Move struct amdgpu_wb and helpers out of the monolithic header amdgpu.h
into its own dedicated header amdgpu_wb.h.

Move functions amdgpu_device_wb_get() and amdgpu_device_wb_free out of
amdgpu_device.c into new dedicated amdgpu_wb.c file.

Update amdgpu/Makefile to build amdgpu_wb.o.

This is part of the ongoing effort to reduce the size of amdgpu.h into
their own respective separate headers.

Signed-off-by: Shahyan Soltani <[email protected]>
---
 drivers/gpu/drm/amd/amdgpu/Makefile        |   3 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu.h        |  68 +-------------
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c |  45 ----------
 drivers/gpu/drm/amd/amdgpu/amdgpu_wb.c     |  69 ++++++++++++++
 drivers/gpu/drm/amd/amdgpu/amdgpu_wb.h     | 100 +++++++++++++++++++++
 5 files changed, 172 insertions(+), 113 deletions(-)
 create mode 100644 drivers/gpu/drm/amd/amdgpu/amdgpu_wb.c
 create mode 100644 drivers/gpu/drm/amd/amdgpu/amdgpu_wb.h

diff --git a/drivers/gpu/drm/amd/amdgpu/Makefile 
b/drivers/gpu/drm/amd/amdgpu/Makefile
index ee3574797bc2..e6deb24f73bb 100644
--- a/drivers/gpu/drm/amd/amdgpu/Makefile
+++ b/drivers/gpu/drm/amd/amdgpu/Makefile
@@ -71,7 +71,8 @@ amdgpu-y += amdgpu_device.o amdgpu_reg_access.o 
amdgpu_doorbell_mgr.o amdgpu_kms
        amdgpu_fw_attestation.o amdgpu_securedisplay.o \
        amdgpu_eeprom.o amdgpu_mca.o amdgpu_psp_ta.o amdgpu_lsdma.o \
        amdgpu_ring_mux.o amdgpu_xcp.o amdgpu_seq64.o amdgpu_aca.o 
amdgpu_dev_coredump.o \
-       amdgpu_cper.o amdgpu_userq_fence.o amdgpu_eviction_fence.o amdgpu_ip.o
+       amdgpu_cper.o amdgpu_userq_fence.o amdgpu_eviction_fence.o amdgpu_ip.o \
+       amdgpu_wb.o
 
 amdgpu-$(CONFIG_PROC_FS) += amdgpu_fdinfo.o
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index d7d8664854fd..9a714b4b59bc 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -112,6 +112,7 @@
 #include "amdgpu_userq.h"
 #include "amdgpu_eviction_fence.h"
 #include "amdgpu_sa.h"
+#include "amdgpu_wb.h"
 #include "amdgpu_ip.h"
 #if defined(CONFIG_DRM_AMD_ISP)
 #include "amdgpu_isp.h"
@@ -429,73 +430,6 @@ struct amdgpu_fpriv {
 
 int amdgpu_file_to_fpriv(struct file *filp, struct amdgpu_fpriv **fpriv);
 
-/*
- * Writeback
- */
-#define AMDGPU_MAX_WB 1024     /* Reserve at most 1024 WB slots for 
amdgpu-owned rings. */
-
-/**
- * struct amdgpu_wb - This struct is used for small GPU memory allocation.
- *
- * This struct is used to allocate a small amount of GPU memory that can be
- * used to shadow certain states into the memory. This is especially useful for
- * providing easy CPU access to some states without requiring register access
- * (e.g., if some block is power gated, reading register may be problematic).
- *
- * Note: the term writeback was initially used because many of the amdgpu
- * components had some level of writeback memory, and this struct initially
- * described those components.
- */
-struct amdgpu_wb {
-
-       /**
-        * @wb_obj:
-        *
-        * Buffer Object used for the writeback memory.
-        */
-       struct amdgpu_bo        *wb_obj;
-
-       /**
-        * @wb:
-        *
-        * Pointer to the first writeback slot. In terms of CPU address
-        * this value can be accessed directly by using the offset as an index.
-        * For the GPU address, it is necessary to use gpu_addr and the offset.
-        */
-       uint32_t                *wb;
-
-       /**
-        * @gpu_addr:
-        *
-        * Writeback base address in the GPU.
-        */
-       uint64_t                gpu_addr;
-
-       /**
-        * @num_wb:
-        *
-        * Number of writeback slots reserved for amdgpu.
-        */
-       u32                     num_wb;
-
-       /**
-        * @used:
-        *
-        * Track the writeback slot already used.
-        */
-       unsigned long           used[DIV_ROUND_UP(AMDGPU_MAX_WB, 
BITS_PER_LONG)];
-
-       /**
-        * @lock:
-        *
-        * Protects read and write of the used field array.
-        */
-       spinlock_t              lock;
-};
-
-int amdgpu_device_wb_get(struct amdgpu_device *adev, u32 *wb);
-void amdgpu_device_wb_free(struct amdgpu_device *adev, u32 wb);
-
 /*
  * Benchmarking
  */
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 5ff224163bab..15a6a9010fc8 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -1058,51 +1058,6 @@ static int amdgpu_device_wb_init(struct amdgpu_device 
*adev)
        return 0;
 }
 
-/**
- * amdgpu_device_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_device_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_device_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_device_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);
-}
-
 /**
  * amdgpu_device_resize_fb_bar - try to resize FB BAR
  *
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..8e5f572077f3
--- /dev/null
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.c
@@ -0,0 +1,69 @@
+// 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 "amdgpu.h"
+#include "amdgpu_wb.h"
+#include <linux/spinlock.h>
+/**
+ * amdgpu_device_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_device_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_device_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_device_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);
+}
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.h
new file mode 100644
index 000000000000..dac9fc3f0004
--- /dev/null
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_wb.h
@@ -0,0 +1,100 @@
+/* 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.
+ */
+#ifndef __AMDGPU_WB_H__
+#define __AMDGPU_WB_H__
+
+#include <linux/types.h>
+#include <linux/spinlock_types.h>
+#include <linux/math.h>
+
+/*
+ * Writeback
+ */
+#define AMDGPU_MAX_WB 1024     /* Reserve at most 1024 WB slots for 
amdgpu-owned rings. */
+
+/**
+ * struct amdgpu_wb - This struct is used for small GPU memory allocation.
+ *
+ * This struct is used to allocate a small amount of GPU memory that can be
+ * used to shadow certain states into the memory. This is especially useful for
+ * providing easy CPU access to some states without requiring register access
+ * (e.g., if some block is power gated, reading register may be problematic).
+ *
+ * Note: the term writeback was initially used because many of the amdgpu
+ * components had some level of writeback memory, and this struct initially
+ * described those components.
+ */
+
+struct amdgpu_bo;
+struct amdgpu_device;
+
+struct amdgpu_wb {
+
+       /**
+        * @wb_obj:
+        *
+        * Buffer Object used for the writeback memory.
+        */
+       struct amdgpu_bo        *wb_obj;
+
+       /**
+        * @wb:
+        *
+        * Pointer to the first writeback slot. In terms of CPU address
+        * this value can be accessed directly by using the offset as an index.
+        * For the GPU address, it is necessary to use gpu_addr and the offset.
+        */
+       uint32_t                *wb;
+
+       /**
+        * @gpu_addr:
+        *
+        * Writeback base address in the GPU.
+        */
+       uint64_t                gpu_addr;
+
+       /**
+        * @num_wb:
+        *
+        * Number of writeback slots reserved for amdgpu.
+        */
+       u32                     num_wb;
+
+       /**
+        * @used:
+        *
+        * Track the writeback slot already used.
+        */
+       unsigned long           used[DIV_ROUND_UP(AMDGPU_MAX_WB, 
BITS_PER_LONG)];
+
+       /**
+        * @lock:
+        *
+        * Protects read and write of the used field array.
+        */
+       spinlock_t              lock;
+};
+
+int amdgpu_device_wb_get(struct amdgpu_device *adev, u32 *wb);
+void amdgpu_device_wb_free(struct amdgpu_device *adev, u32 wb);
+#endif
-- 
2.54.0

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