[PATCH 13/22] drm/i915: add support for 64K scratch page

Matthew Auld
2017-08-15T18:17:03Z

Before we can fully enable 64K pages, we need to first support a 64K
scratch page if we intend to support the case where we have object sizes
< 2M, since any scratch PTE must also point to a 64K region. Without
this our 64K usage is limited to objects which completely fill the
page-table, and therefore don't need any scratch.

Reported-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_gem_gtt.c | 61 +++++++++++++++++++++++++++++++++++--
drivers/gpu/drm/i915/i915_gem_gtt.h | 1 +
2 files changed, 60 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.c b/drivers/gpu/drm/i915/i915_gem_gtt.c
index aeef20a9ea0a..a2178c33586c 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.c
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.c
@@ -475,12 +475,69 @@ static void fill_page_dma_32(struct i915_address_space *vm,
static int
setup_scratch_page(struct i915_address_space *vm, gfp_t gfp)
{
- return __setup_page_dma(vm, &vm->scratch_page, gfp | __GFP_ZERO);
+ struct page *page = NULL;
+ dma_addr_t addr;
+ int order;
+
+ /* In order to utilize 64K pages for an object with a size < 2M, we will
+ * need to support a 64K scratch page, given that every 16th entry for a
+ * page-table operating in 64K mode must point to a properly aligned 64K
+ * region, including any PTEs which happen to point to scratch.
+ *
+ * XXX: should we rather make the scratch global, does it have to be
+ * per-vm?
+ */
+ if (i915_vm_is_48bit(vm) &&
+ HAS_PAGE_SIZE(vm->i915, I915_GTT_PAGE_SIZE_64K)) {
+ order = get_order(I915_GTT_PAGE_SIZE_64K);
+ page = alloc_pages(gfp | __GFP_ZERO, order);
+ if (page) {
+ addr = dma_map_page(vm->dma, page, 0,
+ I915_GTT_PAGE_SIZE_64K,
+ PCI_DMA_BIDIRECTIONAL);
+ if (unlikely(dma_mapping_error(vm->dma, addr))) {
+ __free_pages(page, order);
+ page = NULL;
+ }
+
+ if (!IS_ALIGNED(addr, I915_GTT_PAGE_SIZE_64K)) {
+ dma_unmap_page(vm->dma, addr,
+ I915_GTT_PAGE_SIZE_64K,
+ PCI_DMA_BIDIRECTIONAL);
+ __free_pages(page, order);
+ page = NULL;
+ }
+ }
+ }
+
+ if (!page) {
+ order = 0;
+ page = alloc_page(gfp | __GFP_ZERO);
+ if (unlikely(!page))
+ return -ENOMEM;
+
+ addr = dma_map_page(vm->dma, page, 0, PAGE_SIZE,
+ PCI_DMA_BIDIRECTIONAL);
+ if (unlikely(dma_mapping_error(vm->dma, addr))) {
+ __free_page(page);
+ return -ENOMEM;
+ }
+ }
+
+ vm->scratch_page.page = page;
+ vm->scratch_page.daddr = addr;
+ vm->scratch_page.order = order;
+
+ return 0;
}

static void cleanup_scratch_page(struct i915_address_space *vm)
{
- cleanup_page_dma(vm, &vm->scratch_page);
+ struct i915_page_dma *p = &vm->scratch_page;
+
+ dma_unmap_page(vm->dma, p->daddr, BIT(p->order) << PAGE_SHIFT,
+ PCI_DMA_BIDIRECTIONAL);
+ __free_pages(p->page, p->order);
}

static struct i915_page_table *alloc_pt(struct i915_address_space *vm)
diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index aa4488637fc9..356fec26e8c9 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -212,6 +212,7 @@ struct i915_vma;

struct i915_page_dma {
struct page *page;
+ int order;
union {
dma_addr_t daddr;