[PATCH v11 8/8] PCI: endpoint: Enable DMA tests for endpoints with DMA capabilities

[Frank Li <Frank.Li@nxp.com>]

Some PCI Endpoints controllers integrate an eDMA (embedded DMA).
eDMA only sends once a bus read/write command to complete once
data transfer. eDMA can bypass the outbound memory address translation
unit to access all RC memory space.

Add DMA support for pci-epf-test.

EPF test can use, depending on HW availability, eDMA or general system
DMA controllers to perform DMA. The test probes the EPF DMA channel
capabilities.

Separate dma_chan to dma_chan_tx and dma_chan_rx. eDMA channels have
higher priority than general DMA channels. If general memory to memory
DMA hannels are used, dma_chan_rx = dma_chan_tx.

Add dma_addr_t dma_remote in function pci_epf_test_data_transfer()
because eDMA using remote RC physical address directly

Add enum dma_transfer_direction dir in function pci_epf_test_data_transfer()
because eDMA chooses the correct RX/TX channel by dir.

The overall steps are

1. Execute dma_request_channel() and filter function to find correct eDMA
RX and TX Channel. If a channel does not exist,  fallback to try to allocate
general memory to memory DMA  channel.
2. Execute dmaengine_slave_config() to configure remote side physical address.
3. Execute dmaengine_prep_slave_single() to create transfer descriptor.
4. Execute tx_submit().
5. Execute dma_async_issue_pending()

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Acked-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
Change from v10 to v11:
 - rewrite commit message
Change from v9 to v10:
 - rewrite commit message
Change from v4 to v9:
 - none
Change from v3 to v4:
 - reverse Xmas tree order
 - local -> dma_local
 - change error message
 - IS_ERR -> IS_ERR_OR_NULL
 - check return value of dmaengine_slave_config()
Change from v1 to v2:
 - none

 drivers/pci/endpoint/functions/pci-epf-test.c | 108 ++++++++++++++++--
 1 file changed, 98 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
index 90d84d3bc868f..f26afd02f3a86 100644
--- a/drivers/pci/endpoint/functions/pci-epf-test.c
+++ b/drivers/pci/endpoint/functions/pci-epf-test.c
@@ -52,9 +52,11 @@ struct pci_epf_test {
 	enum pci_barno		test_reg_bar;
 	size_t			msix_table_offset;
 	struct delayed_work	cmd_handler;
-	struct dma_chan		*dma_chan;
+	struct dma_chan		*dma_chan_tx;
+	struct dma_chan		*dma_chan_rx;
 	struct completion	transfer_complete;
 	bool			dma_supported;
+	bool			dma_private;
 	const struct pci_epc_features *epc_features;
 };
 
@@ -105,12 +107,15 @@ static void pci_epf_test_dma_callback(void *param)
  */
 static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
 				      dma_addr_t dma_dst, dma_addr_t dma_src,
-				      size_t len)
+				      size_t len, dma_addr_t dma_remote,
+				      enum dma_transfer_direction dir)
 {
+	struct dma_chan *chan = (dir == DMA_DEV_TO_MEM) ? epf_test->dma_chan_tx : epf_test->dma_chan_rx;
+	dma_addr_t dma_local = (dir == DMA_MEM_TO_DEV) ? dma_src : dma_dst;
 	enum dma_ctrl_flags flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
-	struct dma_chan *chan = epf_test->dma_chan;
 	struct pci_epf *epf = epf_test->epf;
 	struct dma_async_tx_descriptor *tx;
+	struct dma_slave_config sconf = {};
 	struct device *dev = &epf->dev;
 	dma_cookie_t cookie;
 	int ret;
@@ -120,7 +125,22 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
 		return -EINVAL;
 	}
 
-	tx = dmaengine_prep_dma_memcpy(chan, dma_dst, dma_src, len, flags);
+	if (epf_test->dma_private) {
+		sconf.direction = dir;
+		if (dir == DMA_MEM_TO_DEV)
+			sconf.dst_addr = dma_remote;
+		else
+			sconf.src_addr = dma_remote;
+
+		if (dmaengine_slave_config(chan, &sconf)) {
+			dev_err(dev, "DMA slave config fail\n");
+			return -EIO;
+		}
+		tx = dmaengine_prep_slave_single(chan, dma_local, len, dir, flags);
+	} else {
+		tx = dmaengine_prep_dma_memcpy(chan, dma_dst, dma_src, len, flags);
+	}
+
 	if (!tx) {
 		dev_err(dev, "Failed to prepare DMA memcpy\n");
 		return -EIO;
@@ -148,6 +168,23 @@ static int pci_epf_test_data_transfer(struct pci_epf_test *epf_test,
 	return 0;
 }
 
+struct epf_dma_filter {
+	struct device *dev;
+	u32 dma_mask;
+};
+
+static bool epf_dma_filter_fn(struct dma_chan *chan, void *node)
+{
+	struct epf_dma_filter *filter = node;
+	struct dma_slave_caps caps;
+
+	memset(&caps, 0, sizeof(caps));
+	dma_get_slave_caps(chan, &caps);
+
+	return chan->device->dev == filter->dev
+		&& (filter->dma_mask & caps.directions);
+}
+
 /**
  * pci_epf_test_init_dma_chan() - Function to initialize EPF test DMA channel
  * @epf_test: the EPF test device that performs data transfer operation
@@ -158,10 +195,44 @@ static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
 {
 	struct pci_epf *epf = epf_test->epf;
 	struct device *dev = &epf->dev;
+	struct epf_dma_filter filter;
 	struct dma_chan *dma_chan;
 	dma_cap_mask_t mask;
 	int ret;
 
+	filter.dev = epf->epc->dev.parent;
+	filter.dma_mask = BIT(DMA_DEV_TO_MEM);
+
+	dma_cap_zero(mask);
+	dma_cap_set(DMA_SLAVE, mask);
+	dma_chan = dma_request_channel(mask, epf_dma_filter_fn, &filter);
+	if (IS_ERR_OR_NULL(dma_chan)) {
+		dev_info(dev, "Failed to get private DMA channel. Falling back to generic one\n");
+		goto fail_back_tx;
+	}
+
+	epf_test->dma_chan_rx = dma_chan;
+
+	filter.dma_mask = BIT(DMA_MEM_TO_DEV);
+	dma_chan = dma_request_channel(mask, epf_dma_filter_fn, &filter);
+
+	if (IS_ERR(dma_chan)) {
+		dev_info(dev, "Failed to get private DMA channel. Falling back to generic one\n");
+		goto fail_back_rx;
+	}
+
+	epf_test->dma_chan_tx = dma_chan;
+	epf_test->dma_private = true;
+
+	init_completion(&epf_test->transfer_complete);
+
+	return 0;
+
+fail_back_rx:
+	dma_release_channel(epf_test->dma_chan_rx);
+	epf_test->dma_chan_tx = NULL;
+
+fail_back_tx:
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_MEMCPY, mask);
 
@@ -174,7 +245,7 @@ static int pci_epf_test_init_dma_chan(struct pci_epf_test *epf_test)
 	}
 	init_completion(&epf_test->transfer_complete);
 
-	epf_test->dma_chan = dma_chan;
+	epf_test->dma_chan_tx = epf_test->dma_chan_rx = dma_chan;
 
 	return 0;
 }
@@ -190,8 +261,17 @@ static void pci_epf_test_clean_dma_chan(struct pci_epf_test *epf_test)
 	if (!epf_test->dma_supported)
 		return;
 
-	dma_release_channel(epf_test->dma_chan);
-	epf_test->dma_chan = NULL;
+	dma_release_channel(epf_test->dma_chan_tx);
+	if (epf_test->dma_chan_tx == epf_test->dma_chan_rx) {
+		epf_test->dma_chan_tx = NULL;
+		epf_test->dma_chan_rx = NULL;
+		return;
+	}
+
+	dma_release_channel(epf_test->dma_chan_rx);
+	epf_test->dma_chan_rx = NULL;
+
+	return;
 }
 
 static void pci_epf_test_print_rate(const char *ops, u64 size,
@@ -280,8 +360,14 @@ static int pci_epf_test_copy(struct pci_epf_test *epf_test)
 			goto err_map_addr;
 		}
 
+		if (epf_test->dma_private) {
+			dev_err(dev, "Cannot transfer data using DMA\n");
+			ret = -EINVAL;
+			goto err_map_addr;
+		}
+
 		ret = pci_epf_test_data_transfer(epf_test, dst_phys_addr,
-						 src_phys_addr, reg->size);
+						 src_phys_addr, reg->size, 0, DMA_MEM_TO_MEM);
 		if (ret)
 			dev_err(dev, "Data transfer failed\n");
 	} else {
@@ -363,7 +449,8 @@ static int pci_epf_test_read(struct pci_epf_test *epf_test)
 
 		ktime_get_ts64(&start);
 		ret = pci_epf_test_data_transfer(epf_test, dst_phys_addr,
-						 phys_addr, reg->size);
+						 phys_addr, reg->size,
+						 reg->src_addr, DMA_DEV_TO_MEM);
 		if (ret)
 			dev_err(dev, "Data transfer failed\n");
 		ktime_get_ts64(&end);
@@ -453,8 +540,9 @@ static int pci_epf_test_write(struct pci_epf_test *epf_test)
 		}
 
 		ktime_get_ts64(&start);
+
 		ret = pci_epf_test_data_transfer(epf_test, phys_addr,
-						 src_phys_addr, reg->size);
+						 src_phys_addr, reg->size, reg->dst_addr, DMA_MEM_TO_DEV);
 		if (ret)
 			dev_err(dev, "Data transfer failed\n");
 		ktime_get_ts64(&end);
-- 
2.35.1