mtd: rawnand: stm32_fmc2: Fix dma_map_sg error check

dma_map_sg return 0 on error, in case of error return -EIO.

Cc: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Vignesh Raghavendra <vigneshr@ti.com>
Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com>
Cc: Alexandre Torgue <alexandre.torgue@foss.st.com>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Christophe Kerello <christophe.kerello@foss.st.com>
Cc: Cai Huoqing <cai.huoqing@linux.dev>
Cc: linux-mtd@lists.infradead.org
Cc: linux-stm32@st-md-mailman.stormreply.com
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Jack Wang <jinpu.wang@ionos.com>
Reviewed-by: Christophe Kerello <christophe.kerello@foss.st.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220819060801.10443-5-jinpu.wang@ionos.com

drivers/mtd/nand/raw/stm32_fmc2_nand.c

@@ -862,8 +862,8 @@ static int stm32_fmc2_nfc_xfer(struct nand_chip *chip, const u8 *buf,
 
 	ret = dma_map_sg(nfc->dev, nfc->dma_data_sg.sgl,
 			 eccsteps, dma_data_dir);
-	if (ret < 0)
-		return ret;
+	if (!ret)
+		return -EIO;
 
 	desc_data = dmaengine_prep_slave_sg(dma_ch, nfc->dma_data_sg.sgl,
 					    eccsteps, dma_transfer_dir,
@@ -893,8 +893,10 @@ static int stm32_fmc2_nfc_xfer(struct nand_chip *chip, const u8 *buf,
 
 		ret = dma_map_sg(nfc->dev, nfc->dma_ecc_sg.sgl,
 				 eccsteps, dma_data_dir);
-		if (ret < 0)
+		if (!ret) {
+			ret = -EIO;
 			goto err_unmap_data;
+		}
 
 		desc_ecc = dmaengine_prep_slave_sg(nfc->dma_ecc_ch,
 						   nfc->dma_ecc_sg.sgl,