linux-kernel - [PATCH v2] PCI: endpoint: Use DMA channel's 'dev' for dma_map

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Date:   Tue, 16 Nov 2021 19:53:42 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Kishon Vijay Abraham I <kishon@...com>
Subject: [PATCH v2] PCI: endpoint: Use DMA channel's 'dev' for dma_map_single()

For the case where the pci-epf-test driver uses DMA for transferring
data to the root complex device, dma_map_single() is used to map virtual
address to a physical address (address accessible by DMA controller) and
provided to the DMAengine API for transferring data. Here instead of
using the PCIe endpoint controller's 'dev' for dma_map_single(), provide
DMA channel's 'dev' for dma_map_single() since the data transfer is
actually done by DMA.

Signed-off-by: Kishon Vijay Abraham I <kishon@...com>
---
Changes from v1:
Use dmaengine_get_dma_device() to get dma device from channel
V1: https://lore.kernel.org/r/20211115044944.31103-1-kishon@ti.com
 drivers/pci/endpoint/functions/pci-epf-test.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 90d84d3bc868..51f5b0b7b225 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -314,12 +314,12 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
 	u32 crc32;
 	bool use_dma;
 	phys_addr_t phys_addr;
+	struct device *dma_dev;
 	phys_addr_t dst_phys_addr;
 	struct timespec64 start, end;
 	struct pci_epf *epf = epf_test->epf;
 	struct device *dev = &epf->dev;
 	struct pci_epc *epc = epf->epc;
-	struct device *dma_dev = epf->epc->dev.parent;
 	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
 	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
 
@@ -353,6 +353,7 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
 			goto err_dma_map;
 		}
 
+		dma_dev = dmaengine_get_dma_device(epf_test->dma_chan);
 		dst_phys_addr = dma_map_single(dma_dev, buf, reg->size,
 					       DMA_FROM_DEVICE);
 		if (dma_mapping_error(dma_dev, dst_phys_addr)) {
@@ -402,12 +403,12 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test)
 	void *buf;
 	bool use_dma;
 	phys_addr_t phys_addr;
+	struct device *dma_dev;
 	phys_addr_t src_phys_addr;
 	struct timespec64 start, end;
 	struct pci_epf *epf = epf_test->epf;
 	struct device *dev = &epf->dev;
 	struct pci_epc *epc = epf->epc;
-	struct device *dma_dev = epf->epc->dev.parent;
 	enum pci_barno test_reg_bar = epf_test->test_reg_bar;
 	struct pci_epf_test_reg *reg = epf_test->reg[test_reg_bar];
 
@@ -444,6 +445,7 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test)
 			goto err_map_addr;
 		}
 
+		dma_dev = dmaengine_get_dma_device(epf_test->dma_chan);
 		src_phys_addr = dma_map_single(dma_dev, buf, reg->size,
 					       DMA_TO_DEVICE);
 		if (dma_mapping_error(dma_dev, src_phys_addr)) {
-- 
2.17.1