sisfb: limit POST memory test according to PCI resource length

If the POST memory test fails, the driver may access illegal
memory areas. Instead of hard coding the maximum size, set it
according to the PCI resource length (an additional check is needed in
sisfb_post_map_vram() to ensure it's big enough). DRAM sizing will later
adjust video_size to the correct value.
Signed-off-by: NAaro Koskinen <aaro.koskinen@iki.fi>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Signed-off-by: NPaul Mundt <lethal@linux-sh.org>

drivers/video/sis/sis_main.c

@@ -4181,6 +4181,9 @@ static void __devinit
 sisfb_post_map_vram(struct sis_video_info *ivideo, unsigned int *mapsize,
 			unsigned int min)
 {
+	if (*mapsize < (min << 20))
+		return;
+
 	ivideo->video_vbase = ioremap(ivideo->video_base, (*mapsize));
 
 	if(!ivideo->video_vbase) {
@@ -4514,7 +4517,7 @@ sisfb_post_sis300(struct pci_dev *pdev)
 	} else {
 #endif
 		/* Need to map max FB size for finding out about RAM size */
-		mapsize = 64 << 20;
+		mapsize = ivideo->video_size;
 		sisfb_post_map_vram(ivideo, &mapsize, 4);
 
 		if(ivideo->video_vbase) {
@@ -4680,7 +4683,7 @@ sisfb_post_xgi_ramsize(struct sis_video_info *ivideo)
 	orSISIDXREG(SISSR, 0x20, (0x80 | 0x04));
 
 	/* Need to map max FB size for finding out about RAM size */
-	mapsize = 256 << 20;
+	mapsize = ivideo->video_size;
 	sisfb_post_map_vram(ivideo, &mapsize, 32);
 
 	if(!ivideo->video_vbase) {
@@ -5936,6 +5939,7 @@ sisfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	}
 
 	ivideo->video_base = pci_resource_start(pdev, 0);
+	ivideo->video_size = pci_resource_len(pdev, 0);
 	ivideo->mmio_base  = pci_resource_start(pdev, 1);
 	ivideo->mmio_size  = pci_resource_len(pdev, 1);
 	ivideo->SiS_Pr.RelIO = pci_resource_start(pdev, 2) + 0x30;