Fix VGA plane disabling

Only apply on G4X with SR01 bit5 workaround for VGA plane disable, and
restore behavior back for other chips to make sure other modes got disabled
too.

For bug #17235, #19715, #21064, #23178

Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

1 files changed, 20 insertions, 18 deletions

diff --git a/src/i830_display.c b/src/i830_display.c
index 59ededcf..f83e0212 100644
--- a/src/i830_display.c
+++ b/src/i830_display.c
@@ -1076,29 +1076,31 @@ i830_disable_vga_plane (xf86CrtcPtr crtc)
 {
     ScrnInfoPtr pScrn = crtc->scrn;
     I830Ptr pI830 = I830PTR(pScrn);
-    uint32_t vgacntrl = INREG(VGACNTRL);
     uint8_t sr01;
 
-    if (vgacntrl & VGA_DISP_DISABLE)
-        return;
-
     /*
-       Set bit 5 of SR01;
-       Wait 30us;
-       */
-    OUTREG8(SRX, 1);
-    sr01 = INREG8(SRX + 1);
-    OUTREG8(SRX + 1, sr01 | (1 << 5));
-    usleep(30);
-    /* disable center mode on 965GM and G4X platform */
-    if (IS_I965GM(pI830) || IS_G4X(pI830))
-        vgacntrl &= ~(3 << 24);
-
-    vgacntrl |= VGA_DISP_DISABLE;
-
-    OUTREG(VGACNTRL, vgacntrl);
+     * Bug #17235: G4X machine needs following steps
+     * for disable VGA.
+     * - set bit 5 of SR01;
+     * - Wait 30us;
+     * - disable vga plane;
+     * - restore SR01;
+     */
+    if (IS_G4X(pI830)) {
+        OUTREG8(SRX, 1);
+        sr01 = INREG8(SRX + 1);
+        OUTREG8(SRX + 1, sr01 | (1 << 5));
+        usleep(30);
+    }
+
+    OUTREG(VGACNTRL, VGA_DISP_DISABLE);
     i830WaitForVblank(pScrn);
 
+    /* restore SR01 */
+    if (IS_G4X(pI830)) {
+        OUTREG8(SRX, 1);
+        OUTREG8(SRX + 1, sr01);
+    }
 }
 
 static void