DRI2: Added new "SwapbuffersWait" option for xorg.conf

When enabled, it tries to avoid tearing in OpenGL ES applications.
Works on sunxi hardware in the case if the hardware overlay (sunxi
disp layer) is used for a DRI2 window. The name of this option and
the description in the man page has been borrowed from intel and
radeon drivers.
Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>

man/sunxifb.man

@@ -104,6 +104,15 @@ some improvements are possible in this area. But if you really care
 about the desktop performance, then you likely don't want to enable
 any compositing effects in your window manager anyway.
 .TP
+.BI "Option \*qSwapbuffersWait\*q \*q" boolean \*q
+This option controls the behavior of eglSwapBuffers calls by OpenGL ES
+applications. If enabled, the calls will try to avoid tearing by making
+sure the display scanline is outside of the area to be copied before the
+copy occurs. If disabled, no scanline synchronization is performed,
+meaning tearing will likely occur. Note that when enabled, this option
+can adversely affect the framerate of applications that render frames
+at less than refresh rate.  Default: enabled.
+.TP
 .BI "Option \*qAccelMethod\*q \*q" "string" \*q
 Chooses between available acceleration architectures. Valid values are
 .B G2D

src/fbdev.c

@@ -167,6 +167,7 @@ typedef enum {
 	OPTION_SW_CURSOR,
 	OPTION_DRI2,
 	OPTION_DRI2_OVERLAY,
+	OPTION_SWAPBUFFERS_WAIT,
 	OPTION_ACCELMETHOD,
 	OPTION_USE_BS,
 	OPTION_FORCE_BS,
@@ -182,6 +183,7 @@ static const OptionInfoRec FBDevOptions[] = {
 	{ OPTION_SW_CURSOR,	"SWCursor",	OPTV_BOOLEAN,	{0},	FALSE },
 	{ OPTION_DRI2,		"DRI2",		OPTV_BOOLEAN,	{0},	FALSE },
 	{ OPTION_DRI2_OVERLAY,	"DRI2HWOverlay",OPTV_BOOLEAN,	{0},	FALSE },
+	{ OPTION_SWAPBUFFERS_WAIT,"SwapbuffersWait",OPTV_BOOLEAN,{0},	FALSE },
 	{ OPTION_ACCELMETHOD,	"AccelMethod",	OPTV_STRING,	{0},	FALSE },
 	{ OPTION_USE_BS,	"UseBackingStore",OPTV_BOOLEAN,	{0},	FALSE },
 	{ OPTION_FORCE_BS,	"ForceBackingStore",OPTV_BOOLEAN,{0},	FALSE },
@@ -1047,7 +1049,8 @@ FBDevScreenInit(SCREEN_INIT_ARGS_DECL)
 	if (xf86ReturnOptValBool(fPtr->Options, OPTION_DRI2, TRUE)) {
 
 	    fPtr->SunxiMaliDRI2_private = SunxiMaliDRI2_Init(pScreen,
-		xf86ReturnOptValBool(fPtr->Options, OPTION_DRI2_OVERLAY, TRUE));
+		xf86ReturnOptValBool(fPtr->Options, OPTION_DRI2_OVERLAY, TRUE),
+		xf86ReturnOptValBool(fPtr->Options, OPTION_SWAPBUFFERS_WAIT, TRUE));
 
 	    if (fPtr->SunxiMaliDRI2_private) {
 		xf86DrvMsg(pScrn->scrnIndex, X_INFO,

src/sunxi_mali_ump_dri2.c

@@ -614,6 +614,11 @@ static void MaliDRI2CopyRegion(DrawablePtr   pDraw,
     sunxi_layer_set_x8r8g8b8_input_buffer(disp, umpbuf->offs, umpbuf->width,
                                           umpbuf->height, umpbuf->pitch / 4);
     sunxi_layer_show(disp);
+
+    if (drvpriv->bSwapbuffersWait) {
+        /* FIXME: blocking here for up to 1/60 second is not nice */
+        sunxi_wait_for_vsync(disp);
+    }
 }
 
 /************************************************************************/
@@ -838,7 +843,9 @@ static void DisableHWCursor(ScrnInfoPtr pScrn)
     }
 }
 
-SunxiMaliDRI2 *SunxiMaliDRI2_Init(ScreenPtr pScreen, Bool bUseOverlay)
+SunxiMaliDRI2 *SunxiMaliDRI2_Init(ScreenPtr pScreen,
+                                  Bool      bUseOverlay,
+                                  Bool      bSwapbuffersWait)
 {
     int drm_fd;
     DRI2InfoRec info;
@@ -909,6 +916,9 @@ SunxiMaliDRI2 *SunxiMaliDRI2_Init(ScreenPtr pScreen, Bool bUseOverlay)
         xf86DrvMsg(pScreen->myNum, X_INFO,
               "display controller hardware overlays are not used for DRI2\n");
 
+    xf86DrvMsg(pScreen->myNum, X_INFO, "Wait on SwapBuffers? %s\n",
+               bSwapbuffersWait ? "enabled" : "disabled");
+
     info.version = 3;
 
     info.driverName = "sunxi-mali";
@@ -949,6 +959,7 @@ SunxiMaliDRI2 *SunxiMaliDRI2_Init(ScreenPtr pScreen, Bool bUseOverlay)
         }
 
         private->drm_fd = drm_fd;
+        private->bSwapbuffersWait = bSwapbuffersWait;
         return private;
     }
 }

src/sunxi_mali_ump_dri2.h

@@ -131,9 +131,14 @@ typedef struct {
     DRI2WindowStatePtr      HashWindowState;
 
     int                     drm_fd;
+
+    /* Wait for vsync when swapping DRI2 buffers */
+    Bool                    bSwapbuffersWait;
 } SunxiMaliDRI2;
 
-SunxiMaliDRI2 *SunxiMaliDRI2_Init(ScreenPtr pScreen, Bool bUseOverlay);
+SunxiMaliDRI2 *SunxiMaliDRI2_Init(ScreenPtr pScreen,
+                                  Bool      bUseOverlay,
+                                  Bool      bSwapbuffersWait);
 void SunxiMaliDRI2_Close(ScreenPtr pScreen);
 
 #endif

xorg.conf

@@ -12,4 +12,6 @@ Section "Device"
         Identifier      "Allwinner A10/A13 FBDEV"
         Driver          "sunxifb"
         Option          "fbdev" "/dev/fb0"
+
+        Option          "SwapbuffersWait" "true"
 EndSection