intel: Make the option to control VSync and PageFlip explict

Too often our implementation of vsync or pageflip is buggy, or for some
other reason it is desired by the user to disable those code paths. Make
it possible once again by restoring the Options for the user to control.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

7 files changed, 60 insertions, 12 deletions

diff --git a/man/intel.man b/man/intel.man
index 0a265114..cd217b1a 100644
--- a/man/intel.man
+++ b/man/intel.man
@@ -196,13 +196,31 @@ i.e. perform synchronous rendering.
 Default: Disabled
 .TP
 .TP
+.BI "Option \*qVSync\*q \*q" boolean \*q
+This option controls the use of commands to synchronise rendering with the
+vertical refresh of the display. Some rendering commands have the option
+to be performed in a "tear-free" fashion by stalling the GPU to wait for
+the display to be outside of the region to be updated. This slows down all
+rendering, and historically has been the source of many GPU hangs.
+.IP
+Default: enabled.
+.TP
+.BI "Option \*qPageFlip\*q \*q" boolean \*q
+This option controls the use of commands to flip the scanout address on a
+VBlank. This is used by glXSwapBuffers to efficiently perform the back-to-front
+exchange at the end of a frame without incurring the penalty of a copy, or
+stalling the render pipeline (the flip is performed asynchronrously to the
+render command stream by the display engine). However, it has historically
+been the source of many GPU hangs.
+.IP
+Default: enabled.
+.TP
 .BI "Option \*qSwapbuffersWait\*q \*q" boolean \*q
 This option controls the behavior of glXSwapBuffers and glXCopySubBufferMESA
 calls by GL applications.  If enabled, the calls will 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.
+will likely occur.
 .IP
 Default: enabled.
 .TP
diff --git a/src/intel_options.c b/src/intel_options.c
index 153cc629..6d53a3f3 100644
--- a/src/intel_options.c
+++ b/src/intel_options.c
@@ -13,6 +13,8 @@ const OptionInfoRec intel_options[] = {
 	{OPTION_VIDEO_KEY,	"VideoKey",	OPTV_INTEGER,	{0},	0},
 	{OPTION_TILING_2D,	"Tiling",	OPTV_BOOLEAN,	{0},	1},
 	{OPTION_TILING_FB,	"LinearFramebuffer",	OPTV_BOOLEAN,	{0},	0},
+	{OPTION_VSYNC, "VSync", OPTV_BOOLEAN,	{0},	1},
+	{OPTION_PAGEFLIP, "PageFlip", OPTV_BOOLEAN,	{0},	1},
 	{OPTION_SWAPBUFFERS_WAIT, "SwapbuffersWait", OPTV_BOOLEAN,	{0},	1},
 	{OPTION_TRIPLE_BUFFER,	"TripleBuffer", OPTV_BOOLEAN,	{0},	1},
 	{OPTION_PREFER_OVERLAY, "XvPreferOverlay", OPTV_BOOLEAN, {0}, 0},
diff --git a/src/intel_options.h b/src/intel_options.h
index 095660c3..e61075b3 100644
--- a/src/intel_options.h
+++ b/src/intel_options.h
@@ -19,6 +19,8 @@ enum intel_options {
 	OPTION_COLOR_KEY,
 	OPTION_TILING_2D,
 	OPTION_TILING_FB,
+	OPTION_VSYNC,
+	OPTION_PAGEFLIP,
 	OPTION_SWAPBUFFERS_WAIT,
 	OPTION_TRIPLE_BUFFER,
 	OPTION_PREFER_OVERLAY,
diff --git a/src/sna/sna.h b/src/sna/sna.h
index 2f732eb1..32d9ef37 100644
--- a/src/sna/sna.h
+++ b/src/sna/sna.h
@@ -226,7 +226,8 @@ struct sna {
 	unsigned flags;
 #define SNA_NO_WAIT		0x1
 #define SNA_NO_FLIP		0x2
-#define SNA_TRIPLE_BUFFER	0x4
+#define SNA_NO_VSYNC		0x4
+#define SNA_TRIPLE_BUFFER	0x8
 #define SNA_TEAR_FREE		0x10
 #define SNA_FORCE_SHADOW	0x20
 #define SNA_FLUSH_GTT		0x40
diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
index 1d1022e0..f1482341 100644
--- a/src/sna/sna_display.c
+++ b/src/sna/sna_display.c
@@ -3627,6 +3627,9 @@ sna_wait_for_scanline(struct sna *sna,
 	assert(to_sna_crtc(crtc)->bo != NULL);
 	assert(pixmap == sna->front);
 
+	if (sna->flags & SNA_NO_VSYNC)
+		return false;
+
 	/*
 	 * Make sure we don't wait for a scanline that will
 	 * never occur
diff --git a/src/sna/sna_dri.c b/src/sna/sna_dri.c
index 25f66b31..4c5476e4 100644
--- a/src/sna/sna_dri.c
+++ b/src/sna/sna_dri.c
@@ -303,7 +303,7 @@ sna_dri_create_buffer(DrawablePtr draw,
 	case DRI2BufferBackLeft:
 		if (draw->width  == sna->front->drawable.width &&
 		    draw->height == sna->front->drawable.height &&
-		    (sna->flags & SNA_NO_FLIP) == 0)
+		    (sna->flags & (SNA_NO_WAIT | SNA_NO_FLIP)) == 0)
 			flags |= CREATE_SCANOUT;
 	case DRI2BufferBackRight:
 	case DRI2BufferFrontRight:
@@ -1080,6 +1080,8 @@ can_flip(struct sna * sna,
 	WindowPtr win = (WindowPtr)draw;
 	PixmapPtr pixmap;
 
+	assert((sna->flags & SNA_NO_WAIT) == 0);
+
 	if (draw->type == DRAWABLE_PIXMAP)
 		return false;
 
@@ -1967,7 +1969,9 @@ sna_dri_schedule_swap(ClientPtr client, DrawablePtr draw, DRI2BufferPtr front,
 	assert(sna_pixmap_from_drawable(draw)->flush);
 
 	/* Drawable not displayed... just complete the swap */
-	pipe = sna_dri_get_pipe(draw);
+	pipe = -1;
+	if (sna->flags & SNA_NO_WAIT)
+		pipe = sna_dri_get_pipe(draw);
 	if (pipe == -1) {
 		DBG(("%s: off-screen, immediate update\n", __FUNCTION__));
 		goto blit;
diff --git a/src/sna/sna_driver.c b/src/sna/sna_driver.c
index 4da6cbb0..da5740a7 100644
--- a/src/sna/sna_driver.c
+++ b/src/sna/sna_driver.c
@@ -294,12 +294,20 @@ static void sna_selftest(void)
 	sna_damage_selftest();
 }
 
+static bool has_vsync(struct sna *sna)
+{
+	if (sna->flags & SNA_IS_HOSTED)
+		return false;
+
+	return true;
+}
+
 static bool has_pageflipping(struct sna *sna)
 {
 	drm_i915_getparam_t gp;
 	int v;
 
-	if (sna->flags & (SNA_IS_HOSTED | SNA_NO_WAIT))
+	if (sna->flags & SNA_IS_HOSTED)
 		return false;
 
 	v = 0;
@@ -508,13 +516,23 @@ static Bool sna_pre_init(ScrnInfoPtr scrn, int flags)
 
 	if (!xf86ReturnOptValBool(sna->Options, OPTION_SWAPBUFFERS_WAIT, TRUE))
 		sna->flags |= SNA_NO_WAIT;
-	if (xf86ReturnOptValBool(sna->Options, OPTION_TRIPLE_BUFFER, TRUE))
-		sna->flags |= SNA_TRIPLE_BUFFER;
-	if (has_pageflipping(sna)) {
-		if (xf86ReturnOptValBool(sna->Options, OPTION_TEAR_FREE, FALSE))
-			sna->flags |= SNA_TEAR_FREE;
-	} else
+
+	if (!has_vsync(sna) ||
+	    !xf86ReturnOptValBool(sna->Options, OPTION_VSYNC, TRUE))
+		sna->flags |= SNA_NO_VSYNC;
+
+	if (!has_pageflipping(sna) ||
+	    !xf86ReturnOptValBool(sna->Options, OPTION_PAGEFLIP, TRUE))
 		sna->flags |= SNA_NO_FLIP;
+
+	if ((sna->flags & (SNA_NO_VSYNC | SNA_NO_FLIP | SNA_NO_WAIT)) == 0 &&
+	    xf86ReturnOptValBool(sna->Options, OPTION_TRIPLE_BUFFER, TRUE))
+		sna->flags |= SNA_TRIPLE_BUFFER;
+
+	if ((sna->flags & (SNA_NO_VSYNC | SNA_NO_FLIP)) == 0 &&
+	    xf86ReturnOptValBool(sna->Options, OPTION_TEAR_FREE, FALSE))
+		sna->flags |= SNA_TEAR_FREE;
+
 	if (xf86ReturnOptValBool(sna->Options, OPTION_CRTC_PIXMAPS, FALSE))
 		sna->flags |= SNA_FORCE_SHADOW;