tridentfb: fix console freeze when switching from X11

This patch fixes two problems when acceleration is enabled:

 - console switch from the Xorg locks up the computer
   because the Xorg code locks some registers and disables
   the mmio mode, so reenable these in the
   tridentfb_set_par() and enable_mmio()

 - blacklist the Image975 chipset from setting PCI burst
   mode. This helps with random lock ups of the
   framebuffer on this chip. The same fix is probably
   needed for the Xorg as well.
Signed-off-by: NKrzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/tridentfb.c

@@ -558,13 +558,15 @@ static inline void write3CE(struct tridentfb_par *par, int reg,
 	vga_mm_wgfx(par->io_virt, reg, val);
 }
 
-static void enable_mmio(void)
+static void enable_mmio(struct tridentfb_par *par)
 {
 	/* Goto New Mode */
 	vga_io_rseq(0x0B);
 
 	/* Unprotect registers */
 	vga_io_wseq(NewMode1, 0x80);
+	if (!is_oldprotect(par->chip_id))
+		vga_io_wseq(Protection, 0x92);
 
 	/* Enable MMIO */
 	outb(PCIReg, 0x3D4);
@@ -578,6 +580,8 @@ static void disable_mmio(struct tridentfb_par *par)
 
 	/* Unprotect registers */
 	vga_mm_wseq(par->io_virt, NewMode1, 0x80);
+	if (!is_oldprotect(par->chip_id))
+		vga_mm_wseq(par->io_virt, Protection, 0x92);
 
 	/* Disable MMIO */
 	t_outb(par, PCIReg, 0x3D4);
@@ -995,6 +999,7 @@ static int tridentfb_set_par(struct fb_info *info)
 		vblankend /= 2;
 	}
 
+	enable_mmio(par);
 	crtc_unlock(par);
 	write3CE(par, CyberControl, 8);
 	tmp = 0xEB;
@@ -1116,7 +1121,7 @@ static int tridentfb_set_par(struct fb_info *info)
 	if (!is_xp(par->chip_id))
 		write3X4(par, Performance, read3X4(par, Performance) | 0x10);
 	/* MMIO & PCI read and write burst enable */
-	if (par->chip_id != TGUI9440)
+	if (par->chip_id != TGUI9440 && par->chip_id != IMAGE975)
 		write3X4(par, PCIReg, read3X4(par, PCIReg) | 0x06);
 
 	vga_mm_wseq(par->io_virt, 0, 3);
@@ -1403,7 +1408,7 @@ static int __devinit trident_pci_probe(struct pci_dev *dev,
 		goto out_unmap1;
 	}
 
-	enable_mmio();
+	enable_mmio(default_par);
 
 	/* setup framebuffer memory */
 	tridentfb_fix.smem_start = pci_resource_start(dev, 0);