[PATCH v2 4/4] dma-pool: Make sure atomic pool suits device

[Nicolas Saenz Julienne]

When allocating DMA memory from a pool, the core can only guess which
atomic pool will fit a device's constraints. If it doesn't, get a safer
atomic pool and try again.

Fixes: c84dc6e68a1d ("dma-pool: add additional coherent pools to map to gfp mask")
Reported-by: Jeremy Linton <jeremy.linton at arm.com>
Suggested-by: Robin Murphy <robin.murphy at arm.com>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne at suse.de>
---

Changes since v1:
 - Rebase to linus' master

 kernel/dma/pool.c | 57 ++++++++++++++++++++++++++++++-----------------
 1 file changed, 37 insertions(+), 20 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 5b9eaa2b498d..d48d9acb585f 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -240,39 +240,56 @@ static inline struct gen_pool *dma_guess_pool(struct device *dev,
 void *dma_alloc_from_pool(struct device *dev, size_t size,
 			  struct page **ret_page, gfp_t flags)
 {
-	struct gen_pool *pool = dma_guess_pool(dev, NULL);
-	unsigned long val;
+	struct gen_pool *pool = NULL;
+	unsigned long val = 0;
 	void *ptr = NULL;
-
-	if (!pool) {
-		WARN(1, "%pGg atomic pool not initialised!\n", &flags);
-		return NULL;
+	phys_addr_t phys;
+
+	while (1) {
+		pool = dma_guess_pool(dev, pool);
+		if (!pool) {
+			WARN(1, "Failed to get suitable pool for %s\n",
+			     dev_name(dev));
+			break;
+		}
+
+		val = gen_pool_alloc(pool, size);
+		if (!val)
+			continue;
+
+		phys = gen_pool_virt_to_phys(pool, val);
+		if (dma_coherent_ok(dev, phys, size))
+			break;
+
+		gen_pool_free(pool, val, size);
+		val = 0;
 	}
 
-	val = gen_pool_alloc(pool, size);
-	if (likely(val)) {
-		phys_addr_t phys = gen_pool_virt_to_phys(pool, val);
 
+	if (val) {
 		*ret_page = pfn_to_page(__phys_to_pfn(phys));
 		ptr = (void *)val;
 		memset(ptr, 0, size);
-	} else {
-		WARN_ONCE(1, "DMA coherent pool depleted, increase size "
-			     "(recommended min coherent_pool=%zuK)\n",
-			  gen_pool_size(pool) >> 9);
+
+		if (gen_pool_avail(pool) < atomic_pool_size)
+			schedule_work(&atomic_pool_work);
 	}
-	if (gen_pool_avail(pool) < atomic_pool_size)
-		schedule_work(&atomic_pool_work);
 
 	return ptr;
 }
 
 bool dma_free_from_pool(struct device *dev, void *start, size_t size)
 {
-	struct gen_pool *pool = dma_guess_pool(dev, NULL);
+	struct gen_pool *pool = NULL;
 
-	if (!pool || !gen_pool_has_addr(pool, (unsigned long)start, size))
-		return false;
-	gen_pool_free(pool, (unsigned long)start, size);
-	return true;
+	while (1) {
+		pool = dma_guess_pool(dev, pool);
+		if (!pool)
+			return false;
+
+		if (gen_pool_has_addr(pool, (unsigned long)start, size)) {
+			gen_pool_free(pool, (unsigned long)start, size);
+			return true;
+		}
+	}
 }
-- 
2.27.0