The calls to dma_map_sg() were passing sg_nents() for the @nents
parameter, then error-ing out if more than one @nr_sgs were
returned. Furthermore, there are no use-cases for iaa_crypto that allow
multiple SG lists to be mapped for dma at once.

Moreover, as per Herbert's direction in [1] for the batching API from
higher mm layers to interface with crypto using SG lists, batching
within iaa_crypto will rely on there being exactly one SG list per
"unit" of [de]compression in a batch, where the component SG lists are
obtained by breaking down the @req->src and @req->dst.

Given all of the above, this patch simplifies the design by expecting
only 1 @nents in req->src and req->dst, which aligns with current and
batching use cases that will be developed in subsequent patches.

This alleviates the latency penalty of calling sg_nents() per
[de]compress op submitted to the hardware.

Some unlikely() annotations are added to conditionals in the core
[de]compress routines to further improve latency per op.

[1]: https://lore.kernel.org/all/aJ7Fk6RpNc815Ivd@gondor.apana.org.au/T/#m99aea2ce3d284e6c5a3253061d97b08c4752a798

Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@intel.com>
---
 drivers/crypto/intel/iaa/iaa_crypto_main.c | 54 +++++++++++-----------
 1 file changed, 27 insertions(+), 27 deletions(-)

diff --git a/drivers/crypto/intel/iaa/iaa_crypto_main.c b/drivers/crypto/intel/iaa/iaa_crypto_main.c
index dd7c4831e092..16b071058f2b 100644
--- a/drivers/crypto/intel/iaa/iaa_crypto_main.c
+++ b/drivers/crypto/intel/iaa/iaa_crypto_main.c
@@ -1514,11 +1514,11 @@ static int iaa_remap_for_verify(struct device *dev, struct iaa_wq *iaa_wq,
 	int ret = 0;
 	int nr_sgs;
 
-	dma_unmap_sg(dev, req->dst, sg_nents(req->dst), DMA_FROM_DEVICE);
-	dma_unmap_sg(dev, req->src, sg_nents(req->src), DMA_TO_DEVICE);
+	dma_unmap_sg(dev, req->dst, 1, DMA_FROM_DEVICE);
+	dma_unmap_sg(dev, req->src, 1, DMA_TO_DEVICE);
 
-	nr_sgs = dma_map_sg(dev, req->src, sg_nents(req->src), DMA_FROM_DEVICE);
-	if (nr_sgs <= 0 || nr_sgs > 1) {
+	nr_sgs = dma_map_sg(dev, req->src, 1, DMA_FROM_DEVICE);
+	if (unlikely(nr_sgs <= 0 || nr_sgs > 1)) {
 		dev_dbg(dev, "verify: couldn't map src sg for iaa device %d,"
 			" wq %d: ret=%d\n", iaa_wq->iaa_device->idxd->id,
 			iaa_wq->wq->id, ret);
@@ -1530,13 +1530,13 @@ static int iaa_remap_for_verify(struct device *dev, struct iaa_wq *iaa_wq,
 		" req->slen %d, sg_dma_len(sg) %d\n", *src_addr, nr_sgs,
 		req->src, req->slen, sg_dma_len(req->src));
 
-	nr_sgs = dma_map_sg(dev, req->dst, sg_nents(req->dst), DMA_TO_DEVICE);
-	if (nr_sgs <= 0 || nr_sgs > 1) {
+	nr_sgs = dma_map_sg(dev, req->dst, 1, DMA_TO_DEVICE);
+	if (unlikely(nr_sgs <= 0 || nr_sgs > 1)) {
 		dev_dbg(dev, "verify: couldn't map dst sg for iaa device %d,"
 			" wq %d: ret=%d\n", iaa_wq->iaa_device->idxd->id,
 			iaa_wq->wq->id, ret);
 		ret = -EIO;
-		dma_unmap_sg(dev, req->src, sg_nents(req->src), DMA_FROM_DEVICE);
+		dma_unmap_sg(dev, req->src, 1, DMA_FROM_DEVICE);
 		goto out;
 	}
 	*dst_addr = sg_dma_address(req->dst);
@@ -1704,14 +1704,14 @@ static void iaa_desc_complete(struct idxd_desc *idxd_desc,
 			err = -EIO;
 		}
 
-		dma_unmap_sg(dev, ctx->req->dst, sg_nents(ctx->req->dst), DMA_TO_DEVICE);
-		dma_unmap_sg(dev, ctx->req->src, sg_nents(ctx->req->src), DMA_FROM_DEVICE);
+		dma_unmap_sg(dev, ctx->req->dst, 1, DMA_TO_DEVICE);
+		dma_unmap_sg(dev, ctx->req->src, 1, DMA_FROM_DEVICE);
 
 		goto out;
 	}
 err:
-	dma_unmap_sg(dev, ctx->req->dst, sg_nents(ctx->req->dst), DMA_FROM_DEVICE);
-	dma_unmap_sg(dev, ctx->req->src, sg_nents(ctx->req->src), DMA_TO_DEVICE);
+	dma_unmap_sg(dev, ctx->req->dst, 1, DMA_FROM_DEVICE);
+	dma_unmap_sg(dev, ctx->req->src, 1, DMA_TO_DEVICE);
 out:
 	if (ret != 0)
 		dev_dbg(dev, "asynchronous compress failed ret=%d\n", ret);
@@ -2014,8 +2014,8 @@ static int iaa_comp_acompress(struct acomp_req *req)
 
 	dev = &wq->idxd->pdev->dev;
 
-	nr_sgs = dma_map_sg(dev, req->src, sg_nents(req->src), DMA_TO_DEVICE);
-	if (nr_sgs <= 0 || nr_sgs > 1) {
+	nr_sgs = dma_map_sg(dev, req->src, 1, DMA_TO_DEVICE);
+	if (unlikely(nr_sgs <= 0 || nr_sgs > 1)) {
 		dev_dbg(dev, "couldn't map src sg for iaa device %d,"
 			" wq %d: ret=%d\n", iaa_wq->iaa_device->idxd->id,
 			iaa_wq->wq->id, ret);
@@ -2024,8 +2024,8 @@ static int iaa_comp_acompress(struct acomp_req *req)
 	}
 	src_addr = sg_dma_address(req->src);
 
-	nr_sgs = dma_map_sg(dev, req->dst, sg_nents(req->dst), DMA_FROM_DEVICE);
-	if (nr_sgs <= 0 || nr_sgs > 1) {
+	nr_sgs = dma_map_sg(dev, req->dst, 1, DMA_FROM_DEVICE);
+	if (unlikely(nr_sgs <= 0 || nr_sgs > 1)) {
 		dev_dbg(dev, "couldn't map dst sg for iaa device %d,"
 			" wq %d: ret=%d\n", iaa_wq->iaa_device->idxd->id,
 			iaa_wq->wq->id, ret);
@@ -2051,18 +2051,18 @@ static int iaa_comp_acompress(struct acomp_req *req)
 		if (ret)
 			dev_dbg(dev, "asynchronous compress verification failed ret=%d\n", ret);
 
-		dma_unmap_sg(dev, req->dst, sg_nents(req->dst), DMA_TO_DEVICE);
-		dma_unmap_sg(dev, req->src, sg_nents(req->src), DMA_FROM_DEVICE);
+		dma_unmap_sg(dev, req->dst, 1, DMA_TO_DEVICE);
+		dma_unmap_sg(dev, req->src, 1, DMA_FROM_DEVICE);
 
 		goto out;
 	}
 
-	if (ret)
+	if (unlikely(ret))
 		dev_dbg(dev, "asynchronous compress failed ret=%d\n", ret);
 
-	dma_unmap_sg(dev, req->dst, sg_nents(req->dst), DMA_FROM_DEVICE);
+	dma_unmap_sg(dev, req->dst, 1, DMA_FROM_DEVICE);
 err_map_dst:
-	dma_unmap_sg(dev, req->src, sg_nents(req->src), DMA_TO_DEVICE);
+	dma_unmap_sg(dev, req->src, 1, DMA_TO_DEVICE);
 out:
 	percpu_ref_put(&iaa_wq->ref);
 
@@ -2095,8 +2095,8 @@ static int iaa_comp_adecompress(struct acomp_req *req)
 
 	dev = &wq->idxd->pdev->dev;
 
-	nr_sgs = dma_map_sg(dev, req->src, sg_nents(req->src), DMA_TO_DEVICE);
-	if (nr_sgs <= 0 || nr_sgs > 1) {
+	nr_sgs = dma_map_sg(dev, req->src, 1, DMA_TO_DEVICE);
+	if (unlikely(nr_sgs <= 0 || nr_sgs > 1)) {
 		dev_dbg(dev, "couldn't map src sg for iaa device %d,"
 			" wq %d: ret=%d\n", iaa_wq->iaa_device->idxd->id,
 			iaa_wq->wq->id, ret);
@@ -2105,8 +2105,8 @@ static int iaa_comp_adecompress(struct acomp_req *req)
 	}
 	src_addr = sg_dma_address(req->src);
 
-	nr_sgs = dma_map_sg(dev, req->dst, sg_nents(req->dst), DMA_FROM_DEVICE);
-	if (nr_sgs <= 0 || nr_sgs > 1) {
+	nr_sgs = dma_map_sg(dev, req->dst, 1, DMA_FROM_DEVICE);
+	if (unlikely(nr_sgs <= 0 || nr_sgs > 1)) {
 		dev_dbg(dev, "couldn't map dst sg for iaa device %d,"
 			" wq %d: ret=%d\n", iaa_wq->iaa_device->idxd->id,
 			iaa_wq->wq->id, ret);
@@ -2120,12 +2120,12 @@ static int iaa_comp_adecompress(struct acomp_req *req)
 	if (ret == -EINPROGRESS)
 		return ret;
 
-	if (ret != 0)
+	if (unlikely(ret != 0))
 		dev_dbg(dev, "asynchronous decompress failed ret=%d\n", ret);
 
-	dma_unmap_sg(dev, req->dst, sg_nents(req->dst), DMA_FROM_DEVICE);
+	dma_unmap_sg(dev, req->dst, 1, DMA_FROM_DEVICE);
 err_map_dst:
-	dma_unmap_sg(dev, req->src, sg_nents(req->src), DMA_TO_DEVICE);
+	dma_unmap_sg(dev, req->src, 1, DMA_TO_DEVICE);
 out:
 	percpu_ref_put(&iaa_wq->ref);
 
-- 
2.27.0