        strb    r4, [r0], r5
        strb    r7, [r0], r5
        mov     r7, r7, lsr #8
        strb    r7, [r0], r5
        mov     r7, r7, lsr #8
        strb    r7, [r0], r5
        mov     r7, r7, lsr #8
        strb    r7, [r0], r5
        ldmfd   sp!, {r4 - r7, pc}

        .bss
ENTRY(con_charconvtable)
        .space  1024