FW: [PATCH v2 2/2] drm/amdgpu: Move to gtt before cpu accesses dma buf.

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For the record.


On 2017-12-13 01:26 PM, Christian König wrote:
> Actually we try to avoid that drivers define their own dma_buf_ops in DRM.
> 
> That's why you have all those callbacks in drm_driver which just mirror the dma_buf interface but unpack the GEM object from the dma-buf object.
> 
> There are quite a number of exceptions, but those drivers then implement everything on their own because the DRM marshaling doesn't make sense for them.
> 
> Christian.
> 
> Am 13.12.2017 um 19:01 schrieb Samuel Li:
>> That is an approach. The cost is to add a new call back, which is not necessary though, since driver can always actually define their own dma_buf_ops.
>> The intention here is to allow a driver reuse drm_gem_prime_dmabuf_ops{}. If you would like to go this far, maybe a more straight forward way is to export those ops, e.g. drm_gem_map_attach, so that a driver can use them in its own definitions.
>>
>> Sam
>>
>>
>>
>> On 2017-12-13 05:23 AM, Christian König wrote:
>>> Something like the attached patch. Not even compile tested.
>>>
>>> Christian.
>>>
>>> Am 12.12.2017 um 20:13 schrieb Samuel Li:
>>>> Not sure if I understand your comments correctly. Currently amdgpu prime reuses drm_gem_prime_dmabuf_ops{}, and it is defined as static which is reasonable. I do not see an easier way to introduce amdgpu_gem_begin_cpu_access().
>>>>
>>>> Sam
>>>>
>>>> On 2017-12-12 01:30 PM, Christian König wrote:
>>>>>> +    while (amdgpu_dmabuf_ops.begin_cpu_access != amdgpu_gem_begin_cpu_access)
>>>>> I would rather just add the four liner code to drm to forward the begin_cpu_access callback into a drm_driver callback instead of all this.
>>>>>
>>>>> But apart from that it looks good to me.
>>>>>
>>>>> Christian.
>>>>>
>>>>> Am 12.12.2017 um 19:14 schrieb Li, Samuel:
>>>>>> A gentle ping on this one, Christian, can you take a look at this?
>>>>>>
>>>>>> Sam
>>>>>>
>>>>>> -----Original Message-----
>>>>>> From: Li, Samuel
>>>>>> Sent: Friday, December 08, 2017 5:22 PM
>>>>>> To: amd-gfx at lists.freedesktop.org
>>>>>> Cc: Li, Samuel <Samuel.Li at amd.com>
>>>>>> Subject: [PATCH v2 2/2] drm/amdgpu: Move to gtt before cpu accesses dma buf.
>>>>>>
>>>>>> To improve cpu read performance. This is implemented for APUs currently.
>>>>>>
>>>>>> v2: Adapt to change https://lists.freedesktop.org/archives/amd-gfx/2017-October/015174.html
>>>>>>
>>>>>> Change-Id: I7a583e23a9ee706e0edd2a46f4e4186a609368e3
>>>>>> ---
>>>>>>     drivers/gpu/drm/amd/amdgpu/amdgpu.h       |  2 ++
>>>>>>     drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c   |  2 +-
>>>>>>     drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c | 58 +++++++++++++++++++++++++++++++
>>>>>>     3 files changed, 61 insertions(+), 1 deletion(-)
>>>>>>
>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>>> index f8657c3..193db70 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
>>>>>> @@ -417,6 +417,8 @@ amdgpu_gem_prime_import_sg_table(struct drm_device *dev,  struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>>>>>>                         struct drm_gem_object *gobj,
>>>>>>                         int flags);
>>>>>> +struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
>>>>>> +                        struct dma_buf *dma_buf);
>>>>>>     int amdgpu_gem_prime_pin(struct drm_gem_object *obj);  void amdgpu_gem_prime_unpin(struct drm_gem_object *obj);  struct reservation_object *amdgpu_gem_prime_res_obj(struct drm_gem_object *); diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>>> index 31383e0..df30b08 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c
>>>>>> @@ -868,7 +868,7 @@ static struct drm_driver kms_driver = {
>>>>>>         .prime_handle_to_fd = drm_gem_prime_handle_to_fd,
>>>>>>         .prime_fd_to_handle = drm_gem_prime_fd_to_handle,
>>>>>>         .gem_prime_export = amdgpu_gem_prime_export,
>>>>>> -    .gem_prime_import = drm_gem_prime_import,
>>>>>> +    .gem_prime_import = amdgpu_gem_prime_import,
>>>>>>         .gem_prime_pin = amdgpu_gem_prime_pin,
>>>>>>         .gem_prime_unpin = amdgpu_gem_prime_unpin,
>>>>>>         .gem_prime_res_obj = amdgpu_gem_prime_res_obj, diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>>> index ae9c106..de6f599 100644
>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_prime.c
>>>>>> @@ -26,6 +26,7 @@
>>>>>>     #include <drm/drmP.h>
>>>>>>       #include "amdgpu.h"
>>>>>> +#include "amdgpu_display.h"
>>>>>>     #include <drm/amdgpu_drm.h>
>>>>>>     #include <linux/dma-buf.h>
>>>>>>     @@ -164,6 +165,33 @@ struct reservation_object *amdgpu_gem_prime_res_obj(struct drm_gem_object *obj)
>>>>>>         return bo->tbo.resv;
>>>>>>     }
>>>>>>     +static int amdgpu_gem_begin_cpu_access(struct dma_buf *dma_buf, enum
>>>>>> +dma_data_direction direction) {
>>>>>> +    struct amdgpu_bo *bo = gem_to_amdgpu_bo(dma_buf->priv);
>>>>>> +    struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
>>>>>> +    struct ttm_operation_ctx ctx = { true, false };
>>>>>> +    u32 domain = amdgpu_framebuffer_domains(adev);
>>>>>> +    long ret = 0;
>>>>>> +    bool reads = (direction == DMA_BIDIRECTIONAL || direction ==
>>>>>> +DMA_FROM_DEVICE);
>>>>>> +
>>>>>> +    if (!reads || !(domain | AMDGPU_GEM_DOMAIN_GTT) || bo->pin_count)
>>>>>> +        return 0;
>>>>>> +
>>>>>> +    /* move to gtt */
>>>>>> +    ret = amdgpu_bo_reserve(bo, false);
>>>>>> +    if (unlikely(ret != 0))
>>>>>> +        return ret;
>>>>>> +
>>>>>> +    amdgpu_ttm_placement_from_domain(bo, AMDGPU_GEM_DOMAIN_GTT);
>>>>>> +    ret = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
>>>>>> +
>>>>>> +    amdgpu_bo_unreserve(bo);
>>>>>> +    return ret;
>>>>>> +}
>>>>>> +
>>>>>> +static struct dma_buf_ops amdgpu_dmabuf_ops; static atomic_t aops_lock;
>>>>>> +
>>>>>>     struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>>>>>>                         struct drm_gem_object *gobj,
>>>>>>                         int flags)
>>>>>> @@ -178,5 +206,35 @@ struct dma_buf *amdgpu_gem_prime_export(struct drm_device *dev,
>>>>>>         buf = drm_gem_prime_export(dev, gobj, flags);
>>>>>>         if (!IS_ERR(buf))
>>>>>>             buf->file->f_mapping = dev->anon_inode->i_mapping;
>>>>>> +
>>>>>> +    while (amdgpu_dmabuf_ops.begin_cpu_access != amdgpu_gem_begin_cpu_access)
>>>>>> +    {
>>>>>> +        if (!atomic_cmpxchg(&aops_lock, 0, 1)) {
>>>>>> +            amdgpu_dmabuf_ops = *(buf->ops);
>>>>>> +            amdgpu_dmabuf_ops.begin_cpu_access = amdgpu_gem_begin_cpu_access;
>>>>>> +        }
>>>>>> +    }
>>>>>> +    buf->ops = &amdgpu_dmabuf_ops;
>>>>>> +
>>>>>>         return buf;
>>>>>>     }
>>>>>> +
>>>>>> +struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
>>>>>> +                        struct dma_buf *dma_buf)
>>>>>> +{
>>>>>> +    struct drm_gem_object *obj;
>>>>>> +
>>>>>> +    if (dma_buf->ops == &amdgpu_dmabuf_ops) {
>>>>>> +        obj = dma_buf->priv;
>>>>>> +        if (obj->dev == dev) {
>>>>>> +            /*
>>>>>> +             * Importing dmabuf exported from out own gem increases
>>>>>> +             * refcount on gem itself instead of f_count of dmabuf.
>>>>>> +             */
>>>>>> +            drm_gem_object_get(obj);
>>>>>> +            return obj;
>>>>>> +        }
>>>>>> +    }
>>>>>> +
>>>>>> +    return drm_gem_prime_import(dev, dma_buf); }
>>>>>> -- 
>>>>>> 2.7.4
>>>>>>
> 
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