linux-kernel - [PATCH v2 6/8] nvmet: pci-epf: Use dmaengine_prep_config_single

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Message-Id: <20251218-dma_prep_config-v2-6-c07079836128@nxp.com>
Date: Thu, 18 Dec 2025 10:56:26 -0500
From: Frank Li <Frank.Li@....com>
To: Vinod Koul <vkoul@...nel.org>, Manivannan Sadhasivam <mani@...nel.org>, 
 Krzysztof Wilczyński <kwilczynski@...nel.org>, 
 Kishon Vijay Abraham I <kishon@...nel.org>, 
 Bjorn Helgaas <bhelgaas@...gle.com>, Christoph Hellwig <hch@....de>, 
 Sagi Grimberg <sagi@...mberg.me>, Chaitanya Kulkarni <kch@...dia.com>, 
 Herbert Xu <herbert@...dor.apana.org.au>, 
 "David S. Miller" <davem@...emloft.net>, 
 Nicolas Ferre <nicolas.ferre@...rochip.com>, 
 Alexandre Belloni <alexandre.belloni@...tlin.com>, 
 Claudiu Beznea <claudiu.beznea@...on.dev>, Koichiro Den <den@...inux.co.jp>, 
 Niklas Cassel <cassel@...nel.org>
Cc: dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-pci@...r.kernel.org, linux-nvme@...ts.infradead.org, 
 mhi@...ts.linux.dev, linux-arm-msm@...r.kernel.org, 
 linux-crypto@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, 
 imx@...ts.linux.dev, Frank Li <Frank.Li@....com>
Subject: [PATCH v2 6/8] nvmet: pci-epf: Use
 dmaengine_prep_config_single_safe() API

Use the new dmaengine_prep_config_single_safe() API to combine the
configuration and descriptor preparation into a single call.

Since dmaengine_prep_config_single_safe() performs the configuration and
preparation atomically and dw edma driver implement prep_config_sg() call
back, so dmaengine_prep_config_single() is reentriable, the mutex can be
removed.

Tested-by: Niklas Cassel <cassel@...nel.org>
Signed-off-by: Frank Li <Frank.Li@....com>
---
 drivers/nvme/target/pci-epf.c | 18 ++++--------------
 1 file changed, 4 insertions(+), 14 deletions(-)

diff --git a/drivers/nvme/target/pci-epf.c b/drivers/nvme/target/pci-epf.c
index 56b1c6a7706a9e2dd9d8aaf17b440129b948486c..8b5ea5d4c79dfd461b767cfd4033a9e4604c94b1 100644
--- a/drivers/nvme/target/pci-epf.c
+++ b/drivers/nvme/target/pci-epf.c
@@ -388,22 +388,15 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
 		return -EINVAL;
 	}

-	mutex_lock(lock);
-
 	dma_dev = dmaengine_get_dma_device(chan);
 	dma_addr = dma_map_single(dma_dev, seg->buf, seg->length, dir);
 	ret = dma_mapping_error(dma_dev, dma_addr);
 	if (ret)
-		goto unlock;
-
-	ret = dmaengine_slave_config(chan, &sconf);
-	if (ret) {
-		dev_err(dev, "Failed to configure DMA channel\n");
-		goto unmap;
-	}
+		return ret;

-	desc = dmaengine_prep_slave_single(chan, dma_addr, seg->length,
-					   sconf.direction, DMA_CTRL_ACK);
+	desc = dmaengine_prep_config_single_safe(chan, dma_addr, seg->length,
+						 sconf.direction,
+						 DMA_CTRL_ACK, &sconf);
 	if (!desc) {
 		dev_err(dev, "Failed to prepare DMA\n");
 		ret = -EIO;
@@ -426,9 +419,6 @@ static int nvmet_pci_epf_dma_transfer(struct nvmet_pci_epf *nvme_epf,
 unmap:
 	dma_unmap_single(dma_dev, dma_addr, seg->length, dir);

-unlock:
-	mutex_unlock(lock);
-
 	return ret;
 }

-- 
2.34.1