[PATCH 07/16] drm/amdgpu: add helper to create doorbell pages
Alex Deucher
alexdeucher at gmail.com
Thu Mar 30 20:35:01 UTC 2023
On Thu, Mar 30, 2023 at 11:21 AM Shashank Sharma
<shashank.sharma at amd.com> wrote:
>
>
> On 30/03/2023 16:55, Alex Deucher wrote:
> > On Thu, Mar 30, 2023 at 10:34 AM Shashank Sharma
> > <shashank.sharma at amd.com> wrote:
> >>
> >> 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 <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. :-)
> >> 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.
> > I find the new API confusing. I would expect to see
> > amdgpu_bo_create_kernel(...DOORBELL...), amdgpu_bo_reserve(),
> > amdgpu_bo_kmap(), etc. That makes it consistent with the other
> > resource pools that we manage in ttm.
>
> I am assuming here you are talking about why do we need
> amdgpu_doorbell_page_create()/free() API here.
>
> The wrappers here allow us to do additional book keeping work.
>
> For example:
>
> - We need to validate kernel doorbell writes, which means we need the
> range of kernel doorbells.
>
> - There are 3 kernel doorbell pages, for KGD, KFD and MES. These are non
> consecutive pages.
>
> - While we do doorbell_write in kernel, we need to check if this index
> is correct, which means:
>
> kgd_doobrell_min < index < kgd_doorbell_max
>
> kfd_doobrell_min < index < kgd_doorbell_max
>
> mes_doobrell_min < index < kgd_doorbell_max
>
> - which means we need start/end limits set at every object.
>
> - we have to either do this work at each place where we want to call
> amdgpu_bo_create(DOORBELL)
>
> which means KFD, KGD and MES all places (which will look irrelevant
> in the context)
>
> or we can do this in one place, which is the doorbell wrapper API.
>
>
> Please see patch 10 for this range check.
I don't think we need the range checks for anything other than the
KGD. The MES stuff should just use the same allocation as KGD. KFD
has their own mapping in kfd_doorbell.c and they don't use the
WDOORBELL[64] macros.
Alex
>
>
> - Shashank
>
>
> now kfd is setting start/end limits by calling
> amdgpu_get_doorbell_index() function.
>
> >
> > Alex
> >
> >> - 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.
> >>>>>> */
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