Re: [PATCH v4 3/8] drm/i915: Add a new "remapped" gtt_view

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 26/10/2018 13:43, Ville Syrjälä wrote:
> On Fri, Oct 26, 2018 at 10:19:25AM +0100, Tvrtko Ursulin wrote:
>>
>> On 23/10/2018 17:02, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>>
>>> To overcome display engine stride limits we'll want to remap the
>>> pages in the GTT. To that end we need a new gtt_view type which
>>> is just like the "rotated" type except not rotated.
>>>
>>> v2: Use intel_remapped_plane_info base type
>>>       s/unused/unused_mbz/ (Chris)
>>>       Separate BUILD_BUG_ON()s (Chris)
>>>       Use I915_GTT_PAGE_SIZE (Chris)
>>> v3: Use i915_gem_object_get_dma_address() (Chris)
>>>       Trim the sg (Tvrtko)
>>>
>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>> Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
>>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> ---
>>>    drivers/gpu/drm/i915/i915_debugfs.c       | 12 ++++
>>>    drivers/gpu/drm/i915/i915_gem_gtt.c       | 74 +++++++++++++++++++++++
>>>    drivers/gpu/drm/i915/i915_gem_gtt.h       | 25 ++++++--
>>>    drivers/gpu/drm/i915/i915_vma.c           |  6 +-
>>>    drivers/gpu/drm/i915/i915_vma.h           |  3 +
>>>    drivers/gpu/drm/i915/intel_display.c      | 11 ++++
>>>    drivers/gpu/drm/i915/intel_drv.h          |  1 +
>>>    drivers/gpu/drm/i915/selftests/i915_vma.c |  6 +-
>>>    8 files changed, 130 insertions(+), 8 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
>>> index 5b37d5f8e132..ce019126304d 100644
>>> --- a/drivers/gpu/drm/i915/i915_debugfs.c
>>> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
>>> @@ -196,6 +196,18 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
>>>    					   vma->ggtt_view.rotated.plane[1].offset);
>>>    				break;
>>>    
>>> +			case I915_GGTT_VIEW_REMAPPED:
>>> +				seq_printf(m, ", remapped [(%ux%u, stride=%u, offset=%u), (%ux%u, stride=%u, offset=%u)]",
>>> +					   vma->ggtt_view.remapped.plane[0].width,
>>> +					   vma->ggtt_view.remapped.plane[0].height,
>>> +					   vma->ggtt_view.remapped.plane[0].stride,
>>> +					   vma->ggtt_view.remapped.plane[0].offset,
>>> +					   vma->ggtt_view.remapped.plane[1].width,
>>> +					   vma->ggtt_view.remapped.plane[1].height,
>>> +					   vma->ggtt_view.remapped.plane[1].stride,
>>> +					   vma->ggtt_view.remapped.plane[1].offset);
>>> +				break;
>>> +
>>>    			default:
>>>    				MISSING_CASE(vma->ggtt_view.type);
>>>    				break;
>>> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
>>> index 98d9a1eb1ed2..d0e50b584ebd 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem_gtt.c
>>> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
>>> @@ -3705,6 +3705,75 @@ intel_rotate_pages(struct intel_rotation_info *rot_info,
>>>    	return ERR_PTR(ret);
>>>    }
>>>    
>>> +static struct scatterlist *
>>> +remap_pages(struct drm_i915_gem_object *obj, unsigned int offset,
>>> +	    unsigned int width, unsigned int height,
>>> +	    unsigned int stride,
>>> +	    struct sg_table *st, struct scatterlist *sg)
>>> +{
>>> +	unsigned int column, row;
>>> +
>>> +	for (row = 0; row < height; row++) {
>>> +		for (column = 0; column < width; column++) {
>>> +			st->nents++;
>>> +			/* We don't need the pages, but need to initialize
>>> +			 * the entries so the sg list can be happily traversed.
>>> +			 * The only thing we need are DMA addresses.
>>> +			 */
>>> +			sg_set_page(sg, NULL, I915_GTT_PAGE_SIZE, 0);
>>> +			sg_dma_address(sg) =
>>> +				i915_gem_object_get_dma_address(obj, offset + column);
>>> +			sg_dma_len(sg) = I915_GTT_PAGE_SIZE;
>>
>> Sg trim will do nothing since the nents is equal to num pages. To
>> benefit from it, you would need to look for consecutive DMA addresses
>> and "append" to the existing sg entry in those cases.
> 
> Hmm. I thought that is what sg_trim() does. I guess not.

Ah.. no, it just discards the unused sg entries, the difference from 
sg->nents to sg->orig_nents.

What you thought it does could be called i915_sg_coalesce, optimize, or 
something. Maybe it would make sense to add this kind of helper if there 
are sufficient users. It should be doable in place without too much 
trouble I think.

Regards,

Tvrtko

>> Contrary to the
>> rotated remap, this one should actually benefit a lot from it. (For this
>> reason rotated remap does not bother to try it - it would be some luck
>> to find consecutive pages after rotation.)
>>
>> Regards,
>>
>> Tvrtko
>>
>>> +			sg = sg_next(sg);
>>> +		}
>>> +		offset += stride;
>>> +	}
>>> +
>>> +	return sg;
>>> +}
>>> +
>>> +static noinline struct sg_table *
>>> +intel_remap_pages(struct intel_remapped_info *rem_info,
>>> +		  struct drm_i915_gem_object *obj)
>>> +{
>>> +	unsigned int size = intel_remapped_info_size(rem_info);
>>> +	struct sg_table *st;
>>> +	struct scatterlist *sg;
>>> +	int ret = -ENOMEM;
>>> +	int i;
>>> +
>>> +	/* Allocate target SG list. */
>>> +	st = kmalloc(sizeof(*st), GFP_KERNEL);
>>> +	if (!st)
>>> +		goto err_st_alloc;
>>> +
>>> +	ret = sg_alloc_table(st, size, GFP_KERNEL);
>>> +	if (ret)
>>> +		goto err_sg_alloc;
>>> +
>>> +	st->nents = 0;
>>> +	sg = st->sgl;
>>> +
>>> +	for (i = 0 ; i < ARRAY_SIZE(rem_info->plane); i++) {
>>> +		sg = remap_pages(obj, rem_info->plane[i].offset,
>>> +				 rem_info->plane[i].width, rem_info->plane[i].height,
>>> +				 rem_info->plane[i].stride, st, sg);
>>> +	}
>>> +
>>> +	i915_sg_trim(st);
>>> +
>>> +	return st;
>>> +
>>> +err_sg_alloc:
>>> +	kfree(st);
>>> +err_st_alloc:
>>> +
>>> +	DRM_DEBUG_DRIVER("Failed to create remapped mapping for object size %zu! (%ux%u tiles, %u pages)\n",
>>> +			 obj->base.size, rem_info->plane[0].width, rem_info->plane[0].height, size);
>>> +
>>> +	return ERR_PTR(ret);
>>> +}
>>> +
>>>    static noinline struct sg_table *
>>>    intel_partial_pages(const struct i915_ggtt_view *view,
>>>    		    struct drm_i915_gem_object *obj)
>>> @@ -3783,6 +3852,11 @@ i915_get_ggtt_vma_pages(struct i915_vma *vma)
>>>    			intel_rotate_pages(&vma->ggtt_view.rotated, vma->obj);
>>>    		break;
>>>    
>>> +	case I915_GGTT_VIEW_REMAPPED:
>>> +		vma->pages =
>>> +			intel_remap_pages(&vma->ggtt_view.remapped, vma->obj);
>>> +		break;
>>> +
>>>    	case I915_GGTT_VIEW_PARTIAL:
>>>    		vma->pages = intel_partial_pages(&vma->ggtt_view, vma->obj);
>>>    		break;
>>> diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
>>> index 7e2af5f4f39b..69a22f57e6ca 100644
>>> --- a/drivers/gpu/drm/i915/i915_gem_gtt.h
>>> +++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
>>> @@ -160,11 +160,18 @@ typedef u64 gen8_ppgtt_pml4e_t;
>>>    
>>>    struct sg_table;
>>>    
>>> +struct intel_remapped_plane_info {
>>> +	/* in gtt pages */
>>> +	unsigned int width, height, stride, offset;
>>> +} __packed;
>>> +
>>> +struct intel_remapped_info {
>>> +	struct intel_remapped_plane_info plane[2];
>>> +	unsigned int unused_mbz;
>>> +} __packed;
>>> +
>>>    struct intel_rotation_info {
>>> -	struct intel_rotation_plane_info {
>>> -		/* tiles */
>>> -		unsigned int width, height, stride, offset;
>>> -	} plane[2];
>>> +	struct intel_remapped_plane_info plane[2];
>>>    } __packed;
>>>    
>>>    struct intel_partial_info {
>>> @@ -176,12 +183,20 @@ enum i915_ggtt_view_type {
>>>    	I915_GGTT_VIEW_NORMAL = 0,
>>>    	I915_GGTT_VIEW_ROTATED = sizeof(struct intel_rotation_info),
>>>    	I915_GGTT_VIEW_PARTIAL = sizeof(struct intel_partial_info),
>>> +	I915_GGTT_VIEW_REMAPPED = sizeof(struct intel_remapped_info),
>>>    };
>>>    
>>>    static inline void assert_i915_gem_gtt_types(void)
>>>    {
>>>    	BUILD_BUG_ON(sizeof(struct intel_rotation_info) != 8*sizeof(unsigned int));
>>>    	BUILD_BUG_ON(sizeof(struct intel_partial_info) != sizeof(u64) + sizeof(unsigned int));
>>> +	BUILD_BUG_ON(sizeof(struct intel_remapped_info) != 9*sizeof(unsigned int));
>>> +
>>> +	/* Check that rotation/remapped shares offsets for simplicity */
>>> +	BUILD_BUG_ON(offsetof(struct intel_remapped_info, plane[0]) !=
>>> +		     offsetof(struct intel_rotation_info, plane[0]));
>>> +	BUILD_BUG_ON(offsetofend(struct intel_remapped_info, plane[1]) !=
>>> +		     offsetofend(struct intel_rotation_info, plane[1]));
>>>    
>>>    	/* As we encode the size of each branch inside the union into its type,
>>>    	 * we have to be careful that each branch has a unique size.
>>> @@ -190,6 +205,7 @@ static inline void assert_i915_gem_gtt_types(void)
>>>    	case I915_GGTT_VIEW_NORMAL:
>>>    	case I915_GGTT_VIEW_PARTIAL:
>>>    	case I915_GGTT_VIEW_ROTATED:
>>> +	case I915_GGTT_VIEW_REMAPPED:
>>>    		/* gcc complains if these are identical cases */
>>>    		break;
>>>    	}
>>> @@ -201,6 +217,7 @@ struct i915_ggtt_view {
>>>    		/* Members need to contain no holes/padding */
>>>    		struct intel_partial_info partial;
>>>    		struct intel_rotation_info rotated;
>>> +		struct intel_remapped_info remapped;
>>>    	};
>>>    };
>>>    
>>> diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
>>> index 82652c3d1bed..2070e44eaa03 100644
>>> --- a/drivers/gpu/drm/i915/i915_vma.c
>>> +++ b/drivers/gpu/drm/i915/i915_vma.c
>>> @@ -164,6 +164,9 @@ vma_create(struct drm_i915_gem_object *obj,
>>>    		} else if (view->type == I915_GGTT_VIEW_ROTATED) {
>>>    			vma->size = intel_rotation_info_size(&view->rotated);
>>>    			vma->size <<= PAGE_SHIFT;
>>> +		} else if (view->type == I915_GGTT_VIEW_REMAPPED) {
>>> +			vma->size = intel_remapped_info_size(&view->remapped);
>>> +			vma->size <<= PAGE_SHIFT;
>>>    		}
>>>    	}
>>>    
>>> @@ -464,7 +467,8 @@ void __i915_vma_set_map_and_fenceable(struct i915_vma *vma)
>>>    	 * Explicitly disable for rotated VMA since the display does not
>>>    	 * need the fence and the VMA is not accessible to other users.
>>>    	 */
>>> -	if (vma->ggtt_view.type == I915_GGTT_VIEW_ROTATED)
>>> +	if (vma->ggtt_view.type == I915_GGTT_VIEW_ROTATED ||
>>> +	    vma->ggtt_view.type == I915_GGTT_VIEW_REMAPPED)
>>>    		return;
>>>    
>>>    	fenceable = (vma->node.size >= vma->fence_size &&
>>> diff --git a/drivers/gpu/drm/i915/i915_vma.h b/drivers/gpu/drm/i915/i915_vma.h
>>> index 4f7c1c7599f4..64cf029c028a 100644
>>> --- a/drivers/gpu/drm/i915/i915_vma.h
>>> +++ b/drivers/gpu/drm/i915/i915_vma.h
>>> @@ -265,8 +265,11 @@ i915_vma_compare(struct i915_vma *vma,
>>>    	 */
>>>    	BUILD_BUG_ON(I915_GGTT_VIEW_NORMAL >= I915_GGTT_VIEW_PARTIAL);
>>>    	BUILD_BUG_ON(I915_GGTT_VIEW_PARTIAL >= I915_GGTT_VIEW_ROTATED);
>>> +	BUILD_BUG_ON(I915_GGTT_VIEW_ROTATED >= I915_GGTT_VIEW_REMAPPED);
>>>    	BUILD_BUG_ON(offsetof(typeof(*view), rotated) !=
>>>    		     offsetof(typeof(*view), partial));
>>> +	BUILD_BUG_ON(offsetof(typeof(*view), rotated) !=
>>> +		     offsetof(typeof(*view), remapped));
>>>    	return memcmp(&vma->ggtt_view.partial, &view->partial, view->type);
>>>    }
>>>    
>>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
>>> index 8a0b477a69d3..41f7e0795b14 100644
>>> --- a/drivers/gpu/drm/i915/intel_display.c
>>> +++ b/drivers/gpu/drm/i915/intel_display.c
>>> @@ -1957,6 +1957,17 @@ unsigned int intel_rotation_info_size(const struct intel_rotation_info *rot_info
>>>    	return size;
>>>    }
>>>    
>>> +unsigned int intel_remapped_info_size(const struct intel_remapped_info *rem_info)
>>> +{
>>> +	unsigned int size = 0;
>>> +	int i;
>>> +
>>> +	for (i = 0 ; i < ARRAY_SIZE(rem_info->plane); i++)
>>> +		size += rem_info->plane[i].width * rem_info->plane[i].height;
>>> +
>>> +	return size;
>>> +}
>>> +
>>>    static void
>>>    intel_fill_fb_ggtt_view(struct i915_ggtt_view *view,
>>>    			const struct drm_framebuffer *fb,
>>> diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
>>> index 0e9a926fca04..6993eff5dfaf 100644
>>> --- a/drivers/gpu/drm/i915/intel_drv.h
>>> +++ b/drivers/gpu/drm/i915/intel_drv.h
>>> @@ -1523,6 +1523,7 @@ unsigned int intel_fb_xy_to_linear(int x, int y,
>>>    void intel_add_fb_offsets(int *x, int *y,
>>>    			  const struct intel_plane_state *state, int plane);
>>>    unsigned int intel_rotation_info_size(const struct intel_rotation_info *rot_info);
>>> +unsigned int intel_remapped_info_size(const struct intel_remapped_info *rem_info);
>>>    bool intel_has_pending_fb_unpin(struct drm_i915_private *dev_priv);
>>>    void intel_mark_busy(struct drm_i915_private *dev_priv);
>>>    void intel_mark_idle(struct drm_i915_private *dev_priv);
>>> diff --git a/drivers/gpu/drm/i915/selftests/i915_vma.c b/drivers/gpu/drm/i915/selftests/i915_vma.c
>>> index ffa74290e054..4fc49c27f13c 100644
>>> --- a/drivers/gpu/drm/i915/selftests/i915_vma.c
>>> +++ b/drivers/gpu/drm/i915/selftests/i915_vma.c
>>> @@ -395,8 +395,8 @@ assert_rotated(struct drm_i915_gem_object *obj,
>>>    	return sg;
>>>    }
>>>    
>>> -static unsigned int rotated_size(const struct intel_rotation_plane_info *a,
>>> -				 const struct intel_rotation_plane_info *b)
>>> +static unsigned int rotated_size(const struct intel_remapped_plane_info *a,
>>> +				 const struct intel_remapped_plane_info *b)
>>>    {
>>>    	return a->width * a->height + b->width * b->height;
>>>    }
>>> @@ -406,7 +406,7 @@ static int igt_vma_rotate(void *arg)
>>>    	struct drm_i915_private *i915 = arg;
>>>    	struct i915_address_space *vm = &i915->ggtt.vm;
>>>    	struct drm_i915_gem_object *obj;
>>> -	const struct intel_rotation_plane_info planes[] = {
>>> +	const struct intel_remapped_plane_info planes[] = {
>>>    		{ .width = 1, .height = 1, .stride = 1 },
>>>    		{ .width = 2, .height = 2, .stride = 2 },
>>>    		{ .width = 4, .height = 4, .stride = 4 },
>>>
> 
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