sisfb: add subroutine for detecting XGI Z9

Z7 and Z9 have the same PCI ID, so additional checking is needed to
detect Z9. The method was "documented" in XGI's xgifb driver.
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Cc: Thomas Winischhofer <thomas@winischhofer.net>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

drivers/video/sis/sis.h

@@ -495,6 +495,7 @@ struct sis_video_info {
 	unsigned int	refresh_rate;
 
 	unsigned int	chip;
+	unsigned int	chip_real_id;
 	u8		revision_id;
 	int		sisvga_enabled;		/* PCI device was enabled */
 

drivers/video/sis/sis_main.c

@@ -4563,6 +4563,11 @@ sisfb_post_sis315330(struct pci_dev *pdev)
 }
 #endif
 
+static inline int sisfb_xgi_is21(struct sis_video_info *ivideo)
+{
+	return ivideo->chip_real_id == XGI_21;
+}
+
 static void __devinit
 sisfb_post_xgi_delay(struct sis_video_info *ivideo, int delay)
 {
@@ -5802,6 +5807,7 @@ sisfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 #endif
 
 	ivideo->chip = chipinfo->chip;
+	ivideo->chip_real_id = chipinfo->chip;
 	ivideo->sisvga_engine = chipinfo->vgaengine;
 	ivideo->hwcursor_size = chipinfo->hwcursor_size;
 	ivideo->CRT2_write_enable = chipinfo->CRT2_write_enable;
@@ -6035,6 +6041,18 @@ sisfb_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		sisfb_detect_custom_timing(ivideo);
 	}
 
+#ifdef CONFIG_FB_SIS_315
+	if (ivideo->chip == XGI_20) {
+		/* Check if our Z7 chip is actually Z9 */
+		SiS_SetRegOR(SISCR, 0x4a, 0x40);	/* GPIOG EN */
+		reg = SiS_GetReg(SISCR, 0x48);
+		if (reg & 0x02) {			/* GPIOG */
+			ivideo->chip_real_id = XGI_21;
+			dev_info(&pdev->dev, "Z9 detected\n");
+		}
+	}
+#endif
+
 	/* POST card in case this has not been done by the BIOS */
 	if( (!ivideo->sisvga_enabled)
 #if !defined(__i386__) && !defined(__x86_64__)

drivers/video/sis/vgatypes.h

@@ -87,6 +87,7 @@ typedef enum _SIS_CHIP_TYPE {
     SIS_341,
     SIS_342,
     XGI_20  = 75,
+    XGI_21,
     XGI_40,
     MAX_SIS_CHIP
 } SIS_CHIP_TYPE;