Add support for DRI2 SwapBuffers request

Support the new DRI2 SwapBuffers request with a KMS-specific page flip ioctl.
Doesn't help prevent tearing from CopyRegion requests, but full buffer swaps
look nice.

There's still an open issue with buffer resize in here somewhere; maybe
pI830->front_buffer isn't getting fully fixed up at swap time?

4 files changed, 185 insertions, 6 deletions

diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index 814743b3..e590a2f7 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -30,6 +30,7 @@
 #endif
 
 #include <errno.h>
+#include <poll.h>
 
 #include "xorgVersion.h"
 
@@ -343,6 +344,7 @@ static PixmapPtr
 drmmode_crtc_shadow_create(xf86CrtcPtr crtc, void *data, int width, int height)
 {
 	ScrnInfoPtr pScrn = crtc->scrn;
+	I830Ptr     pI830 = I830PTR(pScrn);
 	drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
 	drmmode_ptr drmmode = drmmode_crtc->drmmode;
 	unsigned long rotate_pitch;
@@ -375,12 +377,16 @@ drmmode_crtc_shadow_create(xf86CrtcPtr crtc, void *data, int width, int height)
 	if (drmmode_crtc->rotate_bo)
 		i830_set_pixmap_bo(rotate_pixmap, drmmode_crtc->rotate_bo);
 
+	pI830->shadow_present = TRUE;
+
 	return rotate_pixmap;
 }
 
 static void
 drmmode_crtc_shadow_destroy(xf86CrtcPtr crtc, PixmapPtr rotate_pixmap, void *data)
 {
+	ScrnInfoPtr pScrn = crtc->scrn;
+	I830Ptr     pI830 = I830PTR(pScrn);
 	drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
 	drmmode_ptr drmmode = drmmode_crtc->drmmode;
 
@@ -398,6 +404,7 @@ drmmode_crtc_shadow_destroy(xf86CrtcPtr crtc, PixmapPtr rotate_pixmap, void *dat
 		dri_bo_unreference(drmmode_crtc->rotate_bo);
 		drmmode_crtc->rotate_bo = NULL;
 	}
+	pI830->shadow_present = FALSE;
 }
 
 static void
@@ -1085,6 +1092,88 @@ drmmode_xf86crtc_resize (ScrnInfoPtr scrn, int width, int height)
 	return FALSE;
 }
 
+Bool
+drmmode_do_pageflip(DrawablePtr pDraw, dri_bo *new_front, dri_bo *old_front)
+{
+    ScreenPtr pScreen = pDraw->pScreen;
+    ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];
+    I830Ptr pI830 = I830PTR(pScrn);
+    xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(pScrn);
+    drmmode_crtc_private_ptr drmmode_crtc = config->crtc[0]->driver_private;
+    drmmode_ptr drmmode = drmmode_crtc->drmmode;
+    unsigned int pitch = pScrn->displayWidth * pI830->cpp;
+    int i, old_fb_id;
+    unsigned int crtc_id;
+    struct pollfd drmpoll;
+    drmEventContext handler = { .page_flip_handler = NULL };
+
+    /*
+     * Create a new handle for the back buffer
+     */
+    old_fb_id = drmmode->fb_id;
+    if (drmModeAddFB(drmmode->fd, pScrn->virtualX, pScrn->virtualY,
+		     pScrn->depth, pScrn->bitsPerPixel, pitch,
+		     new_front->handle, &drmmode->fb_id))
+	    goto error_out;
+
+    /*
+     * Queue flips on all enabled CRTCs
+     * Note that if/when we get per-CRTC buffers, we'll have to update this.
+     * Right now it assumes a single shared fb across all CRTCs, with the
+     * kernel fixing up the offset of each CRTC as necessary.
+     *
+     * Also, flips queued on disabled or incorrectly configured displays
+     * may never complete; this is a configuration error.
+     */
+    for (i = 0; i < config->num_crtc; i++) {
+	    xf86CrtcPtr crtc = config->crtc[i];
+
+	    if (!crtc->enabled)
+		    continue;
+
+	    drmmode_crtc = crtc->driver_private;
+	    crtc_id = drmmode_crtc->mode_crtc->crtc_id;
+	    if (drmModePageFlip(drmmode->fd, crtc_id, drmmode->fb_id, NULL)) {
+		    xf86DrvMsg(pScrn->scrnIndex, X_WARNING,
+			       "flip queue failed: %s\n", strerror(errno));
+		    goto error_undo;
+	    }
+    }
+
+retry:
+    drmpoll.fd = drmmode->fd;
+    drmpoll.events = POLLIN;
+    if (poll(&drmpoll, 1, -1) < 0) {
+	    if (errno == EINTR)
+		    goto retry;
+	    xf86DrvMsg(pScrn->scrnIndex, X_WARNING, "poll failed: %s\n",
+		       strerror(errno));
+	    goto error_undo;
+    }
+
+    drmHandleEvent(drmmode->fd, &handler);
+
+    dri_bo_pin(new_front, 0);
+    dri_bo_unpin(new_front);
+
+    pScrn->fbOffset = new_front->offset;
+    pI830->front_buffer->bo = new_front;
+    pI830->front_buffer->offset = new_front->offset;
+
+    drmModeRmFB(drmmode->fd, old_fb_id);
+
+    return TRUE;
+
+error_undo:
+    drmModeRmFB(drmmode->fd, drmmode->fb_id);
+    drmmode->fb_id = old_fb_id;
+
+error_out:
+    xf86DrvMsg(pScrn->scrnIndex, X_WARNING, "Page flip failed: %s\n",
+	       strerror(errno));
+    return FALSE;
+}
+
 static const xf86CrtcConfigFuncsRec drmmode_xf86crtc_config_funcs = {
 	drmmode_xf86crtc_resize
 };
@@ -1092,8 +1181,10 @@ static const xf86CrtcConfigFuncsRec drmmode_xf86crtc_config_funcs = {
 Bool drmmode_pre_init(ScrnInfoPtr pScrn, int fd, int cpp)
 {
 	xf86CrtcConfigPtr   xf86_config;
+	I830Ptr pI830 = I830PTR(pScrn);
 	drmmode_ptr drmmode;
-	int i;
+	unsigned int i, bad_crtc = 0;
+	int ret;
 
 	drmmode = xnfalloc(sizeof *drmmode);
 	drmmode->fd = fd;
@@ -1120,6 +1211,14 @@ Bool drmmode_pre_init(ScrnInfoPtr pScrn, int fd, int cpp)
 
 	xf86InitialConfiguration(pScrn, TRUE);
 
+	/* Check for swapbuffers support */
+	ret = drmModePageFlip(drmmode->fd, bad_crtc, 1, NULL);
+	if (ret < 0 && errno == ENOENT) { /* bad CRTC or FB number */
+		xf86DrvMsg(pScrn->scrnIndex, X_INFO,
+			   "Kernel page flipping support detected, enabling\n");
+		pI830->use_swap_buffers = TRUE;
+	}
+
 	return TRUE;
 }
 
diff --git a/src/i830.h b/src/i830.h
index 58afe76a..d868c04e 100644
--- a/src/i830.h
+++ b/src/i830.h
@@ -65,6 +65,7 @@ SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include "sarea.h"
 #define _XF86DRI_SERVER_
 #include "dri.h"
+#include "dri2.h"
 #include "GL/glxint.h"
 #include "i830_dri.h"
 #include "intel_bufmgr.h"
@@ -395,6 +396,7 @@ typedef struct _I830Rec {
 #endif
 
    XF86ModReqInfo shadowReq; /* to test for later libshadow */
+   Bool shadow_present;
    Rotation rotation;
    void (*PointerMoved)(int, int, int);
    CreateScreenResourcesProcPtr    CreateScreenResources;
@@ -496,6 +498,8 @@ typedef struct _I830Rec {
    int drmSubFD;
    char deviceName[64];
 
+   Bool use_swap_buffers;
+
    /* Broken-out options. */
    OptionInfoPtr Options;
 
@@ -691,6 +695,8 @@ void I830DRI2CloseScreen(ScreenPtr pScreen);
 extern Bool drmmode_pre_init(ScrnInfoPtr pScrn, int fd, int cpp);
 extern int drmmode_get_pipe_from_crtc_id(drm_intel_bufmgr *bufmgr, xf86CrtcPtr crtc);
 extern int drmmode_output_dpms_status(xf86OutputPtr output);
+extern Bool drmmode_do_pageflip(DrawablePtr pDraw, dri_bo *new_front,
+				dri_bo *old_front);
 
 extern Bool i830_crtc_on(xf86CrtcPtr crtc);
 extern int i830_crtc_to_pipe(xf86CrtcPtr crtc);
diff --git a/src/i830_dri.c b/src/i830_dri.c
index 40d11e4c..0f38d097 100644
--- a/src/i830_dri.c
+++ b/src/i830_dri.c
@@ -45,6 +45,8 @@ USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <errno.h>
 #include <unistd.h>
 #include <fcntl.h>
+#include <sys/time.h>
+#include <time.h>
 
 #include "xf86.h"
 #include "xf86_OSproc.h"
@@ -73,11 +75,6 @@ USE OR OTHER DEALINGS IN THE SOFTWARE.
 extern XF86ModuleData dri2ModuleData;
 #endif
 
-typedef struct {
-    PixmapPtr pPixmap;
-    unsigned int attachment;
-} I830DRI2BufferPrivateRec, *I830DRI2BufferPrivatePtr;
-
 #ifndef USE_DRI2_1_1_0
 static DRI2BufferPtr
 I830DRI2CreateBuffers(DrawablePtr pDraw, unsigned int *attachments, int count)
@@ -359,6 +356,70 @@ I830DRI2CopyRegion(DrawablePtr pDraw, RegionPtr pRegion,
 
 }
 
+#if DRI2INFOREC_VERSION >= 4
+/* Check various flip constraints (drawable parameters vs screen params) */
+static Bool
+i830_flip_ok(DrawablePtr pDraw)
+{
+    ScreenPtr pScreen = pDraw->pScreen;
+    ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];
+    I830Ptr pI830 = I830PTR(pScrn);
+
+    if (pI830->shadow_present)
+	return FALSE;
+    if (pDraw->width != pScrn->virtualX)
+	return FALSE;
+    if (pDraw->height != pScrn->virtualY)
+	return FALSE;
+    if (pDraw->depth != pScrn->depth)
+	return FALSE;
+
+    return TRUE;
+}
+
+/*
+ * DRI2SwapBuffers should try to do a buffer swap if possible, however:
+ *   - if we're swapping buffers smaller than the screen, we have to blit
+ *   - if the back buffer doesn't match the screen depth, we have to blit
+ *   - otherwise we try to swap, and return to the caller the new front
+ *     and back buffers
+ */
+static Bool
+I830DRI2SwapBuffers(DrawablePtr pDraw, DRI2BufferPtr front, DRI2BufferPtr back)
+{
+    ScreenPtr pScreen = pDraw->pScreen;
+    I830DRI2BufferPrivatePtr front_priv, back_priv;
+    dri_bo *tmp_bo;
+    int tmp;
+
+    front_priv = front->driverPrivate;
+    back_priv = back->driverPrivate;
+
+    if (!i830_flip_ok(pDraw))
+	return FALSE;
+
+    /* Swap BO names so DRI works */
+    tmp = front->name;
+    front->name = back->name;
+    back->name = tmp;
+
+    /* Swap pixmap bos */
+    dri_bo_reference(i830_get_pixmap_bo(front_priv->pPixmap));
+
+    tmp_bo = i830_get_pixmap_bo(front_priv->pPixmap);
+    i830_set_pixmap_bo(front_priv->pPixmap,
+		       i830_get_pixmap_bo(back_priv->pPixmap));
+    i830_set_pixmap_bo(back_priv->pPixmap, tmp_bo); /* should be screen */
+
+    if (front_priv->pPixmap != pScreen->GetScreenPixmap(pScreen))
+	FatalError("swapbuffers with bad front\n");
+
+    /* Page flip the full screen buffer */
+    return drmmode_do_pageflip(pDraw, i830_get_pixmap_bo(front_priv->pPixmap),
+			       i830_get_pixmap_bo(back_priv->pPixmap));
+}
+#endif
+
 Bool I830DRI2ScreenInit(ScreenPtr pScreen)
 {
     ScrnInfoPtr pScrn = xf86Screens[pScreen->myNum];
@@ -428,6 +489,13 @@ Bool I830DRI2ScreenInit(ScreenPtr pScreen)
 # endif
 #endif
 
+#if DRI2INFOREC_VERSION >= 4
+    if (pI830->use_swap_buffers) {
+	info.version = 4;
+	info.SwapBuffers = I830DRI2SwapBuffers;
+    }
+#endif
+
     info.CopyRegion = I830DRI2CopyRegion;
 
     return DRI2ScreenInit(pScreen, &info);
diff --git a/src/i830_dri.h b/src/i830_dri.h
index bedbcbe2..e35e9402 100644
--- a/src/i830_dri.h
+++ b/src/i830_dri.h
@@ -2,6 +2,7 @@
 #ifndef _I830_DRI_H
 #define _I830_DRI_H
 
+#include "xorg-server.h"
 #include "xf86drm.h"
 #include "i830_common.h"
 
@@ -58,4 +59,9 @@ typedef struct {
    int dummy;
 } I830DRIContextRec, *I830DRIContextPtr;
 
+typedef struct {
+    PixmapPtr pPixmap;
+    unsigned int attachment;
+} I830DRI2BufferPrivateRec, *I830DRI2BufferPrivatePtr;
+
 #endif