gwj / at91sam9263 · Files

/*

 * QEMU VGA Emulator.

 *

 * Copyright (c) 2003 Fabrice Bellard

 *

 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "hw.h"
#include "console.h"
#include "pc.h"
#include "pci.h"

#include "vga_int.h"

#include "pixel_ops.h"

#include "qemu-timer.h"

//#define DEBUG_VGA

//#define DEBUG_VGA_MEM

//#define DEBUG_VGA_REG

//#define DEBUG_BOCHS_VBE

/* force some bits to zero */

const uint8_t sr_mask[8] = {

    (uint8_t)~0xfc,
    (uint8_t)~0xc2,
    (uint8_t)~0xf0,
    (uint8_t)~0xc0,
    (uint8_t)~0xf1,
    (uint8_t)~0xff,
    (uint8_t)~0xff,
    (uint8_t)~0x00,
};

const uint8_t gr_mask[16] = {

    (uint8_t)~0xf0, /* 0x00 */
    (uint8_t)~0xf0, /* 0x01 */
    (uint8_t)~0xf0, /* 0x02 */
    (uint8_t)~0xe0, /* 0x03 */
    (uint8_t)~0xfc, /* 0x04 */
    (uint8_t)~0x84, /* 0x05 */
    (uint8_t)~0xf0, /* 0x06 */
    (uint8_t)~0xf0, /* 0x07 */
    (uint8_t)~0x00, /* 0x08 */
    (uint8_t)~0xff, /* 0x09 */
    (uint8_t)~0xff, /* 0x0a */
    (uint8_t)~0xff, /* 0x0b */
    (uint8_t)~0xff, /* 0x0c */
    (uint8_t)~0xff, /* 0x0d */
    (uint8_t)~0xff, /* 0x0e */
    (uint8_t)~0xff, /* 0x0f */
};

#define cbswap_32(__x) \
((uint32_t)( \
		(((uint32_t)(__x) & (uint32_t)0x000000ffUL) << 24) | \
		(((uint32_t)(__x) & (uint32_t)0x0000ff00UL) <<  8) | \
		(((uint32_t)(__x) & (uint32_t)0x00ff0000UL) >>  8) | \
		(((uint32_t)(__x) & (uint32_t)0xff000000UL) >> 24) ))

#ifdef WORDS_BIGENDIAN

#define PAT(x) cbswap_32(x)
#else
#define PAT(x) (x)
#endif

#ifdef WORDS_BIGENDIAN
#define BIG 1
#else
#define BIG 0
#endif

#ifdef WORDS_BIGENDIAN
#define GET_PLANE(data, p) (((data) >> (24 - (p) * 8)) & 0xff)
#else
#define GET_PLANE(data, p) (((data) >> ((p) * 8)) & 0xff)
#endif

static const uint32_t mask16[16] = {
    PAT(0x00000000),
    PAT(0x000000ff),
    PAT(0x0000ff00),
    PAT(0x0000ffff),
    PAT(0x00ff0000),
    PAT(0x00ff00ff),
    PAT(0x00ffff00),
    PAT(0x00ffffff),
    PAT(0xff000000),
    PAT(0xff0000ff),
    PAT(0xff00ff00),
    PAT(0xff00ffff),
    PAT(0xffff0000),
    PAT(0xffff00ff),
    PAT(0xffffff00),
    PAT(0xffffffff),
};

#undef PAT

#ifdef WORDS_BIGENDIAN

#define PAT(x) (x)
#else
#define PAT(x) cbswap_32(x)
#endif

static const uint32_t dmask16[16] = {
    PAT(0x00000000),
    PAT(0x000000ff),
    PAT(0x0000ff00),
    PAT(0x0000ffff),
    PAT(0x00ff0000),
    PAT(0x00ff00ff),
    PAT(0x00ffff00),
    PAT(0x00ffffff),
    PAT(0xff000000),
    PAT(0xff0000ff),
    PAT(0xff00ff00),
    PAT(0xff00ffff),
    PAT(0xffff0000),
    PAT(0xffff00ff),
    PAT(0xffffff00),
    PAT(0xffffffff),
};

static const uint32_t dmask4[4] = {
    PAT(0x00000000),
    PAT(0x0000ffff),
    PAT(0xffff0000),
    PAT(0xffffffff),
};

static uint32_t expand4[256];
static uint16_t expand2[256];

static uint8_t expand4to8[16];

static void vga_screen_dump(void *opaque, const char *filename);

static void vga_dumb_update_retrace_info(VGAState *s)
{
    (void) s;
}

static void vga_precise_update_retrace_info(VGAState *s)
{
    int htotal_chars;
    int hretr_start_char;
    int hretr_skew_chars;
    int hretr_end_char;

    int vtotal_lines;
    int vretr_start_line;
    int vretr_end_line;

    int div2, sldiv2, dots;
    int clocking_mode;
    int clock_sel;
    const int hz[] = {25175000, 28322000, 25175000, 25175000};
    int64_t chars_per_sec;
    struct vga_precise_retrace *r = &s->retrace_info.precise;

    htotal_chars = s->cr[0x00] + 5;
    hretr_start_char = s->cr[0x04];
    hretr_skew_chars = (s->cr[0x05] >> 5) & 3;
    hretr_end_char = s->cr[0x05] & 0x1f;

    vtotal_lines = (s->cr[0x06]
                    | (((s->cr[0x07] & 1) | ((s->cr[0x07] >> 4) & 2)) << 8)) + 2
        ;
    vretr_start_line = s->cr[0x10]
        | ((((s->cr[0x07] >> 2) & 1) | ((s->cr[0x07] >> 6) & 2)) << 8)
        ;
    vretr_end_line = s->cr[0x11] & 0xf;


    div2 = (s->cr[0x17] >> 2) & 1;
    sldiv2 = (s->cr[0x17] >> 3) & 1;

    clocking_mode = (s->sr[0x01] >> 3) & 1;
    clock_sel = (s->msr >> 2) & 3;

    dots = (s->msr & 1) ? 8 : 9;

    chars_per_sec = hz[clock_sel] / dots;

    htotal_chars <<= clocking_mode;

    r->total_chars = vtotal_lines * htotal_chars;
    r->total_chars = (vretr_start_line + vretr_end_line + 1) * htotal_chars;
    if (r->freq) {
        r->ticks_per_char = ticks_per_sec / (r->total_chars * r->freq);
    } else {
        r->ticks_per_char = ticks_per_sec / chars_per_sec;
    }

    r->vstart = vretr_start_line;
    r->vend = r->vstart + vretr_end_line + 1;

    r->hstart = hretr_start_char + hretr_skew_chars;
    r->hend = r->hstart + hretr_end_char + 1;
    r->htotal = htotal_chars;

#if 0

    printf("hz=%f\n",
    printf (

        "hz=%f\n"

        "htotal = %d\n"
        "hretr_start = %d\n"
        "hretr_skew = %d\n"
        "hretr_end = %d\n"
        "vtotal = %d\n"
        "vretr_start = %d\n"
        "vretr_end = %d\n"
        "div2 = %d sldiv2 = %d\n"
        "clocking_mode = %d\n"
        "clock_sel = %d %d\n"
        "dots = %d\n"
        "ticks/char = %lld\n"
        "\n",

        (double) ticks_per_sec / (r->ticks_per_char * r->total_chars),

        htotal_chars,
        hretr_start_char,
        hretr_skew_chars,
        hretr_end_char,
        vtotal_lines,
        vretr_start_line,
        vretr_end_line,
        div2, sldiv2,
        clocking_mode,
        clock_sel,
        hz[clock_sel],
        dots,
        r->ticks_per_char
        );
#endif
}

static uint8_t vga_precise_retrace(VGAState *s)
{
    struct vga_precise_retrace *r = &s->retrace_info.precise;
    uint8_t val = s->st01 & ~(ST01_V_RETRACE | ST01_DISP_ENABLE);

    if (r->total_chars) {
        int cur_line, cur_line_char, cur_char;
        int64_t cur_tick;

        cur_tick = qemu_get_clock(vm_clock);

        cur_char = (cur_tick / r->ticks_per_char) % r->total_chars;
        cur_line = cur_char / r->htotal;

        if (cur_line >= r->vstart && cur_line <= r->vend) {
            val |= ST01_V_RETRACE | ST01_DISP_ENABLE;

        } else {
            cur_line_char = cur_char % r->htotal;
            if (cur_line_char >= r->hstart && cur_line_char <= r->hend) {
                val |= ST01_DISP_ENABLE;
            }

        }

        return val;
    } else {
        return s->st01 ^ (ST01_V_RETRACE | ST01_DISP_ENABLE);
    }
}

static uint8_t vga_dumb_retrace(VGAState *s)
{
    return s->st01 ^ (ST01_V_RETRACE | ST01_DISP_ENABLE);
}

static uint32_t vga_ioport_read(void *opaque, uint32_t addr)

{

    VGAState *s = opaque;

    int val, index;

    /* check port range access depending on color/monochrome mode */
    if ((addr >= 0x3b0 && addr <= 0x3bf && (s->msr & MSR_COLOR_EMULATION)) ||
        (addr >= 0x3d0 && addr <= 0x3df && !(s->msr & MSR_COLOR_EMULATION))) {
        val = 0xff;
    } else {
        switch(addr) {
        case 0x3c0:
            if (s->ar_flip_flop == 0) {
                val = s->ar_index;
            } else {
                val = 0;
            }
            break;
        case 0x3c1:
            index = s->ar_index & 0x1f;

            if (index < 21)

                val = s->ar[index];
            else
                val = 0;
            break;
        case 0x3c2:
            val = s->st00;
            break;
        case 0x3c4:
            val = s->sr_index;
            break;
        case 0x3c5:
            val = s->sr[s->sr_index];

#ifdef DEBUG_VGA_REG
            printf("vga: read SR%x = 0x%02x\n", s->sr_index, val);
#endif

            break;
        case 0x3c7:
            val = s->dac_state;
            break;

	case 0x3c8:
	    val = s->dac_write_index;
	    break;

        case 0x3c9:
            val = s->palette[s->dac_read_index * 3 + s->dac_sub_index];
            if (++s->dac_sub_index == 3) {
                s->dac_sub_index = 0;
                s->dac_read_index++;
            }
            break;
        case 0x3ca:
            val = s->fcr;
            break;
        case 0x3cc:
            val = s->msr;
            break;
        case 0x3ce:
            val = s->gr_index;
            break;
        case 0x3cf:
            val = s->gr[s->gr_index];

#ifdef DEBUG_VGA_REG
            printf("vga: read GR%x = 0x%02x\n", s->gr_index, val);
#endif

            break;
        case 0x3b4:
        case 0x3d4:
            val = s->cr_index;
            break;
        case 0x3b5:
        case 0x3d5:
            val = s->cr[s->cr_index];

#ifdef DEBUG_VGA_REG
            printf("vga: read CR%x = 0x%02x\n", s->cr_index, val);
#endif

            break;
        case 0x3ba:
        case 0x3da:
            /* just toggle to fool polling */

            val = s->st01 = s->retrace(s);

            s->ar_flip_flop = 0;
            break;
        default:
            val = 0x00;
            break;
        }
    }

#if defined(DEBUG_VGA)

    printf("VGA: read addr=0x%04x data=0x%02x\n", addr, val);
#endif
    return val;
}

static void vga_ioport_write(void *opaque, uint32_t addr, uint32_t val)

{

    VGAState *s = opaque;

    int index;

    /* check port range access depending on color/monochrome mode */
    if ((addr >= 0x3b0 && addr <= 0x3bf && (s->msr & MSR_COLOR_EMULATION)) ||
        (addr >= 0x3d0 && addr <= 0x3df && !(s->msr & MSR_COLOR_EMULATION)))
        return;

#ifdef DEBUG_VGA
    printf("VGA: write addr=0x%04x data=0x%02x\n", addr, val);
#endif

    switch(addr) {
    case 0x3c0:
        if (s->ar_flip_flop == 0) {
            val &= 0x3f;
            s->ar_index = val;
        } else {
            index = s->ar_index & 0x1f;
            switch(index) {
            case 0x00 ... 0x0f:
                s->ar[index] = val & 0x3f;
                break;
            case 0x10:
                s->ar[index] = val & ~0x10;
                break;
            case 0x11:
                s->ar[index] = val;
                break;
            case 0x12:
                s->ar[index] = val & ~0xc0;
                break;
            case 0x13:
                s->ar[index] = val & ~0xf0;
                break;
            case 0x14:
                s->ar[index] = val & ~0xf0;
                break;
            default:
                break;
            }
        }
        s->ar_flip_flop ^= 1;
        break;
    case 0x3c2:
        s->msr = val & ~0x10;

        s->update_retrace_info(s);

        break;
    case 0x3c4:
        s->sr_index = val & 7;
        break;
    case 0x3c5:

#ifdef DEBUG_VGA_REG
        printf("vga: write SR%x = 0x%02x\n", s->sr_index, val);
#endif

        s->sr[s->sr_index] = val & sr_mask[s->sr_index];

        if (s->sr_index == 1) s->update_retrace_info(s);

        break;
    case 0x3c7:
        s->dac_read_index = val;
        s->dac_sub_index = 0;
        s->dac_state = 3;
        break;
    case 0x3c8:
        s->dac_write_index = val;
        s->dac_sub_index = 0;
        s->dac_state = 0;
        break;
    case 0x3c9:
        s->dac_cache[s->dac_sub_index] = val;
        if (++s->dac_sub_index == 3) {
            memcpy(&s->palette[s->dac_write_index * 3], s->dac_cache, 3);
            s->dac_sub_index = 0;
            s->dac_write_index++;
        }
        break;
    case 0x3ce:
        s->gr_index = val & 0x0f;
        break;
    case 0x3cf:

#ifdef DEBUG_VGA_REG
        printf("vga: write GR%x = 0x%02x\n", s->gr_index, val);
#endif

        s->gr[s->gr_index] = val & gr_mask[s->gr_index];
        break;
    case 0x3b4:
    case 0x3d4:
        s->cr_index = val;
        break;
    case 0x3b5:
    case 0x3d5:

#ifdef DEBUG_VGA_REG
        printf("vga: write CR%x = 0x%02x\n", s->cr_index, val);
#endif

        /* handle CR0-7 protection */

        if ((s->cr[0x11] & 0x80) && s->cr_index <= 7) {

            /* can always write bit 4 of CR7 */
            if (s->cr_index == 7)
                s->cr[7] = (s->cr[7] & ~0x10) | (val & 0x10);
            return;
        }
        switch(s->cr_index) {
        case 0x01: /* horizontal display end */
        case 0x07:
        case 0x09:
        case 0x0c:
        case 0x0d:

        case 0x12: /* vertical display end */

            s->cr[s->cr_index] = val;
            break;
        default:
            s->cr[s->cr_index] = val;
            break;
        }

        switch(s->cr_index) {
        case 0x00:
        case 0x04:
        case 0x05:
        case 0x06:
        case 0x07:
        case 0x11:
        case 0x17:
            s->update_retrace_info(s);
            break;
        }

        break;
    case 0x3ba:
    case 0x3da:
        s->fcr = val & 0x10;
        break;
    }
}

#ifdef CONFIG_BOCHS_VBE

static uint32_t vbe_ioport_read_index(void *opaque, uint32_t addr)

{

    VGAState *s = opaque;

    uint32_t val;

    val = s->vbe_index;
    return val;
}

static uint32_t vbe_ioport_read_data(void *opaque, uint32_t addr)
{
    VGAState *s = opaque;
    uint32_t val;

    if (s->vbe_index <= VBE_DISPI_INDEX_NB) {
        if (s->vbe_regs[VBE_DISPI_INDEX_ENABLE] & VBE_DISPI_GETCAPS) {
            switch(s->vbe_index) {
                /* XXX: do not hardcode ? */
            case VBE_DISPI_INDEX_XRES:
                val = VBE_DISPI_MAX_XRES;
                break;
            case VBE_DISPI_INDEX_YRES:
                val = VBE_DISPI_MAX_YRES;
                break;
            case VBE_DISPI_INDEX_BPP:
                val = VBE_DISPI_MAX_BPP;
                break;
            default:

                val = s->vbe_regs[s->vbe_index];

                break;
            }
        } else {

            val = s->vbe_regs[s->vbe_index];

        }
    } else {

        val = 0;

    }

#ifdef DEBUG_BOCHS_VBE

    printf("VBE: read index=0x%x val=0x%x\n", s->vbe_index, val);

#endif
    return val;
}

static void vbe_ioport_write_index(void *opaque, uint32_t addr, uint32_t val)
{
    VGAState *s = opaque;
    s->vbe_index = val;
}

static void vbe_ioport_write_data(void *opaque, uint32_t addr, uint32_t val)

{

    VGAState *s = opaque;

    if (s->vbe_index <= VBE_DISPI_INDEX_NB) {

#ifdef DEBUG_BOCHS_VBE
        printf("VBE: write index=0x%x val=0x%x\n", s->vbe_index, val);
#endif
        switch(s->vbe_index) {
        case VBE_DISPI_INDEX_ID:

            if (val == VBE_DISPI_ID0 ||
                val == VBE_DISPI_ID1 ||

                val == VBE_DISPI_ID2 ||
                val == VBE_DISPI_ID3 ||
                val == VBE_DISPI_ID4) {

                s->vbe_regs[s->vbe_index] = val;
            }

            break;
        case VBE_DISPI_INDEX_XRES:

            if ((val <= VBE_DISPI_MAX_XRES) && ((val & 7) == 0)) {
                s->vbe_regs[s->vbe_index] = val;
            }

            break;
        case VBE_DISPI_INDEX_YRES:

            if (val <= VBE_DISPI_MAX_YRES) {
                s->vbe_regs[s->vbe_index] = val;
            }

            break;
        case VBE_DISPI_INDEX_BPP:
            if (val == 0)
                val = 8;

            if (val == 4 || val == 8 || val == 15 ||

                val == 16 || val == 24 || val == 32) {
                s->vbe_regs[s->vbe_index] = val;
            }

            break;
        case VBE_DISPI_INDEX_BANK:

            if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) {
              val &= (s->vbe_bank_mask >> 2);
            } else {
              val &= s->vbe_bank_mask;
            }

            s->vbe_regs[s->vbe_index] = val;

            s->bank_offset = (val << 16);

            break;
        case VBE_DISPI_INDEX_ENABLE:

            if ((val & VBE_DISPI_ENABLED) &&
                !(s->vbe_regs[VBE_DISPI_INDEX_ENABLE] & VBE_DISPI_ENABLED)) {

                int h, shift_control;

                s->vbe_regs[VBE_DISPI_INDEX_VIRT_WIDTH] =

                    s->vbe_regs[VBE_DISPI_INDEX_XRES];

                s->vbe_regs[VBE_DISPI_INDEX_VIRT_HEIGHT] =

                    s->vbe_regs[VBE_DISPI_INDEX_YRES];
                s->vbe_regs[VBE_DISPI_INDEX_X_OFFSET] = 0;
                s->vbe_regs[VBE_DISPI_INDEX_Y_OFFSET] = 0;

                if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4)
                    s->vbe_line_offset = s->vbe_regs[VBE_DISPI_INDEX_XRES] >> 1;
                else

                    s->vbe_line_offset = s->vbe_regs[VBE_DISPI_INDEX_XRES] *

                        ((s->vbe_regs[VBE_DISPI_INDEX_BPP] + 7) >> 3);
                s->vbe_start_addr = 0;

                /* clear the screen (should be done in BIOS) */
                if (!(val & VBE_DISPI_NOCLEARMEM)) {

                    memset(s->vram_ptr, 0,

                           s->vbe_regs[VBE_DISPI_INDEX_YRES] * s->vbe_line_offset);
                }

                /* we initialize the VGA graphic mode (should be done
                   in BIOS) */
                s->gr[0x06] = (s->gr[0x06] & ~0x0c) | 0x05; /* graphic mode + memory map 1 */

                s->cr[0x17] |= 3; /* no CGA modes */
                s->cr[0x13] = s->vbe_line_offset >> 3;
                /* width */
                s->cr[0x01] = (s->vbe_regs[VBE_DISPI_INDEX_XRES] >> 3) - 1;

                /* height (only meaningful if < 1024) */

                h = s->vbe_regs[VBE_DISPI_INDEX_YRES] - 1;
                s->cr[0x12] = h;

                s->cr[0x07] = (s->cr[0x07] & ~0x42) |

                    ((h >> 7) & 0x02) | ((h >> 3) & 0x40);
                /* line compare to 1023 */
                s->cr[0x18] = 0xff;
                s->cr[0x07] |= 0x10;
                s->cr[0x09] |= 0x40;

                if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) {
                    shift_control = 0;
                    s->sr[0x01] &= ~8; /* no double line */
                } else {
                    shift_control = 2;

                    s->sr[4] |= 0x08; /* set chain 4 mode */

                    s->sr[2] |= 0x0f; /* activate all planes */

                }
                s->gr[0x05] = (s->gr[0x05] & ~0x60) | (shift_control << 5);
                s->cr[0x09] &= ~0x9f; /* no double scan */

            } else {
                /* XXX: the bios should do that */

                s->bank_offset = 0;

            }

            s->dac_8bit = (val & VBE_DISPI_8BIT_DAC) > 0;

            s->vbe_regs[s->vbe_index] = val;

            break;
        case VBE_DISPI_INDEX_VIRT_WIDTH:
            {
                int w, h, line_offset;

                if (val < s->vbe_regs[VBE_DISPI_INDEX_XRES])
                    return;
                w = val;
                if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4)
                    line_offset = w >> 1;
                else
                    line_offset = w * ((s->vbe_regs[VBE_DISPI_INDEX_BPP] + 7) >> 3);
                h = s->vram_size / line_offset;
                /* XXX: support weird bochs semantics ? */
                if (h < s->vbe_regs[VBE_DISPI_INDEX_YRES])
                    return;
                s->vbe_regs[VBE_DISPI_INDEX_VIRT_WIDTH] = w;
                s->vbe_regs[VBE_DISPI_INDEX_VIRT_HEIGHT] = h;
                s->vbe_line_offset = line_offset;
            }
            break;
        case VBE_DISPI_INDEX_X_OFFSET:
        case VBE_DISPI_INDEX_Y_OFFSET:
            {
                int x;
                s->vbe_regs[s->vbe_index] = val;
                s->vbe_start_addr = s->vbe_line_offset * s->vbe_regs[VBE_DISPI_INDEX_Y_OFFSET];
                x = s->vbe_regs[VBE_DISPI_INDEX_X_OFFSET];
                if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4)
                    s->vbe_start_addr += x >> 1;
                else
                    s->vbe_start_addr += x * ((s->vbe_regs[VBE_DISPI_INDEX_BPP] + 7) >> 3);
                s->vbe_start_addr >>= 2;

            }
            break;
        default:
            break;
        }
    }
}
#endif

/* called for accesses between 0xa0000 and 0xc0000 */

uint32_t vga_mem_readb(void *opaque, target_phys_addr_t addr)

{

    VGAState *s = opaque;

    int memory_map_mode, plane;
    uint32_t ret;

    /* convert to VGA memory offset */
    memory_map_mode = (s->gr[6] >> 2) & 3;

    addr &= 0x1ffff;

    switch(memory_map_mode) {
    case 0:
        break;
    case 1:

        if (addr >= 0x10000)

            return 0xff;

        addr += s->bank_offset;

        break;
    case 2:

        addr -= 0x10000;

        if (addr >= 0x8000)
            return 0xff;
        break;
    default:
    case 3:

        addr -= 0x18000;

        if (addr >= 0x8000)
            return 0xff;

        break;
    }

    if (s->sr[4] & 0x08) {
        /* chain 4 mode : simplest access */
        ret = s->vram_ptr[addr];
    } else if (s->gr[5] & 0x10) {
        /* odd/even mode (aka text mode mapping) */
        plane = (s->gr[4] & 2) | (addr & 1);
        ret = s->vram_ptr[((addr & ~1) << 1) | plane];
    } else {
        /* standard VGA latched access */
        s->latch = ((uint32_t *)s->vram_ptr)[addr];

        if (!(s->gr[5] & 0x08)) {
            /* read mode 0 */
            plane = s->gr[4];

            ret = GET_PLANE(s->latch, plane);

        } else {
            /* read mode 1 */
            ret = (s->latch ^ mask16[s->gr[2]]) & mask16[s->gr[7]];
            ret |= ret >> 16;
            ret |= ret >> 8;
            ret = (~ret) & 0xff;
        }
    }
    return ret;
}

static uint32_t vga_mem_readw(void *opaque, target_phys_addr_t addr)

{
    uint32_t v;

#ifdef TARGET_WORDS_BIGENDIAN

    v = vga_mem_readb(opaque, addr) << 8;
    v |= vga_mem_readb(opaque, addr + 1);

#else

    v = vga_mem_readb(opaque, addr);
    v |= vga_mem_readb(opaque, addr + 1) << 8;

#endif

    return v;
}

static uint32_t vga_mem_readl(void *opaque, target_phys_addr_t addr)

{
    uint32_t v;

#ifdef TARGET_WORDS_BIGENDIAN

    v = vga_mem_readb(opaque, addr) << 24;
    v |= vga_mem_readb(opaque, addr + 1) << 16;
    v |= vga_mem_readb(opaque, addr + 2) << 8;
    v |= vga_mem_readb(opaque, addr + 3);

#else

    v = vga_mem_readb(opaque, addr);
    v |= vga_mem_readb(opaque, addr + 1) << 8;
    v |= vga_mem_readb(opaque, addr + 2) << 16;
    v |= vga_mem_readb(opaque, addr + 3) << 24;