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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 26 Apr 2016 15:24:18 +0200
Subject: [PATCH] vga: factor out vga register setup

When enabling vbe mode qemu will setup a bunch of vga registers to make
sure the vga emulation operates in correct mode for a linear
framebuffer.  Move that code to a separate function so we can call it
from other places too.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
(cherry picked from commit 7fa5c2c5dc9f9bf878c1e8669eb9644d70a71e71)
---
 hw/display/vga.c | 78 ++++++++++++++++++++++++++++++++------------------------
 1 file changed, 44 insertions(+), 34 deletions(-)

diff --git a/hw/display/vga.c b/hw/display/vga.c
index 955ad6f..e46a2f8 100644
--- a/hw/display/vga.c
+++ b/hw/display/vga.c
@@ -642,6 +642,49 @@ static void vbe_fixup_regs(VGACommonState *s)
     s->vbe_start_addr  = offset / 4;
 }
 
+/* we initialize the VGA graphic mode */
+static void vbe_update_vgaregs(VGACommonState *s)
+{
+    int h, shift_control;
+
+    if (!vbe_enabled(s)) {
+        /* vbe is turned off -- nothing to do */
+        return;
+    }
+
+    /* graphic mode + memory map 1 */
+    s->gr[VGA_GFX_MISC] = (s->gr[VGA_GFX_MISC] & ~0x0c) | 0x04 |
+        VGA_GR06_GRAPHICS_MODE;
+    s->cr[VGA_CRTC_MODE] |= 3; /* no CGA modes */
+    s->cr[VGA_CRTC_OFFSET] = s->vbe_line_offset >> 3;
+    /* width */
+    s->cr[VGA_CRTC_H_DISP] =
+        (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[VGA_CRTC_V_DISP_END] = h;
+    s->cr[VGA_CRTC_OVERFLOW] = (s->cr[VGA_CRTC_OVERFLOW] & ~0x42) |
+        ((h >> 7) & 0x02) | ((h >> 3) & 0x40);
+    /* line compare to 1023 */
+    s->cr[VGA_CRTC_LINE_COMPARE] = 0xff;
+    s->cr[VGA_CRTC_OVERFLOW] |= 0x10;
+    s->cr[VGA_CRTC_MAX_SCAN] |= 0x40;
+
+    if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) {
+        shift_control = 0;
+        s->sr[VGA_SEQ_CLOCK_MODE] &= ~8; /* no double line */
+    } else {
+        shift_control = 2;
+        /* set chain 4 mode */
+        s->sr[VGA_SEQ_MEMORY_MODE] |= VGA_SR04_CHN_4M;
+        /* activate all planes */
+        s->sr[VGA_SEQ_PLANE_WRITE] |= VGA_SR02_ALL_PLANES;
+    }
+    s->gr[VGA_GFX_MODE] = (s->gr[VGA_GFX_MODE] & ~0x60) |
+        (shift_control << 5);
+    s->cr[VGA_CRTC_MAX_SCAN] &= ~0x9f; /* no double scan */
+}
+
 static uint32_t vbe_ioport_read_index(void *opaque, uint32_t addr)
 {
     VGACommonState *s = opaque;
@@ -728,52 +771,19 @@ void vbe_ioport_write_data(void *opaque, uint32_t addr, uint32_t val)
         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] = 0;
                 s->vbe_regs[VBE_DISPI_INDEX_X_OFFSET] = 0;
                 s->vbe_regs[VBE_DISPI_INDEX_Y_OFFSET] = 0;
                 s->vbe_regs[VBE_DISPI_INDEX_ENABLE] |= VBE_DISPI_ENABLED;
                 vbe_fixup_regs(s);
+                vbe_update_vgaregs(s);
 
                 /* clear the screen */
                 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 */
-                /* graphic mode + memory map 1 */
-                s->gr[VGA_GFX_MISC] = (s->gr[VGA_GFX_MISC] & ~0x0c) | 0x04 |
-                    VGA_GR06_GRAPHICS_MODE;
-                s->cr[VGA_CRTC_MODE] |= 3; /* no CGA modes */
-                s->cr[VGA_CRTC_OFFSET] = s->vbe_line_offset >> 3;
-                /* width */
-                s->cr[VGA_CRTC_H_DISP] =
-                    (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[VGA_CRTC_V_DISP_END] = h;
-                s->cr[VGA_CRTC_OVERFLOW] = (s->cr[VGA_CRTC_OVERFLOW] & ~0x42) |
-                    ((h >> 7) & 0x02) | ((h >> 3) & 0x40);
-                /* line compare to 1023 */
-                s->cr[VGA_CRTC_LINE_COMPARE] = 0xff;
-                s->cr[VGA_CRTC_OVERFLOW] |= 0x10;
-                s->cr[VGA_CRTC_MAX_SCAN] |= 0x40;
-
-                if (s->vbe_regs[VBE_DISPI_INDEX_BPP] == 4) {
-                    shift_control = 0;
-                    s->sr[VGA_SEQ_CLOCK_MODE] &= ~8; /* no double line */
-                } else {
-                    shift_control = 2;
-                    /* set chain 4 mode */
-                    s->sr[VGA_SEQ_MEMORY_MODE] |= VGA_SR04_CHN_4M;
-                    /* activate all planes */
-                    s->sr[VGA_SEQ_PLANE_WRITE] |= VGA_SR02_ALL_PLANES;
-                }
-                s->gr[VGA_GFX_MODE] = (s->gr[VGA_GFX_MODE] & ~0x60) |
-                    (shift_control << 5);
-                s->cr[VGA_CRTC_MAX_SCAN] &= ~0x9f; /* no double scan */
             } else {
                 s->bank_offset = 0;
             }