nvidiafb: VGA state save and restore

Allow the saving and restoration of VGA text mode. The state is saved on the
first open and restored on the last close. Because of the non-linear mapping
of the VGA registers to the MMIO space, this will be done only on X86
platforms where the device is the primary display.

An echo 0 > /sys/class/vtconsole/vtcon1/bind will convert the display from
graphics to text mode.

Signed-off-by: Antonino Daplas <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/Makefile

···
 
 obj-$(CONFIG_FB_MATROX)		  += matrox/
 obj-$(CONFIG_FB_RIVA)		  += riva/ vgastate.o
-obj-$(CONFIG_FB_NVIDIA)		  += nvidia/
+obj-$(CONFIG_FB_NVIDIA)		  += nvidia/ vgastate.o
 obj-$(CONFIG_FB_ATY)		  += aty/ macmodes.o
 obj-$(CONFIG_FB_ATY128)		  += aty/ macmodes.o
 obj-$(CONFIG_FB_RADEON)		  += aty/

drivers/video/nvidia/nv_type.h

···
 #include <linux/types.h>
 #include <linux/i2c.h>
 #include <linux/i2c-algo-bit.h>
+#include <linux/mutex.h>
+#include <video/vga.h>
 
 #define NV_ARCH_04  0x04
 #define NV_ARCH_10  0x10
···
 struct nvidia_par {
 	RIVA_HW_STATE SavedReg;
 	RIVA_HW_STATE ModeReg;
+	RIVA_HW_STATE initial_state;
 	RIVA_HW_STATE *CurrentState;
+	struct vgastate vgastate;
+	struct mutex open_lock;
 	u32 pseudo_palette[16];
 	struct pci_dev *pci_dev;
 	u32 Architecture;
···
 	int BlendingPossible;
 	u32 paletteEnabled;
 	u32 forceCRTC;
+	u32 open_count;
 	u8 DDCBase;
 #ifdef CONFIG_MTRR
 	struct {

drivers/video/nvidia/nvidia.c

···
 	return 0;
 }
 
+/*
+ * Because the VGA registers are not mapped linearly in its MMIO space,
+ * restrict VGA register saving and restore to x86 only, where legacy VGA IO
+ * access is legal. Consequently, we must also check if the device is the
+ * primary display.
+ */
+#ifdef CONFIG_X86
+static void save_vga_x86(struct nvidia_par *par)
+{
+	struct resource *res= &par->pci_dev->resource[PCI_ROM_RESOURCE];
+
+	if (res && res->flags & IORESOURCE_ROM_SHADOW) {
+		memset(&par->vgastate, 0, sizeof(par->vgastate));
+		par->vgastate.flags = VGA_SAVE_MODE | VGA_SAVE_FONTS |
+			VGA_SAVE_CMAP;
+		save_vga(&par->vgastate);
+	}
+}
+
+static void restore_vga_x86(struct nvidia_par *par)
+{
+	struct resource *res= &par->pci_dev->resource[PCI_ROM_RESOURCE];
+
+	if (res && res->flags & IORESOURCE_ROM_SHADOW)
+		restore_vga(&par->vgastate);
+}
+#else
+#define save_vga_x86(x) do {} while (0)
+#define restore_vga_x86(x) do {} while (0)
+#endif /* X86 */
+
+static int nvidiafb_open(struct fb_info *info, int user)
+{
+	struct nvidia_par *par = info->par;
+
+	mutex_lock(&par->open_lock);
+
+	if (!par->open_count) {
+		save_vga_x86(par);
+		nvidia_save_vga(par, &par->initial_state);
+	}
+
+	par->open_count++;
+	mutex_unlock(&par->open_lock);
+	return 0;
+}
+
+static int nvidiafb_release(struct fb_info *info, int user)
+{
+	struct nvidia_par *par = info->par;
+	int err = 0;
+
+	mutex_lock(&par->open_lock);
+
+	if (!par->open_count) {
+		err = -EINVAL;
+		goto done;
+	}
+
+	if (par->open_count == 1) {
+		nvidia_write_regs(par, &par->initial_state);
+		restore_vga_x86(par);
+	}
+
+	par->open_count--;
+done:
+	mutex_unlock(&par->open_lock);
+	return 0;
+}
+
 static struct fb_ops nvidia_fb_ops = {
 	.owner          = THIS_MODULE,
+	.fb_open        = nvidiafb_open,
+	.fb_release     = nvidiafb_release,
 	.fb_check_var   = nvidiafb_check_var,
 	.fb_set_par     = nvidiafb_set_par,
 	.fb_setcolreg   = nvidiafb_setcolreg,
···
 
 	par = info->par;
 	par->pci_dev = pd;
-
+	mutex_init(&par->open_lock);
 	info->pixmap.addr = kzalloc(8 * 1024, GFP_KERNEL);
 
 	if (info->pixmap.addr == NULL)