Re: [PATCH 1/4] drm/i915: Clearing buffer objects via blitter engine

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

Hi,

On 07/01/2015 10:25 AM, ankitprasad.r.sharma@intel.com wrote:
> From: Ankitprasad Sharma <ankitprasad.r.sharma@intel.com>
>
> This patch adds support for clearing buffer objects via blitter
> engines. This is particularly useful for clearing out the memory
> from stolen region.

Because CPU cannot access it? I would put that into the commit message 
since I think cover letter does not go into the git history.

> v2: Add support for using execlists & PPGTT
>
> v3: Fix issues in legacy ringbuffer submission mode
>
> v4: Rebased to the latest drm-intel-nightly (Ankit)
>
> testcase: igt/gem_stolen
>

Nitpick: usually it is "Testcase:" and all tags grouped together.

> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Deepak S <deepak.s at linux.intel.com>
> Signed-off-by: Ankitprasad Sharma <ankitprasad.r.sharma at intel.com>
> ---
>   drivers/gpu/drm/i915/Makefile           |   1 +
>   drivers/gpu/drm/i915/i915_drv.h         |   4 +
>   drivers/gpu/drm/i915/i915_gem_exec.c    | 201 ++++++++++++++++++++++++++++++++
>   drivers/gpu/drm/i915/intel_lrc.c        |   4 +-
>   drivers/gpu/drm/i915/intel_lrc.h        |   3 +
>   drivers/gpu/drm/i915/intel_ringbuffer.c |   2 +-
>   drivers/gpu/drm/i915/intel_ringbuffer.h |   1 +
>   7 files changed, 213 insertions(+), 3 deletions(-)
>   create mode 100644 drivers/gpu/drm/i915/i915_gem_exec.c
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index de21965..1959314 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -24,6 +24,7 @@ i915-y += i915_cmd_parser.o \
>   	  i915_gem_debug.o \
>   	  i915_gem_dmabuf.o \
>   	  i915_gem_evict.o \
> +	  i915_gem_exec.o \
>   	  i915_gem_execbuffer.o \
>   	  i915_gem_gtt.o \
>   	  i915_gem.o \
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index ea9caf2..d1e151e 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -3082,6 +3082,10 @@ int __must_check i915_gem_evict_something(struct drm_device *dev,
>   int i915_gem_evict_vm(struct i915_address_space *vm, bool do_idle);
>   int i915_gem_evict_everything(struct drm_device *dev);
>
> +/* i915_gem_exec.c */
> +int i915_gem_exec_clear_object(struct drm_i915_gem_object *obj,
> +			       struct drm_i915_file_private *file_priv);
> +
>   /* belongs in i915_gem_gtt.h */
>   static inline void i915_gem_chipset_flush(struct drm_device *dev)
>   {
> diff --git a/drivers/gpu/drm/i915/i915_gem_exec.c b/drivers/gpu/drm/i915/i915_gem_exec.c
> new file mode 100644
> index 0000000..a07fda0
> --- /dev/null
> +++ b/drivers/gpu/drm/i915/i915_gem_exec.c
> @@ -0,0 +1,201 @@
> +/*
> + * Copyright © 2013 Intel Corporation

Is the year correct?

> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + *
> + * Authors:
> + *    Chris Wilson <chris at chris-wilson.co.uk>

And author?

> + *
> + */
> +
> +#include <drm/drmP.h>
> +#include <drm/i915_drm.h>
> +#include "i915_drv.h"
> +
> +#define GEN8_COLOR_BLT_CMD (2<<29 | 0x50<<22)
> +
> +#define BPP_8 0
> +#define BPP_16 (1<<24)
> +#define BPP_32 (1<<25 | 1<<24)
> +
> +#define ROP_FILL_COPY (0xf0 << 16)
> +
> +static int i915_gem_exec_flush_object(struct drm_i915_gem_object *obj,
> +				      struct intel_engine_cs *ring,
> +				      struct intel_context *ctx,
> +				      struct drm_i915_gem_request **req)
> +{
> +	int ret;
> +
> +	ret = i915_gem_object_sync(obj, ring, req);
> +	if (ret)
> +		return ret;
> +
> +	if (obj->base.write_domain & I915_GEM_DOMAIN_CPU) {
> +		if (i915_gem_clflush_object(obj, false))
> +			i915_gem_chipset_flush(obj->base.dev);
> +		obj->base.write_domain &= ~I915_GEM_DOMAIN_CPU;
> +	}
> +	if (obj->base.write_domain & I915_GEM_DOMAIN_GTT) {
> +		wmb();
> +		obj->base.write_domain &= ~I915_GEM_DOMAIN_GTT;
> +	}

All this could be replaced with i915_gem_object_set_to_gtt_domain, no?

> +
> +	return i915.enable_execlists ?
> +			logical_ring_invalidate_all_caches(*req) :
> +			intel_ring_invalidate_all_caches(*req);

And this is done on actual submission for you by the lower levels so you 
don't need to call it directly.

> +}
> +
> +static void i915_gem_exec_dirty_object(struct drm_i915_gem_object *obj,
> +				       struct intel_engine_cs *ring,
> +				       struct i915_address_space *vm,
> +				       struct drm_i915_gem_request *req)
> +{
> +	i915_gem_request_assign(&obj->last_write_req, req);
> +	obj->base.read_domains = I915_GEM_DOMAIN_RENDER;
> +	obj->base.write_domain = I915_GEM_DOMAIN_RENDER;
> +	i915_vma_move_to_active(i915_gem_obj_to_vma(obj, vm), req);
> +	obj->dirty = 1;
> +
> +	ring->gpu_caches_dirty = true;
> +}
> +
> +int i915_gem_exec_clear_object(struct drm_i915_gem_object *obj,
> +			       struct drm_i915_file_private *file_priv)
> +{

Function needs some good kerneldoc.

> +	struct drm_device *dev = obj->base.dev;
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	struct intel_engine_cs *ring;
> +	struct intel_context *ctx;
> +	struct intel_ringbuffer *ringbuf;
> +	struct i915_address_space *vm;
> +	struct drm_i915_gem_request *req;
> +	int ret = 0;
> +
> +	lockdep_assert_held(&dev->struct_mutex);

It think there was some guidance that lockdep_assert_held is compiled 
out when lockdep is not in the kernel and that WARN_ON is preferred. In 
this case that would probably be WARN_ON_ONCE and return error.

> +
> +	ring = &dev_priv->ring[HAS_BLT(dev) ? BCS : RCS];
> +	ctx = i915_gem_context_get(file_priv, DEFAULT_CONTEXT_HANDLE);
> +	/* Allocate a request for this operation nice and early. */
> +	ret = i915_gem_request_alloc(ring, ctx, &req);
> +	if (ret)
> +		return ret;
> +
> +	if (ctx->ppgtt)
> +		vm = &ctx->ppgtt->base;
> +	else
> +		vm = &dev_priv->gtt.base;
> +
> +	if (i915.enable_execlists && !ctx->engine[ring->id].state) {
> +		ret = intel_lr_context_deferred_create(ctx, ring);

i915_gem_context_get above and this call are very similar to what 
i915_gem_validate_context does. It seems to me it would be better to 
call the latter function here.

> +		if (ret)
> +			return ret;

Failure path (and some below) leaks the request. i915_gem_request_cancel 
is the new API to be called I understand.

> +	}
> +
> +	ringbuf = ctx->engine[ring->id].ringbuf;
> +
> +	ret = i915_gem_object_pin(obj, vm, PAGE_SIZE, 0);
> +	if (ret)
> +		return ret;
> +
> +	if (obj->tiling_mode && INTEL_INFO(dev)->gen <= 3) {
> +		ret = i915_gem_object_put_fence(obj);
> +		if (ret)
> +			goto unpin;
> +	}

Why is this needed?

Could it be called unconditionally and still work?

At least I would recommend a comment explaining it.

> +	ret = i915_gem_exec_flush_object(obj, ring, ctx, &req);
> +	if (ret)
> +		goto unpin;

As I said above one call to i915_gem_object_set_to_gtt_domain would be 
enough I think.

> +	if (i915.enable_execlists) {
> +		if (dev_priv->info.gen >= 8) {
> +			ret = intel_logical_ring_begin(req, 8);
> +			if (ret)
> +				goto unpin;
> +
> +			intel_logical_ring_emit(ringbuf, GEN8_COLOR_BLT_CMD |
> +							 BLT_WRITE_RGBA |
> +							 (7-2));
> +			intel_logical_ring_emit(ringbuf, BPP_32 |
> +							 ROP_FILL_COPY |
> +							 PAGE_SIZE);
> +			intel_logical_ring_emit(ringbuf, 0);
> +			intel_logical_ring_emit(ringbuf,
> +						obj->base.size >> PAGE_SHIFT
> +						<< 16 | PAGE_SIZE / 4);
> +			intel_logical_ring_emit(ringbuf,
> +						i915_gem_obj_offset(obj, vm));
> +			intel_logical_ring_emit(ringbuf, 0);
> +			intel_logical_ring_emit(ringbuf, 0);
> +			intel_logical_ring_emit(ringbuf, MI_NOOP);
> +
> +			intel_logical_ring_advance(ringbuf);
> +		} else {
> +			DRM_ERROR("Execlists not supported for gen %d\n",
> +				  dev_priv->info.gen);
> +			ret = -EINVAL;

I would put a WARN_ON_ONCE here, or even just return -EINVAL. If the 
driver is so messed up in general that execlists are enabled < gen8 I 
think there is no point logging errors about it from here. Would also 
save you one indentation level.

> +			goto unpin;
> +		}
> +	} else {
> +		if (IS_GEN8(dev)) {
> +			ret = intel_ring_begin(req, 8);
> +			if (ret)
> +				goto unpin;
> +
> +			intel_ring_emit(ring, GEN8_COLOR_BLT_CMD |
> +					      BLT_WRITE_RGBA | (7-2));
> +			intel_ring_emit(ring, BPP_32 |
> +					      ROP_FILL_COPY | PAGE_SIZE);
> +			intel_ring_emit(ring, 0);
> +			intel_ring_emit(ring,
> +					obj->base.size >> PAGE_SHIFT << 16 |
> +					PAGE_SIZE / 4);
> +			intel_ring_emit(ring, i915_gem_obj_offset(obj, vm));
> +			intel_ring_emit(ring, 0);
> +			intel_ring_emit(ring, 0);
> +			intel_ring_emit(ring, MI_NOOP);

Such a pitty that these two emit blocks need to be duplicated but I 
guess it is what it is now.

> +		} else {
> +			ret = intel_ring_begin(req, 6);
> +			if (ret)
> +				goto unpin;
> +
> +			intel_ring_emit(ring, COLOR_BLT_CMD |
> +					      BLT_WRITE_RGBA);
> +			intel_ring_emit(ring, BPP_32 |
> +					      ROP_FILL_COPY | PAGE_SIZE);
> +			intel_ring_emit(ring,
> +					obj->base.size >> PAGE_SHIFT << 16 |
> +					PAGE_SIZE);
> +			intel_ring_emit(ring, i915_gem_obj_offset(obj, vm));
> +			intel_ring_emit(ring, 0);
> +			intel_ring_emit(ring, MI_NOOP);
> +		}
> +
> +		__intel_ring_advance(ring);
> +	}
> +
> +	i915_gem_exec_dirty_object(obj, ring, vm, req);

Where is this request actually submitted?

Regards,

Tvrtko
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