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x86, setup: Don't skip mode setting for the standard VGA modes 

The code for setting standard VGA modes probes for the current mode,
and skips the mode setting if the mode is 3 (color text 80x25) or 7
(mono text 80x25).  Unfortunately, there are BIOSes, including the
VMware BIOS, which report the previous mode if function 0F is queried
while the screen is in a VESA mode, and of course, nothing can help a
mode poked directly into the hardware.

As such, the safe option is to set the mode anyway, and only query to
see if we should be using mode 7 rather than mode 3.  People who don't
want any mode setting at all should probably use vga=0x0f04
(VIDEO_CURRENT_MODE).  It's possible that should be the kernel
default.

Reported-by Rene Arends <R.R.Arends@hro.nl>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
LKML-Reference: <tip-*@git.kernel.org>
hifive-unleashed-5.1
H. Peter Anvin 2010-02-19 13:21:38 -08:00
parent eb572a5c79
commit 8e92dc767a
1 changed files with 1 additions and 8 deletions
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9
arch/x86/boot/video-vga.c
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@ -42,22 +42,15 @@ static u8 vga_set_basic_mode(void)
{
struct biosregs ireg, oreg;
u16 ax;
u8 rows;
u8 mode;
initregs(&ireg);
/* Query current mode */
ax = 0x0f00;
intcall(0x10, &ireg, &oreg);
mode = oreg.al;
set_fs(0);
rows = rdfs8(0x484); /* rows minus one */
if ((oreg.ax == 0x5003 || oreg.ax == 0x5007) &&
(rows == 0 || rows == 24))
return mode;
if (mode != 3 && mode != 7)
mode = 3;