dmaengine: sdxi: completion: Use dma pool for sdxi_cst_blk

This has been a TODO for a while. Replace the wasteful
dma_alloc_coherent() for every 32-byte completion status block with
allocation from a pool.

Signed-off-by: Nathan Lynch <nathan.lynch@amd.com>

Author: nathanlynch

drivers/dma/sdxi/completion.c

@@ -1,6 +1,7 @@
 #include <linux/cleanup.h>
-#include <linux/slab.h>
 #include <linux/dma-mapping.h>
+#include <linux/dmapool.h>
+#include <linux/slab.h>
 
 #include "completion.h"
 #include "descriptor.h"
@@ -24,9 +25,7 @@ struct sdxi_completion *sdxi_completion_alloc(struct sdxi_dev *sdxi)
 	if (!sc)
 		return NULL;
 
-	/* Should use a dma_pool. */
-	cst_blk = dma_alloc_coherent(sdxi_to_dev(sdxi), sizeof(*cst_blk),
-				     &cst_blk_dma, GFP_NOWAIT);
+	cst_blk = dma_pool_zalloc(sdxi->cst_blk_pool, GFP_NOWAIT, &cst_blk_dma);
 	if (!cst_blk)
 		return NULL;
 
@@ -43,8 +42,7 @@ struct sdxi_completion *sdxi_completion_alloc(struct sdxi_dev *sdxi)
 
 void sdxi_completion_free(struct sdxi_completion *sc)
 {
-	dma_free_coherent(sdxi_to_dev(sc->sdxi), sizeof(*sc->cst_blk),
-			  sc->cst_blk, sc->cst_blk_dma);
+	dma_pool_free(sc->sdxi->cst_blk_pool, sc->cst_blk, sc->cst_blk_dma);
 	kfree(sc);
 }
 

drivers/dma/sdxi/device.c

@@ -306,6 +306,9 @@ static int sdxi_device_init(struct sdxi_dev *sdxi)
 	if (sdxi_create_dma_pool(sdxi, &sdxi->cxt_ctl_pool,
 				 "CXT_CTL", sizeof(struct sdxi_cxt_ctl)))
 		return -ENOMEM;
+	if (sdxi_create_dma_pool(sdxi, &sdxi->cst_blk_pool,
+				 "CST_BLK", sizeof(struct sdxi_cst_blk)))
+		return -ENOMEM;
 
 	err = sdxi_fn_activate(sdxi);
 	if (err)

drivers/dma/sdxi/sdxi.h

@@ -124,6 +124,7 @@ struct sdxi_dev {
 	struct dma_pool *write_index_pool;
 	struct dma_pool *cxt_sts_pool;
 	struct dma_pool *cxt_ctl_pool;
+	struct dma_pool *cst_blk_pool;
 
 	unsigned int nr_vectors;
 	struct ida vectors;