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

[Luben Tuikov]

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 <contactshashanksharma at gmail.com>
>>>
>>> This patch adds helper functions to create and free doorbell
>>> pages for kernel objects.
>>>
>>> Cc: Alex Deucher <alexander.deucher at amd.com>
>>> Cc: Christian Koenig <christian.koenig at amd.com>
>>> Signed-off-by: Shashank Sharma <shashank.sharma at 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. :-)

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.
>>>    */