drm/mgag200: Rewrite cursor handling

The cursor handling in mgag200 is complicated to understand. It touches a
number of different BOs, but doesn't really use all of them.

Rewriting the cursor update reduces the amount of cursor state. There are
two BOs for double-buffered HW updates. The source BO updates the one that
is currently not displayed and then switches buffers. Explicit BO locking
has been removed from the code. BOs are simply pinned and unpinned in video
RAM.

v2:
	* pin cursor BOs to current location
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190613073041.29350-8-tzimmermann@suse.de

drivers/gpu/drm/mgag200/mgag200_cursor.c

@@ -22,10 +22,9 @@ static void mga_hide_cursor(struct mga_device *mdev)
 {
 	WREG8(MGA_CURPOSXL, 0);
 	WREG8(MGA_CURPOSXH, 0);
-	if (mdev->cursor.pixels_1->pin_count)
-		drm_gem_vram_unpin_locked(mdev->cursor.pixels_1);
-	if (mdev->cursor.pixels_2->pin_count)
-		drm_gem_vram_unpin_locked(mdev->cursor.pixels_2);
+	if (mdev->cursor.pixels_current)
+		drm_gem_vram_unpin(mdev->cursor.pixels_current);
+	mdev->cursor.pixels_current = NULL;
 }
 
 int mga_crtc_cursor_set(struct drm_crtc *crtc,
@@ -39,7 +38,7 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 	struct drm_gem_vram_object *pixels_1 = mdev->cursor.pixels_1;
 	struct drm_gem_vram_object *pixels_2 = mdev->cursor.pixels_2;
 	struct drm_gem_vram_object *pixels_current = mdev->cursor.pixels_current;
-	struct drm_gem_vram_object *pixels_prev = mdev->cursor.pixels_prev;
+	struct drm_gem_vram_object *pixels_next;
 	struct drm_gem_object *obj;
 	struct drm_gem_vram_object *gbo = NULL;
 	int ret = 0;
@@ -52,6 +51,7 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 	bool found = false;
 	int colour_count = 0;
 	s64 gpu_addr;
+	u64 dst_gpu;
 	u8 reg_index;
 	u8 this_row[48];
 
@@ -61,80 +61,66 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 		return -ENOTSUPP; /* Didn't allocate space for cursors */
 	}
 
-	if ((width != 64 || height != 64) && handle) {
-		WREG8(MGA_CURPOSXL, 0);
-		WREG8(MGA_CURPOSXH, 0);
-		return -EINVAL;
+	if (WARN_ON(pixels_current &&
+		    pixels_1 != pixels_current &&
+		    pixels_2 != pixels_current)) {
+		return -ENOTSUPP; /* inconsistent state */
 	}
 
-	BUG_ON(pixels_1 != pixels_current && pixels_1 != pixels_prev);
-	BUG_ON(pixels_2 != pixels_current && pixels_2 != pixels_prev);
-	BUG_ON(pixels_current == pixels_prev);
-
 	if (!handle || !file_priv) {
 		mga_hide_cursor(mdev);
 		return 0;
 	}
 
-	obj = drm_gem_object_lookup(file_priv, handle);
-	if (!obj)
-		return -ENOENT;
-
-	ret = drm_gem_vram_lock(pixels_1, true);
-	if (ret) {
+	if (width != 64 || height != 64) {
 		WREG8(MGA_CURPOSXL, 0);
 		WREG8(MGA_CURPOSXH, 0);
-		goto out_unref;
-	}
-	ret = drm_gem_vram_lock(pixels_2, true);
-	if (ret) {
-		WREG8(MGA_CURPOSXL, 0);
-		WREG8(MGA_CURPOSXH, 0);
-		drm_gem_vram_unlock(pixels_1);
-		goto out_unlock1;
+		return -EINVAL;
 	}
 
-	/* Move cursor buffers into VRAM if they aren't already */
-	if (!pixels_1->pin_count) {
-		ret = drm_gem_vram_pin_locked(pixels_1,
-					      DRM_GEM_VRAM_PL_FLAG_VRAM);
-		if (ret)
-			goto out1;
-		gpu_addr = drm_gem_vram_offset(pixels_1);
-		if (gpu_addr < 0) {
-			drm_gem_vram_unpin_locked(pixels_1);
-			goto out1;
-		}
-		mdev->cursor.pixels_1_gpu_addr = gpu_addr;
-	}
-	if (!pixels_2->pin_count) {
-		ret = drm_gem_vram_pin_locked(pixels_2,
-					      DRM_GEM_VRAM_PL_FLAG_VRAM);
-		if (ret) {
-			drm_gem_vram_unpin_locked(pixels_1);
-			goto out1;
-		}
-		gpu_addr = drm_gem_vram_offset(pixels_2);
-		if (gpu_addr < 0) {
-			drm_gem_vram_unpin_locked(pixels_1);
-			drm_gem_vram_unpin_locked(pixels_2);
-			goto out1;
-		}
-		mdev->cursor.pixels_2_gpu_addr = gpu_addr;
-	}
+	if (pixels_current == pixels_1)
+		pixels_next = pixels_2;
+	else
+		pixels_next = pixels_1;
 
+	obj = drm_gem_object_lookup(file_priv, handle);
+	if (!obj)
+		return -ENOENT;
 	gbo = drm_gem_vram_of_gem(obj);
-	ret = drm_gem_vram_lock(gbo, true);
+	ret = drm_gem_vram_pin(gbo, 0);
 	if (ret) {
 		dev_err(&dev->pdev->dev, "failed to lock user bo\n");
-		goto out1;
+		goto err_drm_gem_object_put_unlocked;
 	}
 	src = drm_gem_vram_kmap(gbo, true, NULL);
 	if (IS_ERR(src)) {
 		ret = PTR_ERR(src);
-		dev_err(&dev->pdev->dev, "failed to kmap user buffer updates\n");
-		goto out2;
+		dev_err(&dev->pdev->dev,
+			"failed to kmap user buffer updates\n");
+		goto err_drm_gem_vram_unpin_src;
+	}
+
+	/* Pin and map up-coming buffer to write colour indices */
+	ret = drm_gem_vram_pin(pixels_next, 0);
+	if (ret)
+		dev_err(&dev->pdev->dev,
+			"failed to pin cursor buffer: %d\n", ret);
+		goto err_drm_gem_vram_kunmap_src;
+	dst = drm_gem_vram_kmap(pixels_next, true, NULL);
+	if (IS_ERR(dst)) {
+		ret = PTR_ERR(dst);
+		dev_err(&dev->pdev->dev,
+			"failed to kmap cursor updates: %d\n", ret);
+		goto err_drm_gem_vram_unpin_dst;
+	}
+	gpu_addr = drm_gem_vram_offset(pixels_2);
+	if (gpu_addr < 0) {
+		ret = (int)gpu_addr;
+		dev_err(&dev->pdev->dev,
+			"failed to get cursor scanout address: %d\n", ret);
+		goto err_drm_gem_vram_kunmap_dst;
 	}
+	dst_gpu = (u64)gpu_addr;
 
 	memset(&colour_set[0], 0, sizeof(uint32_t)*16);
 	/* width*height*4 = 16384 */
@@ -149,7 +135,7 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 				warn_transparent = false; /* Only tell the user once. */
 			}
 			ret = -EINVAL;
-			goto out3;
+			goto err_drm_gem_vram_kunmap_dst;
 		}
 		/* Don't need to store transparent pixels as colours */
 		if (this_colour>>24 == 0x0)
@@ -171,7 +157,7 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 				warn_palette = false; /* Only tell the user once. */
 			}
 			ret = -EINVAL;
-			goto out3;
+			goto err_drm_gem_vram_kunmap_dst;
 		}
 		*next_space = this_colour;
 		next_space++;
@@ -190,14 +176,6 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 		BUG_ON((colour_set[i]>>24 & 0xff) != 0xff);
 	}
 
-	/* Map up-coming buffer to write colour indices */
-	dst = drm_gem_vram_kmap(pixels_prev, true, NULL);
-	if (IS_ERR(dst)) {
-		ret = PTR_ERR(dst);
-		dev_err(&dev->pdev->dev, "failed to kmap cursor updates\n");
-		goto out3;
-	}
-
 	/* now write colour indices into hardware cursor buffer */
 	for (row = 0; row < 64; row++) {
 		memset(&this_row[0], 0, 48);
@@ -224,42 +202,35 @@ int mga_crtc_cursor_set(struct drm_crtc *crtc,
 	}
 
 	/* Program gpu address of cursor buffer */
-	if (pixels_prev == pixels_1)
-		gpu_addr = mdev->cursor.pixels_1_gpu_addr;
-	else
-		gpu_addr = mdev->cursor.pixels_2_gpu_addr;
-	WREG_DAC(MGA1064_CURSOR_BASE_ADR_LOW, (u8)((gpu_addr>>10) & 0xff));
-	WREG_DAC(MGA1064_CURSOR_BASE_ADR_HI, (u8)((gpu_addr>>18) & 0x3f));
+	WREG_DAC(MGA1064_CURSOR_BASE_ADR_LOW, (u8)((dst_gpu>>10) & 0xff));
+	WREG_DAC(MGA1064_CURSOR_BASE_ADR_HI, (u8)((dst_gpu>>18) & 0x3f));
 
 	/* Adjust cursor control register to turn on the cursor */
 	WREG_DAC(MGA1064_CURSOR_CTL, 4); /* 16-colour palletized cursor mode */
 
-	/* Now swap internal buffer pointers */
-	if (mdev->cursor.pixels_1 == mdev->cursor.pixels_prev) {
-		mdev->cursor.pixels_prev = mdev->cursor.pixels_2;
-		mdev->cursor.pixels_current = mdev->cursor.pixels_1;
-	} else if (mdev->cursor.pixels_1 == mdev->cursor.pixels_current) {
-		mdev->cursor.pixels_prev = mdev->cursor.pixels_1;
-		mdev->cursor.pixels_current = mdev->cursor.pixels_2;
-	} else {
-		BUG();
-	}
-	ret = 0;
+	/* Now update internal buffer pointers */
+	if (pixels_current)
+		drm_gem_vram_unpin(pixels_current);
+	mdev->cursor.pixels_current = pixels_next;
 
-	drm_gem_vram_kunmap(pixels_prev);
- out3:
+	drm_gem_vram_kunmap(pixels_next);
+	drm_gem_vram_unpin(pixels_next);
 	drm_gem_vram_kunmap(gbo);
- out2:
-	drm_gem_vram_unlock(gbo);
- out1:
-	if (ret)
-		mga_hide_cursor(mdev);
-	drm_gem_vram_unlock(pixels_1);
-out_unlock1:
-	drm_gem_vram_unlock(pixels_2);
-out_unref:
+	drm_gem_vram_unpin(gbo);
 	drm_gem_object_put_unlocked(obj);
 
+	return 0;
+
+err_drm_gem_vram_kunmap_dst:
+	drm_gem_vram_kunmap(pixels_next);
+err_drm_gem_vram_unpin_dst:
+	drm_gem_vram_unpin(pixels_next);
+err_drm_gem_vram_kunmap_src:
+	drm_gem_vram_kunmap(gbo);
+err_drm_gem_vram_unpin_src:
+	drm_gem_vram_unpin(gbo);
+err_drm_gem_object_put_unlocked:
+	drm_gem_object_put_unlocked(obj);
 	return ret;
 }
 

drivers/gpu/drm/mgag200/mgag200_drv.h

@@ -158,11 +158,8 @@ struct mga_cursor {
 	*/
 	struct drm_gem_vram_object *pixels_1;
 	struct drm_gem_vram_object *pixels_2;
-	u64 pixels_1_gpu_addr, pixels_2_gpu_addr;
 	/* The currently displayed icon, this points to one of pixels_1, or pixels_2 */
 	struct drm_gem_vram_object *pixels_current;
-	/* The previously displayed icon */
-	struct drm_gem_vram_object *pixels_prev;
 };
 
 struct mga_mc {

drivers/gpu/drm/mgag200/mgag200_main.c

@@ -241,10 +241,8 @@ int mgag200_driver_load(struct drm_device *dev, unsigned long flags)
 		mdev->cursor.pixels_2 = NULL;
 		dev_warn(&dev->pdev->dev,
 			"Could not allocate space for cursors. Not doing hardware cursors.\n");
-	} else {
-		mdev->cursor.pixels_current = mdev->cursor.pixels_1;
-		mdev->cursor.pixels_prev = mdev->cursor.pixels_2;
 	}
+	mdev->cursor.pixels_current = NULL;
 
 	return 0;