Re: [PATCH 07/16] drm/amdgpu: add helper to create doorbell pages

[Shashank Sharma]

On 30/03/2023 16:15, Luben Tuikov wrote:

On 2023-03-30 10:04, Shashank Sharma wrote:

On 30/03/2023 15:42, Luben Tuikov wrote:

On 2023-03-29 11:47, Shashank Sharma wrote:

From: Shashank Sharma <contactshashanksha...@gmail.com>

This patch adds helper functions to create and free doorbell
pages for kernel objects.

Cc: Alex Deucher <alexander.deuc...@amd.com>
Cc: Christian Koenig <christian.koe...@amd.com>
Signed-off-by: Shashank Sharma <shashank.sha...@amd.com>
---
   drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell.h  | 41 ++++++++++++++++
   .../gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c  | 49 +++++++++++++++++++
   2 files changed, 90 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell.h 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell.h
index f9c3b77bf65d..6581b78fe438 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell.h
@@ -27,6 +27,24 @@
   /*
    * GPU doorbell structures, functions & helpers
    */
+
+/* Structure to hold doorbell pages from PCI doorbell BAR */
+struct amdgpu_doorbell_obj {

In the comment you say "Structure to hold ...";
it is a C structure, but then in the name of a function we see "obj".
(Object is something which is defined like in memory, i.e. it exists, not
something which is only declared.)
This is just a declaration of a structure, not an object per se.
I'd call it "struct amdgpu_doorbell_struct" or just "struct amdgpu_doorbell".

It is similar to struct amdgpu buffer object (struct amdgpu_bo), and
many more existing structure.

The amdpgu_bo is very different than a structure describing a doorbell.
The doorbell description isn't really "an object". I understand
the enthusiasm, but it is really not "an object". It's just a doorbell
description. :-)

amdgpu_bo is page of ttm_memory with additional information,

amdgpu_doorbell_obj is a page of ttm_doorbells with additional information

(it is not just one doorbell description)

I don't see a problem here.

- Shashank

Regards,
Luben

- Shashank

Then in the definition, you can call it an object/objects, if you'd like,
like "struct amdgpu_doorbell *doorb_object[];" then you can say
"db = doorb_object[i]";

Regards,
Luben

+       struct amdgpu_bo *bo;
+       uint64_t gpu_addr;
+       uint32_t *cpu_addr;
+       uint32_t size;
+
+       /* First index in this object */
+       uint32_t start;
+
+       /* Last index in this object */
+       uint32_t end;
+
+       /* bitmap for dynamic doorbell allocation from this object */
+       unsigned long *doorbell_bitmap;
+};
+
   struct amdgpu_doorbell {
        /* doorbell mmio */
        resource_size_t         base;
@@ -328,6 +346,29 @@ int amdgpu_device_doorbell_init(struct amdgpu_device 
*adev);
    */
   void amdgpu_device_doorbell_fini(struct amdgpu_device *adev);

+/**

+ * amdgpu_doorbell_free_page - Free a doorbell page
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * @db_age: previously allocated doobell page details
+ *
+ */
+void amdgpu_doorbell_free_page(struct amdgpu_device *adev,
+                               struct amdgpu_doorbell_obj *db_obj);
+
+/**
+ * amdgpu_doorbell_alloc_page - create a page from doorbell pool
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * @db_age: doobell page structure to fill details with
+ *
+ * returns 0 on success, else error number
+ */
+int amdgpu_doorbell_alloc_page(struct amdgpu_device *adev,
+                               struct amdgpu_doorbell_obj *db_obj);
+
   #define RDOORBELL32(index) amdgpu_mm_rdoorbell(adev, (index))
   #define WDOORBELL32(index, v) amdgpu_mm_wdoorbell(adev, (index), (v))
   #define RDOORBELL64(index) amdgpu_mm_rdoorbell64(adev, (index))
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c
index 1aea92363fd3..8be15b82b545 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c
@@ -111,6 +111,55 @@ void amdgpu_mm_wdoorbell64(struct amdgpu_device *adev, u32 
index, u64 v)
        }
   }

+/**

+ * amdgpu_doorbell_free_page - Free a doorbell page
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * @db_age: previously allocated doobell page details
+ *
+ */
+void amdgpu_doorbell_free_page(struct amdgpu_device *adev,
+                                       struct amdgpu_doorbell_obj *db_obj)
+{
+       amdgpu_bo_free_kernel(&db_obj->bo,
+                             &db_obj->gpu_addr,
+                             (void **)&db_obj->cpu_addr);
+
+}
+
+/**
+ * amdgpu_doorbell_alloc_page - create a page from doorbell pool
+ *
+ * @adev: amdgpu_device pointer
+ *
+ * @db_age: doobell page structure to fill details with
+ *
+ * returns 0 on success, else error number
+ */
+int amdgpu_doorbell_alloc_page(struct amdgpu_device *adev,
+                               struct amdgpu_doorbell_obj *db_obj)
+{
+       int r;
+
+       db_obj->size = ALIGN(db_obj->size, PAGE_SIZE);
+
+       r = amdgpu_bo_create_kernel(adev,
+                                   db_obj->size,
+                                   PAGE_SIZE,
+                                   AMDGPU_GEM_DOMAIN_DOORBELL,
+                                   &db_obj->bo,
+                                   &db_obj->gpu_addr,
+                                   (void **)&db_obj->cpu_addr);
+
+       if (r) {
+               DRM_ERROR("Failed to create doorbell BO, err=%d\n", r);
+               return r;
+       }
+
+       return 0;
+}
+
   /*
    * GPU doorbell aperture helpers function.
    */