Use two HW cursor buffers per CRTC

Switch to the other buffer when xf86_config->cursor changes. Avoids
these issues possible when re-using the same buffer:

* The HW may intermittently display a mix of the old and new cursor
  images.
* If the hotspot changes, the HW may intermittently display the new
  cursor image at the location corresponding to the old image's hotspot.

Bugzilla: https://bugs.freedesktop.org/108832
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 38 insertions, 16 deletions

diff --git a/src/amdgpu_kms.c b/src/amdgpu_kms.c
index fad2382..4cd46f2 100644
--- a/src/amdgpu_kms.c
+++ b/src/amdgpu_kms.c
@@ -2275,25 +2275,28 @@ static Bool amdgpu_setup_kernel_mem(ScreenPtr pScreen)
 	xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(pScrn);
 	int cpp = info->pixel_bytes;
 	int cursor_size;
-	int c;
+	int c, i;
 
 	cursor_size = info->cursor_w * info->cursor_h * 4;
 	cursor_size = AMDGPU_ALIGN(cursor_size, AMDGPU_GPU_PAGE_SIZE);
 	for (c = 0; c < xf86_config->num_crtc; c++) {
 		drmmode_crtc_private_ptr drmmode_crtc = xf86_config->crtc[c]->driver_private;
 
-		if (!drmmode_crtc->cursor_buffer) {
-			drmmode_crtc->cursor_buffer = amdgpu_bo_open(pAMDGPUEnt->pDev,
-								     cursor_size, 0,
-								     AMDGPU_GEM_DOMAIN_VRAM);
-			if (!(drmmode_crtc->cursor_buffer)) {
-				ErrorF("Failed to allocate cursor buffer memory\n");
-				return FALSE;
-			}
+		for (i = 0; i < 2; i++) {
+			if (!drmmode_crtc->cursor_buffer[i]) {
+				drmmode_crtc->cursor_buffer[i] =
+					amdgpu_bo_open(pAMDGPUEnt->pDev,
+						       cursor_size, 0,
+						       AMDGPU_GEM_DOMAIN_VRAM);
+
+				if (!(drmmode_crtc->cursor_buffer[i])) {
+					ErrorF("Failed to allocate cursor buffer memory\n");
+					return FALSE;
+				}
 
-			if (amdgpu_bo_cpu_map(drmmode_crtc->cursor_buffer->bo.amdgpu,
-					      &drmmode_crtc->cursor_buffer->cpu_ptr)) {
-				ErrorF("Failed to map cursor buffer memory\n");
+				if (amdgpu_bo_cpu_map(drmmode_crtc->cursor_buffer[i]->bo.amdgpu,
+						      &drmmode_crtc->cursor_buffer[i]->cpu_ptr))
+					ErrorF("Failed to map cursor buffer memory\n");
 			}
 		}
 	}
diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index 84d9a48..92cf543 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -1633,17 +1633,24 @@ drmmode_cursor_pixel(xf86CrtcPtr crtc, uint32_t *argb, Bool *premultiplied,
 static void drmmode_load_cursor_argb(xf86CrtcPtr crtc, CARD32 * image)
 {
 	drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
-	uint32_t *ptr = (uint32_t *) (drmmode_crtc->cursor_buffer->cpu_ptr);
 	ScrnInfoPtr pScrn = crtc->scrn;
 	AMDGPUInfoPtr info = AMDGPUPTR(pScrn);
+	unsigned id = drmmode_crtc->cursor_id;
 	Bool premultiplied = TRUE;
 	Bool apply_gamma = TRUE;
 	uint32_t argb;
+	uint32_t *ptr;
 
 	if ((crtc->scrn->depth != 24 && crtc->scrn->depth != 32) ||
 	    drmmode_cm_enabled(&info->drmmode))
 		apply_gamma = FALSE;
 
+	if (drmmode_crtc->cursor &&
+	    XF86_CRTC_CONFIG_PTR(pScrn)->cursor != drmmode_crtc->cursor)
+		id ^= 1;
+
+	ptr = (uint32_t *) (drmmode_crtc->cursor_buffer[id]->cpu_ptr);
+
 #if XF86_CRTC_VERSION < 7
 	if (crtc->driverIsPerformingTransform) {
 		uint32_t cursor_w = info->cursor_w, cursor_h = info->cursor_h;
@@ -1681,6 +1688,11 @@ retry:
 			ptr[i] = cpu_to_le32(argb);
 		}
 	}
+
+	if (id != drmmode_crtc->cursor_id) {
+		drmmode_crtc->cursor_id = id;
+		crtc->funcs->show_cursor(crtc);
+	}
 }
 
 #if XORG_VERSION_CURRENT >= XORG_VERSION_NUMERIC(1,15,99,903,0)
@@ -1705,7 +1717,7 @@ static void drmmode_hide_cursor(xf86CrtcPtr crtc)
 
 	drmModeSetCursor(pAMDGPUEnt->fd, drmmode_crtc->mode_crtc->crtc_id, 0,
 			 info->cursor_w, info->cursor_h);
-
+	drmmode_crtc->cursor = NULL;
 }
 
 static void drmmode_show_cursor(xf86CrtcPtr crtc)
@@ -1714,6 +1726,8 @@ static void drmmode_show_cursor(xf86CrtcPtr crtc)
 	AMDGPUInfoPtr info = AMDGPUPTR(pScrn);
 	AMDGPUEntPtr pAMDGPUEnt = AMDGPUEntPriv(pScrn);
 	drmmode_crtc_private_ptr drmmode_crtc = crtc->driver_private;
+	struct amdgpu_buffer *cursor_buffer =
+		drmmode_crtc->cursor_buffer[drmmode_crtc->cursor_id];
 	xf86CrtcConfigPtr xf86_config = XF86_CRTC_CONFIG_PTR(pScrn);
 	CursorPtr cursor = xf86_config->cursor;
 	int xhot = cursor->bits->xhot;
@@ -1721,9 +1735,11 @@ static void drmmode_show_cursor(xf86CrtcPtr crtc)
 	static Bool use_set_cursor2 = TRUE;
 	struct drm_mode_cursor2 arg;
 
+	drmmode_crtc->cursor = xf86_config->cursor;
+
 	memset(&arg, 0, sizeof(arg));
 
-	if (!amdgpu_bo_get_handle(drmmode_crtc->cursor_buffer, &arg.handle)) {
+	if (!amdgpu_bo_get_handle(cursor_buffer, &arg.handle)) {
 		ErrorF("failed to get BO handle for cursor\n");
 		return;
 	}
diff --git a/src/drmmode_display.h b/src/drmmode_display.h
index 87b301e..2fb97df 100644
--- a/src/drmmode_display.h
+++ b/src/drmmode_display.h
@@ -108,11 +108,14 @@ typedef struct {
 	drmModeCrtcPtr mode_crtc;
 	int hw_id;
 
+	CursorPtr cursor;
 	int cursor_x;
 	int cursor_y;
 	int cursor_xhot;
 	int cursor_yhot;
-	struct amdgpu_buffer *cursor_buffer;
+	unsigned cursor_id;
+	struct amdgpu_buffer *cursor_buffer[2];
+
 	struct drmmode_scanout rotate;
 	struct drmmode_scanout scanout[2];
 	DamagePtr scanout_damage;