1 files changed, 129 insertions, 0 deletions
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.c
new file mode 100644
index 000000000000..8b7061c94ccd
--- /dev/null
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.c
@@ -0,0 +1,129 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright 2026 Advanced Micro Devices, Inc.
+
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
+ * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <linux/spinlock.h>
+
+#include "amdgpu.h"
+#include "amdgpu_wb.h"
+
+/*
+ * amdgpu_wb_*()
+ * Writeback is the method by which the GPU updates special pages in memory
+ * with the status of certain GPU events (fences, ring pointers,etc.).
+ */
+
+/**
+ * amdgpu_wb_fini - Disable Writeback and free memory
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * Disables Writeback and frees the Writeback memory (all asics).
+ * Used at driver shutdown.
+ */
+void amdgpu_wb_fini(struct amdgpu_device *adev)
+{
+	if (adev->wb.wb_obj) {
+		amdgpu_bo_free_kernel(&adev->wb.wb_obj,
+				      &adev->wb.gpu_addr,
+				      (void **)&adev->wb.wb);
+		adev->wb.wb_obj = NULL;
+	}
+}
+
+/**
+ * amdgpu_wb_init - Init Writeback driver info and allocate memory
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * Initializes writeback and allocates writeback memory (all asics).
+ * Used at driver startup.
+ * Returns 0 on success or an -error on failure.
+ */
+int amdgpu_wb_init(struct amdgpu_device *adev)
+{
+	int r;
+
+	if (adev->wb.wb_obj == NULL) {
+		/* AMDGPU_MAX_WB * sizeof(uint32_t) * 8 = AMDGPU_MAX_WB 256bit slots */
+		r = amdgpu_bo_create_kernel(adev, AMDGPU_MAX_WB * sizeof(uint32_t) * 8,
+					    PAGE_SIZE, AMDGPU_GEM_DOMAIN_GTT,
+					    &adev->wb.wb_obj, &adev->wb.gpu_addr,
+					    (void **)&adev->wb.wb);
+		if (r) {
+			dev_warn(adev->dev, "(%d) create WB bo failed\n", r);
+			return r;
+		}
+
+		adev->wb.num_wb = AMDGPU_MAX_WB;
+		memset(&adev->wb.used, 0, sizeof(adev->wb.used));
+
+		/* clear wb memory */
+		memset((char *)adev->wb.wb, 0, AMDGPU_MAX_WB * sizeof(uint32_t) * 8);
+	}
+
+	return 0;
+}
+
+/**
+ * amdgpu_wb_get - Allocate a wb entry
+ *
+ * @adev: amdgpu_device pointer
+ * @wb: wb index
+ *
+ * Allocate a wb slot for use by the driver (all asics).
+ * Returns 0 on success or -EINVAL on failure.
+ */
+int amdgpu_wb_get(struct amdgpu_device *adev, u32 *wb)
+{
+	unsigned long flags, offset;
+
+	spin_lock_irqsave(&adev->wb.lock, flags);
+	offset = find_first_zero_bit(adev->wb.used, adev->wb.num_wb);
+	if (offset < adev->wb.num_wb) {
+		__set_bit(offset, adev->wb.used);
+		spin_unlock_irqrestore(&adev->wb.lock, flags);
+		*wb = offset << 3; /* convert to dw offset */
+		return 0;
+	} else {
+		spin_unlock_irqrestore(&adev->wb.lock, flags);
+		return -EINVAL;
+	}
+}
+
+/**
+ * amdgpu_wb_free - Free a wb entry
+ *
+ * @adev: amdgpu_device pointer
+ * @wb: wb index
+ *
+ * Free a wb slot allocated for use by the driver (all asics)
+ */
+void amdgpu_wb_free(struct amdgpu_device *adev, u32 wb)
+{
+	unsigned long flags;
+
+	wb >>= 3;
+	spin_lock_irqsave(&adev->wb.lock, flags);
+	if (wb < adev->wb.num_wb)
+		__clear_bit(wb, adev->wb.used);
+	spin_unlock_irqrestore(&adev->wb.lock, flags);
+}