drm/i915/gt: Switch to object allocations for page directories

The GEM object is grossly overweight for the practicality of tracking
large numbers of individual pages, yet it is currently our only
abstraction for tracking DMA allocations. Since those allocations need
to be reserved upfront before an operation, and that we need to break
away from simple system memory, we need to ditch using plain struct page
wrappers.

In the process, we drop the WC mapping as we ended up clflushing
everything anyway due to various issues across a wider range of
platforms. Though in a future step, we need to drop the kmap_atomic
approach which suggests we need to pre-map all the pages and keep them
mapped.

v2: Verify our large scratch page is suitably DMA aligned; and manually
clear the scratch since we are allocating plain struct pages full of
prior content.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200729164219.5737-2-chris@chris-wilson.co.uk
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

1 files changed, 12 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/i915_vma.c b/drivers/gpu/drm/i915/i915_vma.c
index a9e79b67035e..c6bf04ca2032 100644
--- a/drivers/gpu/drm/i915/i915_vma.c
+++ b/drivers/gpu/drm/i915/i915_vma.c
@@ -872,24 +872,30 @@ int i915_vma_pin(struct i915_vma *vma, u64 size, u64 alignment, u64 flags)
 	if (err)
 		return err;
 
+	if (flags & PIN_GLOBAL)
+		wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm);
+
 	if (flags & vma->vm->bind_async_flags) {
 		work = i915_vma_work();
 		if (!work) {
 			err = -ENOMEM;
-			goto err_pages;
+			goto err_rpm;
 		}
 
 		work->vm = i915_vm_get(vma->vm);
 
 		/* Allocate enough page directories to used PTE */
-		if (vma->vm->allocate_va_range)
+		if (vma->vm->allocate_va_range) {
 			i915_vm_alloc_pt_stash(vma->vm,
 					       &work->stash,
 					       vma->size);
-	}
 
-	if (flags & PIN_GLOBAL)
-		wakeref = intel_runtime_pm_get(&vma->vm->i915->runtime_pm);
+			err = i915_vm_pin_pt_stash(vma->vm,
+						   &work->stash);
+			if (err)
+				goto err_fence;
+		}
+	}
 
 	/*
 	 * Differentiate between user/kernel vma inside the aliasing-ppgtt.
@@ -978,9 +984,9 @@ err_unlock:
 err_fence:
 	if (work)
 		dma_fence_work_commit_imm(&work->base);
+err_rpm:
 	if (wakeref)
 		intel_runtime_pm_put(&vma->vm->i915->runtime_pm, wakeref);
-err_pages:
 	vma_put_pages(vma);
 	return err;
 }