Fallback to blitting when out of scanout memory

If DRM can't allocate a scanout buffer for a flippable
window's back buffer, we now attempt to allocate a
non-scanout buffer and blit the window rather than
fail the DRI2 buffer allocation completely.

Note that this fallback is only suitable for back
buffers - if reallocating the front buffer (on
res change etc.) failed, we can't fall back to a
non-scanout buffer.

Change-Id: I9614dde01e80fd3dc03a37afee1a38d00dd55348

4 files changed, 60 insertions, 14 deletions

diff --git a/src/armsoc_dri2.c b/src/armsoc_dri2.c
index a2e71ca..ae8b05e 100644
--- a/src/armsoc_dri2.c
+++ b/src/armsoc_dri2.c
@@ -229,16 +229,16 @@ ARMSOCDRI2CreateBuffer(DrawablePtr pDraw, unsigned int attachment,
 		goto fail;
 	}
 
-	/* Q: how to know across ARMSOC generations what formats the display
-	 *    can support directly?
-	 * A: attempt to create a drm_framebuffer, and if that fails then the
-	 * hw must not support.. then fall back to blitting
-	 */
 	if (canflip(pDraw) && attachment != DRI2BufferFrontLeft) {
+		/* Create an fb around this buffer. This will fail and we will
+		 * fall back to blitting if the display controller hardware
+		 * cannot scan out this buffer (for example, if it doesn't
+		 * support the format or there was insufficient scanout memory
+		 * at buffer creation time). */
 		int ret = armsoc_bo_add_fb(bo);
 		if (ret) {
-			/* to-bad, so-sad, we can't flip */
-			WARNING_MSG("could not create fb: %d", ret);
+			WARNING_MSG(
+					"Falling back to blitting a flippable window");
 		}
 	}
 
diff --git a/src/armsoc_dumb.c b/src/armsoc_dumb.c
index d395b89..a1fd800 100644
--- a/src/armsoc_dumb.c
+++ b/src/armsoc_dumb.c
@@ -350,7 +350,6 @@ int armsoc_bo_add_fb(struct armsoc_bo *bo)
 	ret = drmModeAddFB(bo->dev->fd, bo->width, bo->height, bo->depth,
 			bo->bpp, bo->pitch, bo->handle, &bo->fb_id);
 	if (ret < 0) {
-		xf86DrvMsg(-1, X_ERROR, "Could not add fb to bo %d\n", ret);
 		bo->fb_id = 0;
 		return ret;
 	}
diff --git a/src/armsoc_exa.c b/src/armsoc_exa.c
index 8aaa297..879c605 100644
--- a/src/armsoc_exa.c
+++ b/src/armsoc_exa.c
@@ -96,6 +96,21 @@ ARMSOCCreatePixmap2(ScreenPtr pScreen, int width, int height,
 				height,
 				depth,
 				bitsPerPixel, buf_type);
+
+		if ((!priv->bo) && ARMSOC_BO_SCANOUT == buf_type) {
+			/* Tried to create a scanout but failed. Attempt to
+			 * fall back to non-scanout instead.
+			 */
+			WARNING_MSG(
+					"Scanout buffer allocation failed, falling back to non-scanout");
+			buf_type = ARMSOC_BO_NON_SCANOUT;
+			priv->bo = armsoc_bo_new_with_dim(pARMSOC->dev,
+					width,
+					height,
+					depth,
+					bitsPerPixel, buf_type);
+		}
+
 		if (!priv->bo) {
 			ERROR_MSG("failed to allocate %dx%d bo, buf_type = %d",
 					width, height, buf_type);
@@ -204,6 +219,20 @@ ARMSOCModifyPixmapHeader(PixmapPtr pPixmap, int width, int height,
 				pPixmap->drawable.depth,
 				pPixmap->drawable.bitsPerPixel, buf_type);
 
+		if ((!priv->bo) && ARMSOC_BO_SCANOUT == buf_type) {
+			/* Tried to create a scanout but failed. Attempt to
+			 * fall back to non-scanout instead.
+			 */
+			WARNING_MSG(
+					"Scanout buffer allocation failed, falling back to non-scanout");
+			buf_type = ARMSOC_BO_NON_SCANOUT;
+			priv->bo = armsoc_bo_new_with_dim(pARMSOC->dev,
+					pPixmap->drawable.width,
+					pPixmap->drawable.height,
+					pPixmap->drawable.depth,
+					pPixmap->drawable.bitsPerPixel,
+					buf_type);
+		}
 		if (!priv->bo) {
 			ERROR_MSG("failed to allocate %dx%d bo, buf_type = %d",
 					pPixmap->drawable.width,
diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index f805e29..ba6d439 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -200,8 +200,11 @@ drmmode_set_mode_major(xf86CrtcPtr crtc, DisplayModePtr mode,
 				pScrn->virtualX, pScrn->virtualY);
 
 		ret = armsoc_bo_add_fb(pARMSOC->scanout);
-		if (ret)
+		if (ret) {
+			ERROR_MSG(
+					"Failed to add framebuffer to the scanout buffer");
 			return FALSE;
+		}
 
 		fb_id = armsoc_bo_get_fb(pARMSOC->scanout);
 		if (0 == fb_id)
@@ -1144,24 +1147,39 @@ drmmode_xf86crtc_resize(ScrnInfoPtr pScrn, int width, int height)
 			/* Resize the bo */
 			if (armsoc_bo_resize(pARMSOC->scanout, width, height)) {
 				armsoc_bo_clear(pARMSOC->scanout);
-				armsoc_bo_add_fb(pARMSOC->scanout);
+				if (armsoc_bo_add_fb(pARMSOC->scanout))
+					ERROR_MSG(
+							"Failed to add framebuffer to the existing scanout buffer");
 				return FALSE;
 			}
+
 			/* Add new fb to the bo */
-			if (armsoc_bo_clear(pARMSOC->scanout) ||
-					armsoc_bo_add_fb(pARMSOC->scanout))
+			if (armsoc_bo_clear(pARMSOC->scanout))
+				return FALSE;
+
+			if (armsoc_bo_add_fb(pARMSOC->scanout)) {
+				ERROR_MSG(
+						"Failed to add framebuffer to the existing scanout buffer");
 				return FALSE;
+			}
 
 			pitch = armsoc_bo_pitch(pARMSOC->scanout);
 		} else {
 			DEBUG_MSG("allocated new scanout buffer okay");
 			pitch = armsoc_bo_pitch(new_scanout);
 			/* clear new BO and add FB */
-			if (armsoc_bo_clear(new_scanout) ||
-					armsoc_bo_add_fb(new_scanout)) {
+			if (armsoc_bo_clear(new_scanout)) {
+				armsoc_bo_unreference(new_scanout);
+				return FALSE;
+			}
+
+			if (armsoc_bo_add_fb(new_scanout)) {
+				ERROR_MSG(
+						"Failed to add framebuffer to the new scanout buffer");
 				armsoc_bo_unreference(new_scanout);
 				return FALSE;
 			}
+
 			/* Handle dma_buf fd that may be attached to old bo */
 			if (armsoc_bo_has_dmabuf(pARMSOC->scanout)) {
 				int res;