drm/etnaviv: add cmdbuf suballocator

There are 3 big benefits to suballocating a single big DMA buffer
for command submission:

1. Avoid hammering CMA. The old way of allocating and freeing a DMA
   buffer for each submission was hitting some of the real slow
   pathes in CMA, as this allocator was not designed for a concurrent
   small buffers load.

2. Less TLB flushes on IOMMUv2. If a new command buffer is mapped into
   the GPU address space the MMU TLBs need to be flushed. By having
   one big buffer statically mapped to the GPU, a lot of those flushes
   can be avoided.

3. No funky workarounds for GC3000. The FE TLB flush on GC3000 isn't
   reliable. To work around that we tried to lay out the cmdbufs in
   the GPU address space in a way to avoid this issue. This hasn't
   always worked if the address space is crowded. A single statically
   mapped buffer avoids the erratum completely.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Christian Gmeiner <christian.gmeiner@gmail.com>

1 files changed, 106 insertions, 17 deletions

diff --git a/drivers/gpu/drm/etnaviv/etnaviv_cmdbuf.c b/drivers/gpu/drm/etnaviv/etnaviv_cmdbuf.c
index 1ad118c..633e0f0 100644
--- a/drivers/gpu/drm/etnaviv/etnaviv_cmdbuf.c
+++ b/drivers/gpu/drm/etnaviv/etnaviv_cmdbuf.c
@@ -14,51 +14,140 @@
  * this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <drm/drm_mm.h>
+
 #include "etnaviv_cmdbuf.h"
 #include "etnaviv_gpu.h"
 #include "etnaviv_mmu.h"
 
-struct etnaviv_cmdbuf *etnaviv_cmdbuf_new(struct etnaviv_gpu *gpu, u32 size,
-	size_t nr_bos)
+#define SUBALLOC_SIZE		SZ_256K
+#define SUBALLOC_GRANULE	SZ_4K
+#define SUBALLOC_GRANULES	(SUBALLOC_SIZE / SUBALLOC_GRANULE)
+
+struct etnaviv_cmdbuf_suballoc {
+	/* suballocated dma buffer properties */
+	struct etnaviv_gpu *gpu;
+	void *vaddr;
+	dma_addr_t paddr;
+
+	/* GPU mapping */
+	u32 iova;
+	struct drm_mm_node vram_node; /* only used on MMUv2 */
+
+	/* allocation management */
+	struct mutex lock;
+	DECLARE_BITMAP(granule_map, SUBALLOC_GRANULES);
+	int free_space;
+	wait_queue_head_t free_event;
+};
+
+struct etnaviv_cmdbuf_suballoc *
+etnaviv_cmdbuf_suballoc_new(struct etnaviv_gpu * gpu)
+{
+	struct etnaviv_cmdbuf_suballoc *suballoc;
+	int ret;
+
+	suballoc = kzalloc(sizeof(*suballoc), GFP_KERNEL);
+	if (!suballoc)
+		return ERR_PTR(-ENOMEM);
+
+	suballoc->gpu = gpu;
+	mutex_init(&suballoc->lock);
+	init_waitqueue_head(&suballoc->free_event);
+
+	suballoc->vaddr = dma_alloc_wc(gpu->dev, SUBALLOC_SIZE,
+				       &suballoc->paddr, GFP_KERNEL);
+	if (!suballoc->vaddr)
+		goto free_suballoc;
+
+	ret = etnaviv_iommu_get_suballoc_va(gpu, suballoc->paddr,
+					    &suballoc->vram_node, SUBALLOC_SIZE,
+					    &suballoc->iova);
+	if (ret)
+		goto free_dma;
+
+	return suballoc;
+
+free_dma:
+	dma_free_wc(gpu->dev, SUBALLOC_SIZE, suballoc->vaddr, suballoc->paddr);
+free_suballoc:
+	kfree(suballoc);
+
+	return NULL;
+}
+
+void etnaviv_cmdbuf_suballoc_destroy(struct etnaviv_cmdbuf_suballoc *suballoc)
+{
+	etnaviv_iommu_put_suballoc_va(suballoc->gpu, &suballoc->vram_node,
+				      SUBALLOC_SIZE, suballoc->iova);
+	dma_free_wc(suballoc->gpu->dev, SUBALLOC_SIZE, suballoc->vaddr,
+		    suballoc->paddr);
+	kfree(suballoc);
+}
+
+struct etnaviv_cmdbuf *
+etnaviv_cmdbuf_new(struct etnaviv_cmdbuf_suballoc *suballoc, u32 size,
+		   size_t nr_bos)
 {
 	struct etnaviv_cmdbuf *cmdbuf;
 	size_t sz = size_vstruct(nr_bos, sizeof(cmdbuf->bo_map[0]),
 				 sizeof(*cmdbuf));
+	int granule_offs, order, ret;
 
 	cmdbuf = kzalloc(sz, GFP_KERNEL);
 	if (!cmdbuf)
 		return NULL;
 
-	if (gpu->mmu->version == ETNAVIV_IOMMU_V2)
-		size = ALIGN(size, SZ_4K);
+	cmdbuf->suballoc = suballoc;
+	cmdbuf->size = size;
 
-	cmdbuf->vaddr = dma_alloc_wc(gpu->dev, size, &cmdbuf->paddr,
-				     GFP_KERNEL);
-	if (!cmdbuf->vaddr) {
-		kfree(cmdbuf);
-		return NULL;
+	order = order_base_2(ALIGN(size, SUBALLOC_GRANULE) / SUBALLOC_GRANULE);
+retry:
+	mutex_lock(&suballoc->lock);
+	granule_offs = bitmap_find_free_region(suballoc->granule_map,
+					SUBALLOC_GRANULES, order);
+	if (granule_offs < 0) {
+		suballoc->free_space = 0;
+		mutex_unlock(&suballoc->lock);
+		ret = wait_event_interruptible_timeout(suballoc->free_event,
+						       suballoc->free_space,
+						       msecs_to_jiffies(10 * 1000));
+		if (!ret) {
+			dev_err(suballoc->gpu->dev,
+				"Timeout waiting for cmdbuf space\n");
+			return NULL;
+		}
+		goto retry;
 	}
-
-	cmdbuf->gpu = gpu;
-	cmdbuf->size = size;
+	mutex_unlock(&suballoc->lock);
+	cmdbuf->suballoc_offset = granule_offs * SUBALLOC_GRANULE;
+	cmdbuf->vaddr = suballoc->vaddr + cmdbuf->suballoc_offset;
 
 	return cmdbuf;
 }
 
 void etnaviv_cmdbuf_free(struct etnaviv_cmdbuf *cmdbuf)
 {
-	etnaviv_iommu_put_cmdbuf_va(cmdbuf->gpu, cmdbuf);
-	dma_free_wc(cmdbuf->gpu->dev, cmdbuf->size, cmdbuf->vaddr,
-		    cmdbuf->paddr);
+	struct etnaviv_cmdbuf_suballoc *suballoc = cmdbuf->suballoc;
+	int order = order_base_2(ALIGN(cmdbuf->size, SUBALLOC_GRANULE) /
+				 SUBALLOC_GRANULE);
+
+	mutex_lock(&suballoc->lock);
+	bitmap_release_region(suballoc->granule_map,
+			      cmdbuf->suballoc_offset / SUBALLOC_GRANULE,
+			      order);
+	suballoc->free_space = 1;
+	mutex_unlock(&suballoc->lock);
+	wake_up_all(&suballoc->free_event);
 	kfree(cmdbuf);
 }
 
 u32 etnaviv_cmdbuf_get_va(struct etnaviv_cmdbuf *buf)
 {
-	return etnaviv_iommu_get_cmdbuf_va(buf->gpu, buf);
+	return buf->suballoc->iova + buf->suballoc_offset;
 }
 
 dma_addr_t etnaviv_cmdbuf_get_pa(struct etnaviv_cmdbuf *buf)
 {
-	return buf->paddr;
+	return buf->suballoc->paddr + buf->suballoc_offset;
 }