cirrusfb: check_par fixes

1. Check if virtual resolution fits into memory.
   Otherwise, Linux hangs during panning.
2. When selected use all available memory to
    maximize yres_virtual to speed up panning
   (previously also xres_virtual was increased).
3. Simplify memory restriction calculations.

Signed-off-by: Krzysztof Helt <krzysztof.h1@poczta.fm>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/video/cirrusfb.c b/drivers/video/cirrusfb.c
index c14b243..e729fb2 100644 (file)
--- a/drivers/video/cirrusfb.c
+++ b/drivers/video/cirrusfb.c
@@ -628,27 +628,18 @@ static long cirrusfb_get_mclk(long freq, int bpp, long *div)
 static int cirrusfb_check_var(struct fb_var_screeninfo *var,
                              struct fb_info *info)
 {
-       int nom, den;           /* translyting from pixels->bytes */
-       int yres, i;
-       static struct { int xres, yres; } modes[] =
-       { { 1600, 1280 },
-         { 1280, 1024 },
-         { 1024, 768 },
-         { 800, 600 },
-         { 640, 480 },
-         { -1, -1 } };
+       int yres;
+       /* memory size in pixels */
+       unsigned pixels = info->screen_size * 8 / var->bits_per_pixel;
 
        switch (var->bits_per_pixel) {
        case 1:
-               nom = 4;
-               den = 8;
+               pixels /= 4;
                break;          /* 8 pixel per byte, only 1/4th of mem usable */
        case 8:
        case 16:
        case 24:
        case 32:
-               nom = var->bits_per_pixel / 8;
-               den = 1;
                break;          /* 1 pixel == 1 byte */
        default:
                printk(KERN_ERR "cirrusfb: mode %dx%dx%d rejected..."
@@ -658,43 +649,29 @@ static int cirrusfb_check_var(struct fb_var_screeninfo *var,
                return -EINVAL;
        }
 
-       if (var->xres * nom / den * var->yres > info->screen_size) {
-               printk(KERN_ERR "cirrusfb: mode %dx%dx%d rejected..."
-                       "resolution too high to fit into video memory!\n",
-                       var->xres, var->yres, var->bits_per_pixel);
-               DPRINTK("EXIT - EINVAL error\n");
-               return -EINVAL;
-       }
-
+       if (var->xres_virtual < var->xres)
+               var->xres_virtual = var->xres;
        /* use highest possible virtual resolution */
-       if (var->xres_virtual == -1 &&
-           var->yres_virtual == -1) {
-               printk(KERN_INFO
-                    "cirrusfb: using maximum available virtual resolution\n");
-               for (i = 0; modes[i].xres != -1; i++) {
-                       int size = modes[i].xres * nom / den * modes[i].yres;
-                       if (size < info->screen_size / 2)
-                               break;
-               }
-               if (modes[i].xres == -1) {
-                       printk(KERN_ERR "cirrusfb: could not find a virtual "
-                               "resolution that fits into video memory!!\n");
-                       DPRINTK("EXIT - EINVAL error\n");
-                       return -EINVAL;
-               }
-               var->xres_virtual = modes[i].xres;
-               var->yres_virtual = modes[i].yres;
+       if (var->yres_virtual == -1) {
+               var->yres_virtual = pixels / var->xres_virtual;
 
                printk(KERN_INFO "cirrusfb: virtual resolution set to "
                        "maximum of %dx%d\n", var->xres_virtual,
                        var->yres_virtual);
        }
-
-       if (var->xres_virtual < var->xres)
-               var->xres_virtual = var->xres;
        if (var->yres_virtual < var->yres)
                var->yres_virtual = var->yres;
 
+       if (var->xres_virtual * var->yres_virtual > pixels) {
+               printk(KERN_ERR "cirrusfb: mode %dx%dx%d rejected... "
+                     "virtual resolution too high to fit into video memory!\n",
+                       var->xres_virtual, var->yres_virtual,
+                       var->bits_per_pixel);
+               DPRINTK("EXIT - EINVAL error\n");
+               return -EINVAL;
+       }
+
+
        if (var->xoffset < 0)
                var->xoffset = 0;
        if (var->yoffset < 0)