drm/amdgpu: create kernel doorbell pages

This patch:
- creates a doorbell page for graphics driver usages.
- adds a few new varlables in adev->doorbell structure to
  keep track of kernel's doorbell-bo.
- removes the adev->doorbell.ptr variable, replaces it with
  kernel-doorbell-bo's cpu address.

V2: - Create doorbell BO directly, no wrappe functions (Alex)
    - no additional doorbell structure (Alex, Christian)
    - Use doorbell_cpu_ptr, remove ioremap (Christian, Alex)
    - Allocate one extra page of doorbells for MES (Alex)

V4: Move MES doorbell base init into MES related patch (Christian)

Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Christian Koenig <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Shashank Sharma <shashank.sharma@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell.h

@@ -31,10 +31,15 @@ struct amdgpu_doorbell {
 	/* doorbell mmio */
 	resource_size_t		base;
 	resource_size_t		size;
-	u32 __iomem		*ptr;
 
 	/* Number of doorbells reserved for amdgpu kernel driver */
 	u32 num_kernel_doorbells;
+
+	/* Kernel doorbells */
+	struct amdgpu_bo *kernel_doorbells;
+
+	/* For CPU access of doorbells */
+	uint32_t *cpu_addr;
 };
 
 /* Reserved doorbells for amdgpu (including multimedia).
@@ -350,6 +355,7 @@ void amdgpu_mm_wdoorbell64(struct amdgpu_device *adev, u32 index, u64 v);
  */
 int amdgpu_doorbell_init(struct amdgpu_device *adev);
 void amdgpu_doorbell_fini(struct amdgpu_device *adev);
+int amdgpu_doorbell_create_kernel_doorbells(struct amdgpu_device *adev);
 
 #define RDOORBELL32(index) amdgpu_mm_rdoorbell(adev, (index))
 #define WDOORBELL32(index, v) amdgpu_mm_wdoorbell(adev, (index), (v))