[PATCH] drm/i915: implement dma buf begin_cpu_access (v2)

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

In order for udl vmap to work properly, we need to push the object
into the CPU domain before we start copying the data to the USB device.

This along with the udl change avoids userspace explicit mapping to
be used.

v2: add a flag for userspace to query to know if Intel kernel driver can
deal with the vmap flushing properly. In theory udl would need a flag also,
but I intend to push the patches very close to each other and other drivers
should do the right thing from the start.

I've added a test to my intel-gpu-tools prime branch, however testing
this is a bit messy since the only way to get udl to vmap is to rendering
something. I've tested this with real code as well to make sure it works.

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 drivers/gpu/drm/i915/i915_dma.c        |    3 +++
 drivers/gpu/drm/i915/i915_gem_dmabuf.c |   17 +++++++++++++++++
 include/drm/i915_drm.h                 |    1 +
 3 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 36822b9..1a0e112 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -1006,6 +1006,9 @@ static int i915_getparam(struct drm_device *dev, void *data,
 	case I915_PARAM_HAS_ALIASING_PPGTT:
 		value = dev_priv->mm.aliasing_ppgtt ? 1 : 0;
 		break;
+	case I915_PARAM_HAS_PRIME_VMAP_FLUSH:
+		value = 1;
+		break;
 	default:
 		DRM_DEBUG_DRIVER("Unknown parameter %d\n",
 				 param->param);
diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
index cf6bdec..ee51c63 100644
--- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
@@ -147,6 +147,22 @@ static int i915_gem_dmabuf_mmap(struct dma_buf *dma_buf, struct vm_area_struct *
 	return -EINVAL;
 }
 
+static int i915_gem_begin_cpu_access(struct dma_buf *dma_buf, size_t start, size_t length, enum dma_data_direction direction)
+{
+	struct drm_i915_gem_object *obj = dma_buf->priv;
+	struct drm_device *dev = obj->base.dev;
+	int ret;
+	bool write = (direction == DMA_BIDIRECTIONAL || direction == DMA_TO_DEVICE);
+
+	ret = i915_mutex_lock_interruptible(dev);
+	if (ret)
+		return ret;
+
+	ret = i915_gem_object_set_to_cpu_domain(obj, write);
+	mutex_unlock(&dev->struct_mutex);
+	return ret;
+}
+
 static const struct dma_buf_ops i915_dmabuf_ops =  {
 	.map_dma_buf = i915_gem_map_dma_buf,
 	.unmap_dma_buf = i915_gem_unmap_dma_buf,
@@ -158,6 +174,7 @@ static const struct dma_buf_ops i915_dmabuf_ops =  {
 	.mmap = i915_gem_dmabuf_mmap,
 	.vmap = i915_gem_dmabuf_vmap,
 	.vunmap = i915_gem_dmabuf_vunmap,
+	.begin_cpu_access = i915_gem_begin_cpu_access,
 };
 
 struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
diff --git a/include/drm/i915_drm.h b/include/drm/i915_drm.h
index f3f8224..8df848b 100644
--- a/include/drm/i915_drm.h
+++ b/include/drm/i915_drm.h
@@ -298,6 +298,7 @@ typedef struct drm_i915_irq_wait {
 #define I915_PARAM_HAS_GEN7_SOL_RESET	 16
 #define I915_PARAM_HAS_LLC     	 	 17
 #define I915_PARAM_HAS_ALIASING_PPGTT	 18
+#define I915_PARAM_HAS_PRIME_VMAP_FLUSH	 19
 
 typedef struct drm_i915_getparam {
 	int param;
-- 
1.7.10.2