[PATCH 3/3] drm/ttm/dma: Optimize when free-ing the recycled page pool.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

We would free the page pool - even if it was for cached pages
(which are deleted from the pool - so there are no free pages).

Also we also missed the opportunity to batch the amount of pages
to free (similar to how ttm_page_alloc.c does it). This reintroduces
the code that was lost during rebasing.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
---
 drivers/gpu/drm/ttm/ttm_page_alloc_dma.c |    9 ++++++---
 1 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
index e57aa24..156ddcd 100644
--- a/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
+++ b/drivers/gpu/drm/ttm/ttm_page_alloc_dma.c
@@ -949,7 +949,7 @@ void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 	struct dma_page *d_page, *next;
 	enum pool_type type;
 	bool is_cached = false;
-	unsigned count = 0, i, npages;
+	unsigned count = 0, i, npages = 0;
 	unsigned long irq_flags;
 
 	type = ttm_to_type(ttm->page_flags, ttm->caching_state);
@@ -971,13 +971,16 @@ void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 	pool->npages_in_use -= count;
 	if (is_cached) {
 		pool->nfrees += count;
-		npages = count;
 	} else {
 		pool->npages_free += count;
 		list_splice(&ttm_dma->pages_list, &pool->free_list);
 		npages = count;
 		if (pool->npages_free > _manager->options.max_size) {
 			npages = pool->npages_free - _manager->options.max_size;
+			/* free at least NUM_PAGES_TO_ALLOC number of pages
+			 * to reduce calls to set_memory_wb */
+			if (npages < NUM_PAGES_TO_ALLOC)
+				npages = NUM_PAGES_TO_ALLOC;
 		}
 	}
 	spin_unlock_irqrestore(&pool->lock, irq_flags);
@@ -1001,7 +1004,7 @@ void ttm_dma_unpopulate(struct ttm_dma_tt *ttm_dma, struct device *dev)
 		ttm_dma->dma_address[i] = 0;
 	}
 
-	/* shrink pool if necessary */
+	/* shrink pool if necessary (only on !is_cached pools)*/
 	if (npages)
 		ttm_dma_page_pool_free(pool, npages);
 	ttm->state = tt_unpopulated;
-- 
1.7.7.3