[PATCH v3 0/3] PLX Switch DMA Engine Driver

[PATCH v3 0/3] PLX Switch DMA Engine Driver

[Logan Gunthorpe]

This is v3 of the patchset. The in-use unbind bits have been sent and
accepted as a separate patch set. This patchset just includes the new
driver which has been updated to use the common reference counting.

This patchset is based off of vkoul/slave-dma.git/next and a git branch is
available here:

https://github.com/sbates130272/linux-p2pmem/ plx-dma-v3

Changes for v3:
* Common in-use unbind bits were submitted as a separate patch set
* Rebased onto vkoul/slave-dma.git/next (as of Jan 3rd 2020)

Changes for v2:

* Rebased onto v5.5-rc1 (no changes)
* Pushed the plx_dma_isr() routine into the patch that uses it (per
  Vinod's feedback)

Logan Gunthorpe (3):
  dmaengine: plx-dma: Introduce PLX DMA engine PCI driver skeleton
  dmaengine: plx-dma: Implement hardware initialization and cleanup
  dmaengine: plx-dma: Implement descriptor submission

 MAINTAINERS           |   5 +
 drivers/dma/Kconfig   |   9 +
 drivers/dma/Makefile  |   1 +
 drivers/dma/plx_dma.c | 639 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 654 insertions(+)
 create mode 100644 drivers/dma/plx_dma.c

--
2.20.1

[PATCH v3 1/3] dmaengine: plx-dma: Introduce PLX DMA engine PCI driver skeleton

[Logan Gunthorpe]

Some PLX Switches can expose DMA engines via extra PCI functions
on the upstream port. Each function will have one DMA channel.

This patch is just the core PCI driver skeleton and dma
engine registration.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 MAINTAINERS           |   5 ++
 drivers/dma/Kconfig   |   9 +++
 drivers/dma/Makefile  |   1 +
 drivers/dma/plx_dma.c | 150 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 165 insertions(+)
 create mode 100644 drivers/dma/plx_dma.c

diff --git a/MAINTAINERS b/MAINTAINERS
index bd5847e802de..76713226f256 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13139,6 +13139,11 @@ S:	Maintained
 F:	drivers/iio/chemical/pms7003.c
 F:	Documentation/devicetree/bindings/iio/chemical/plantower,pms7003.yaml
 
+PLX DMA DRIVER
+M:	Logan Gunthorpe <logang@deltatee.com>
+S:	Maintained
+F:	drivers/dma/plx_dma.c
+
 PMBUS HARDWARE MONITORING DRIVERS
 M:	Guenter Roeck <linux@roeck-us.net>
 L:	linux-hwmon@vger.kernel.org
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index 6fa1eba9d477..312a6cc36c78 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -497,6 +497,15 @@ config PXA_DMA
 	  16 to 32 channels for peripheral to memory or memory to memory
 	  transfers.
 
+config PLX_DMA
+	tristate "PLX ExpressLane PEX Switch DMA Engine Support"
+	depends on PCI
+	select DMA_ENGINE
+	help
+	  Some PLX ExpressLane PCI Switches support additional DMA engines.
+	  These are exposed via extra functions on the switch's
+	  upstream port. Each function exposes one DMA channel.
+
 config SIRF_DMA
 	tristate "CSR SiRFprimaII/SiRFmarco DMA support"
 	depends on ARCH_SIRF
diff --git a/drivers/dma/Makefile b/drivers/dma/Makefile
index 42d7e2fc64fa..a150d1d792fd 100644
--- a/drivers/dma/Makefile
+++ b/drivers/dma/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_NBPFAXI_DMA) += nbpfaxi.o
 obj-$(CONFIG_OWL_DMA) += owl-dma.o
 obj-$(CONFIG_PCH_DMA) += pch_dma.o
 obj-$(CONFIG_PL330_DMA) += pl330.o
+obj-$(CONFIG_PLX_DMA) += plx_dma.o
 obj-$(CONFIG_PPC_BESTCOMM) += bestcomm/
 obj-$(CONFIG_PXA_DMA) += pxa_dma.o
 obj-$(CONFIG_RENESAS_DMA) += sh/
diff --git a/drivers/dma/plx_dma.c b/drivers/dma/plx_dma.c
new file mode 100644
index 000000000000..e002cbb7d2b6
--- /dev/null
+++ b/drivers/dma/plx_dma.c
@@ -0,0 +1,150 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Microsemi Switchtec(tm) PCIe Management Driver
+ * Copyright (c) 2019, Logan Gunthorpe <logang@deltatee.com>
+ * Copyright (c) 2019, GigaIO Networks, Inc
+ */
+
+#include "dmaengine.h"
+
+#include <linux/dmaengine.h>
+#include <linux/kref.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/pci.h>
+
+MODULE_DESCRIPTION("PLX ExpressLane PEX PCI Switch DMA Engine");
+MODULE_VERSION("0.1");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Logan Gunthorpe");
+
+struct plx_dma_dev {
+	struct dma_device dma_dev;
+	struct dma_chan dma_chan;
+	void __iomem *bar;
+};
+
+static void plx_dma_release(struct dma_device *dma_dev)
+{
+	struct plx_dma_dev *plxdev =
+		container_of(dma_dev, struct plx_dma_dev, dma_dev);
+
+	put_device(dma_dev->dev);
+	kfree(plxdev);
+}
+
+static int plx_dma_create(struct pci_dev *pdev)
+{
+	struct plx_dma_dev *plxdev;
+	struct dma_device *dma;
+	struct dma_chan *chan;
+	int rc;
+
+	plxdev = kzalloc(sizeof(*plxdev), GFP_KERNEL);
+	if (!plxdev)
+		return -ENOMEM;
+
+	plxdev->bar = pcim_iomap_table(pdev)[0];
+
+	dma = &plxdev->dma_dev;
+	dma->chancnt = 1;
+	INIT_LIST_HEAD(&dma->channels);
+	dma->copy_align = DMAENGINE_ALIGN_1_BYTE;
+	dma->dev = get_device(&pdev->dev);
+
+	dma->device_release = plx_dma_release;
+
+	chan = &plxdev->dma_chan;
+	chan->device = dma;
+	dma_cookie_init(chan);
+	list_add_tail(&chan->device_node, &dma->channels);
+
+	rc = dma_async_device_register(dma);
+	if (rc) {
+		pci_err(pdev, "Failed to register dma device: %d\n", rc);
+		free_irq(pci_irq_vector(pdev, 0),  plxdev);
+		kfree(plxdev);
+		return rc;
+	}
+
+	pci_set_drvdata(pdev, plxdev);
+
+	return 0;
+}
+
+static int plx_dma_probe(struct pci_dev *pdev,
+			 const struct pci_device_id *id)
+{
+	int rc;
+
+	rc = pcim_enable_device(pdev);
+	if (rc)
+		return rc;
+
+	rc = pci_set_dma_mask(pdev, DMA_BIT_MASK(48));
+	if (rc)
+		rc = pci_set_dma_mask(pdev, DMA_BIT_MASK(32));
+	if (rc)
+		return rc;
+
+	rc = pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(48));
+	if (rc)
+		rc = pci_set_consistent_dma_mask(pdev, DMA_BIT_MASK(32));
+	if (rc)
+		return rc;
+
+	rc = pcim_iomap_regions(pdev, 1, KBUILD_MODNAME);
+	if (rc)
+		return rc;
+
+	rc = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
+	if (rc <= 0)
+		return rc;
+
+	pci_set_master(pdev);
+
+	rc = plx_dma_create(pdev);
+	if (rc)
+		goto err_free_irq_vectors;
+
+	pci_info(pdev, "PLX DMA Channel Registered\n");
+
+	return 0;
+
+err_free_irq_vectors:
+	pci_free_irq_vectors(pdev);
+	return rc;
+}
+
+static void plx_dma_remove(struct pci_dev *pdev)
+{
+	struct plx_dma_dev *plxdev = pci_get_drvdata(pdev);
+
+	free_irq(pci_irq_vector(pdev, 0),  plxdev);
+
+	plxdev->bar = NULL;
+	dma_async_device_unregister(&plxdev->dma_dev);
+
+	pci_free_irq_vectors(pdev);
+}
+
+static const struct pci_device_id plx_dma_pci_tbl[] = {
+	{
+		.vendor		= PCI_VENDOR_ID_PLX,
+		.device		= 0x87D0,
+		.subvendor	= PCI_ANY_ID,
+		.subdevice	= PCI_ANY_ID,
+		.class		= PCI_CLASS_SYSTEM_OTHER << 8,
+		.class_mask	= 0xFFFFFFFF,
+	},
+	{0}
+};
+MODULE_DEVICE_TABLE(pci, plx_dma_pci_tbl);
+
+static struct pci_driver plx_dma_pci_driver = {
+	.name           = KBUILD_MODNAME,
+	.id_table       = plx_dma_pci_tbl,
+	.probe          = plx_dma_probe,
+	.remove		= plx_dma_remove,
+};
+module_pci_driver(plx_dma_pci_driver);
-- 
2.20.1

[PATCH v3 2/3] dmaengine: plx-dma: Implement hardware initialization and cleanup

[Logan Gunthorpe]

Allocate DMA coherent memory for the ring of DMA descriptors and
program the appropriate hardware registers.

A tasklet is created which is triggered on an interrupt to process
all the finished requests. Additionally, any remaining descriptors
are aborted when the hardware is removed or the resources freed.

Use an RCU pointer to synchronize PCI device unbind.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/dma/plx_dma.c | 370 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 370 insertions(+)

diff --git a/drivers/dma/plx_dma.c b/drivers/dma/plx_dma.c
index e002cbb7d2b6..f3a5c9e47658 100644
--- a/drivers/dma/plx_dma.c
+++ b/drivers/dma/plx_dma.c
@@ -18,12 +18,358 @@ MODULE_VERSION("0.1");
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("Logan Gunthorpe");
 
+#define PLX_REG_DESC_RING_ADDR			0x214
+#define PLX_REG_DESC_RING_ADDR_HI		0x218
+#define PLX_REG_DESC_RING_NEXT_ADDR		0x21C
+#define PLX_REG_DESC_RING_COUNT			0x220
+#define PLX_REG_DESC_RING_LAST_ADDR		0x224
+#define PLX_REG_DESC_RING_LAST_SIZE		0x228
+#define PLX_REG_PREF_LIMIT			0x234
+#define PLX_REG_CTRL				0x238
+#define PLX_REG_CTRL2				0x23A
+#define PLX_REG_INTR_CTRL			0x23C
+#define PLX_REG_INTR_STATUS			0x23E
+
+#define PLX_REG_PREF_LIMIT_PREF_FOUR		8
+
+#define PLX_REG_CTRL_GRACEFUL_PAUSE		BIT(0)
+#define PLX_REG_CTRL_ABORT			BIT(1)
+#define PLX_REG_CTRL_WRITE_BACK_EN		BIT(2)
+#define PLX_REG_CTRL_START			BIT(3)
+#define PLX_REG_CTRL_RING_STOP_MODE		BIT(4)
+#define PLX_REG_CTRL_DESC_MODE_BLOCK		(0 << 5)
+#define PLX_REG_CTRL_DESC_MODE_ON_CHIP		(1 << 5)
+#define PLX_REG_CTRL_DESC_MODE_OFF_CHIP		(2 << 5)
+#define PLX_REG_CTRL_DESC_INVALID		BIT(8)
+#define PLX_REG_CTRL_GRACEFUL_PAUSE_DONE	BIT(9)
+#define PLX_REG_CTRL_ABORT_DONE			BIT(10)
+#define PLX_REG_CTRL_IMM_PAUSE_DONE		BIT(12)
+#define PLX_REG_CTRL_IN_PROGRESS		BIT(30)
+
+#define PLX_REG_CTRL_RESET_VAL	(PLX_REG_CTRL_DESC_INVALID | \
+				 PLX_REG_CTRL_GRACEFUL_PAUSE_DONE | \
+				 PLX_REG_CTRL_ABORT_DONE | \
+				 PLX_REG_CTRL_IMM_PAUSE_DONE)
+
+#define PLX_REG_CTRL_START_VAL	(PLX_REG_CTRL_WRITE_BACK_EN | \
+				 PLX_REG_CTRL_DESC_MODE_OFF_CHIP | \
+				 PLX_REG_CTRL_START | \
+				 PLX_REG_CTRL_RESET_VAL)
+
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_64B		0
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_128B	1
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_256B	2
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_512B	3
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_1KB		4
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_2KB		5
+#define PLX_REG_CTRL2_MAX_TXFR_SIZE_4B		7
+
+#define PLX_REG_INTR_CRTL_ERROR_EN		BIT(0)
+#define PLX_REG_INTR_CRTL_INV_DESC_EN		BIT(1)
+#define PLX_REG_INTR_CRTL_ABORT_DONE_EN		BIT(3)
+#define PLX_REG_INTR_CRTL_PAUSE_DONE_EN		BIT(4)
+#define PLX_REG_INTR_CRTL_IMM_PAUSE_DONE_EN	BIT(5)
+
+#define PLX_REG_INTR_STATUS_ERROR		BIT(0)
+#define PLX_REG_INTR_STATUS_INV_DESC		BIT(1)
+#define PLX_REG_INTR_STATUS_DESC_DONE		BIT(2)
+#define PLX_REG_INTR_CRTL_ABORT_DONE		BIT(3)
+
+struct plx_dma_hw_std_desc {
+	__le32 flags_and_size;
+	__le16 dst_addr_hi;
+	__le16 src_addr_hi;
+	__le32 dst_addr_lo;
+	__le32 src_addr_lo;
+};
+
+#define PLX_DESC_SIZE_MASK		0x7ffffff
+#define PLX_DESC_FLAG_VALID		BIT(31)
+#define PLX_DESC_FLAG_INT_WHEN_DONE	BIT(30)
+
+#define PLX_DESC_WB_SUCCESS		BIT(30)
+#define PLX_DESC_WB_RD_FAIL		BIT(29)
+#define PLX_DESC_WB_WR_FAIL		BIT(28)
+
+#define PLX_DMA_RING_COUNT		2048
+
+struct plx_dma_desc {
+	struct dma_async_tx_descriptor txd;
+	struct plx_dma_hw_std_desc *hw;
+	u32 orig_size;
+};
+
 struct plx_dma_dev {
 	struct dma_device dma_dev;
 	struct dma_chan dma_chan;
+	struct pci_dev __rcu *pdev;
 	void __iomem *bar;
+	struct tasklet_struct desc_task;
+
+	spinlock_t ring_lock;
+	bool ring_active;
+	int head;
+	int tail;
+	struct plx_dma_hw_std_desc *hw_ring;
+	dma_addr_t hw_ring_dma;
+	struct plx_dma_desc **desc_ring;
 };
 
+static struct plx_dma_dev *chan_to_plx_dma_dev(struct dma_chan *c)
+{
+	return container_of(c, struct plx_dma_dev, dma_chan);
+}
+
+static struct plx_dma_desc *plx_dma_get_desc(struct plx_dma_dev *plxdev, int i)
+{
+	return plxdev->desc_ring[i & (PLX_DMA_RING_COUNT - 1)];
+}
+
+static void plx_dma_process_desc(struct plx_dma_dev *plxdev)
+{
+	struct dmaengine_result res;
+	struct plx_dma_desc *desc;
+	u32 flags;
+
+	spin_lock_bh(&plxdev->ring_lock);
+
+	while (plxdev->tail != plxdev->head) {
+		desc = plx_dma_get_desc(plxdev, plxdev->tail);
+
+		flags = le32_to_cpu(READ_ONCE(desc->hw->flags_and_size));
+
+		if (flags & PLX_DESC_FLAG_VALID)
+			break;
+
+		res.residue = desc->orig_size - (flags & PLX_DESC_SIZE_MASK);
+
+		if (flags & PLX_DESC_WB_SUCCESS)
+			res.result = DMA_TRANS_NOERROR;
+		else if (flags & PLX_DESC_WB_WR_FAIL)
+			res.result = DMA_TRANS_WRITE_FAILED;
+		else
+			res.result = DMA_TRANS_READ_FAILED;
+
+		dma_cookie_complete(&desc->txd);
+		dma_descriptor_unmap(&desc->txd);
+		dmaengine_desc_get_callback_invoke(&desc->txd, &res);
+		desc->txd.callback = NULL;
+		desc->txd.callback_result = NULL;
+
+		plxdev->tail++;
+	}
+
+	spin_unlock_bh(&plxdev->ring_lock);
+}
+
+static void plx_dma_abort_desc(struct plx_dma_dev *plxdev)
+{
+	struct dmaengine_result res;
+	struct plx_dma_desc *desc;
+
+	plx_dma_process_desc(plxdev);
+
+	spin_lock_bh(&plxdev->ring_lock);
+
+	while (plxdev->tail != plxdev->head) {
+		desc = plx_dma_get_desc(plxdev, plxdev->tail);
+
+		res.residue = desc->orig_size;
+		res.result = DMA_TRANS_ABORTED;
+
+		dma_cookie_complete(&desc->txd);
+		dma_descriptor_unmap(&desc->txd);
+		dmaengine_desc_get_callback_invoke(&desc->txd, &res);
+		desc->txd.callback = NULL;
+		desc->txd.callback_result = NULL;
+
+		plxdev->tail++;
+	}
+
+	spin_unlock_bh(&plxdev->ring_lock);
+}
+
+static void __plx_dma_stop(struct plx_dma_dev *plxdev)
+{
+	unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+	u32 val;
+
+	val = readl(plxdev->bar + PLX_REG_CTRL);
+	if (!(val & ~PLX_REG_CTRL_GRACEFUL_PAUSE))
+		return;
+
+	writel(PLX_REG_CTRL_RESET_VAL | PLX_REG_CTRL_GRACEFUL_PAUSE,
+	       plxdev->bar + PLX_REG_CTRL);
+
+	while (!time_after(jiffies, timeout)) {
+		val = readl(plxdev->bar + PLX_REG_CTRL);
+		if (val & PLX_REG_CTRL_GRACEFUL_PAUSE_DONE)
+			break;
+
+		cpu_relax();
+	}
+
+	if (!(val & PLX_REG_CTRL_GRACEFUL_PAUSE_DONE))
+		dev_err(plxdev->dma_dev.dev,
+			"Timeout waiting for graceful pause!\n");
+
+	writel(PLX_REG_CTRL_RESET_VAL | PLX_REG_CTRL_GRACEFUL_PAUSE,
+	       plxdev->bar + PLX_REG_CTRL);
+
+	writel(0, plxdev->bar + PLX_REG_DESC_RING_COUNT);
+	writel(0, plxdev->bar + PLX_REG_DESC_RING_ADDR);
+	writel(0, plxdev->bar + PLX_REG_DESC_RING_ADDR_HI);
+	writel(0, plxdev->bar + PLX_REG_DESC_RING_NEXT_ADDR);
+}
+
+static void plx_dma_stop(struct plx_dma_dev *plxdev)
+{
+	rcu_read_lock();
+	if (!rcu_dereference(plxdev->pdev)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	__plx_dma_stop(plxdev);
+
+	rcu_read_unlock();
+}
+
+static void plx_dma_desc_task(unsigned long data)
+{
+	struct plx_dma_dev *plxdev = (void *)data;
+
+	plx_dma_process_desc(plxdev);
+}
+
+static irqreturn_t plx_dma_isr(int irq, void *devid)
+{
+	struct plx_dma_dev *plxdev = devid;
+	u32 status;
+
+	status = readw(plxdev->bar + PLX_REG_INTR_STATUS);
+
+	if (!status)
+		return IRQ_NONE;
+
+	if (status & PLX_REG_INTR_STATUS_DESC_DONE && plxdev->ring_active)
+		tasklet_schedule(&plxdev->desc_task);
+
+	writew(status, plxdev->bar + PLX_REG_INTR_STATUS);
+
+	return IRQ_HANDLED;
+}
+
+static int plx_dma_alloc_desc(struct plx_dma_dev *plxdev)
+{
+	struct plx_dma_desc *desc;
+	int i;
+
+	plxdev->desc_ring = kcalloc(PLX_DMA_RING_COUNT,
+				    sizeof(*plxdev->desc_ring), GFP_KERNEL);
+	if (!plxdev->desc_ring)
+		return -ENOMEM;
+
+	for (i = 0; i < PLX_DMA_RING_COUNT; i++) {
+		desc = kzalloc(sizeof(*desc), GFP_KERNEL);
+		if (!desc)
+			goto free_and_exit;
+
+		dma_async_tx_descriptor_init(&desc->txd, &plxdev->dma_chan);
+		desc->hw = &plxdev->hw_ring[i];
+		plxdev->desc_ring[i] = desc;
+	}
+
+	return 0;
+
+free_and_exit:
+	for (i = 0; i < PLX_DMA_RING_COUNT; i++)
+		kfree(plxdev->desc_ring[i]);
+	kfree(plxdev->desc_ring);
+	return -ENOMEM;
+}
+
+static int plx_dma_alloc_chan_resources(struct dma_chan *chan)
+{
+	struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(chan);
+	size_t ring_sz = PLX_DMA_RING_COUNT * sizeof(*plxdev->hw_ring);
+	int rc;
+
+	plxdev->head = plxdev->tail = 0;
+	plxdev->hw_ring = dma_alloc_coherent(plxdev->dma_dev.dev, ring_sz,
+					     &plxdev->hw_ring_dma, GFP_KERNEL);
+	if (!plxdev->hw_ring)
+		return -ENOMEM;
+
+	rc = plx_dma_alloc_desc(plxdev);
+	if (rc)
+		goto out_free_hw_ring;
+
+	rcu_read_lock();
+	if (!rcu_dereference(plxdev->pdev)) {
+		rcu_read_unlock();
+		rc = -ENODEV;
+		goto out_free_hw_ring;
+	}
+
+	writel(PLX_REG_CTRL_RESET_VAL, plxdev->bar + PLX_REG_CTRL);
+	writel(lower_32_bits(plxdev->hw_ring_dma),
+	       plxdev->bar + PLX_REG_DESC_RING_ADDR);
+	writel(upper_32_bits(plxdev->hw_ring_dma),
+	       plxdev->bar + PLX_REG_DESC_RING_ADDR_HI);
+	writel(lower_32_bits(plxdev->hw_ring_dma),
+	       plxdev->bar + PLX_REG_DESC_RING_NEXT_ADDR);
+	writel(PLX_DMA_RING_COUNT, plxdev->bar + PLX_REG_DESC_RING_COUNT);
+	writel(PLX_REG_PREF_LIMIT_PREF_FOUR, plxdev->bar + PLX_REG_PREF_LIMIT);
+
+	plxdev->ring_active = true;
+
+	rcu_read_unlock();
+
+	return PLX_DMA_RING_COUNT;
+
+out_free_hw_ring:
+	dma_free_coherent(plxdev->dma_dev.dev, ring_sz, plxdev->hw_ring,
+			  plxdev->hw_ring_dma);
+	return rc;
+}
+
+static void plx_dma_free_chan_resources(struct dma_chan *chan)
+{
+	struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(chan);
+	size_t ring_sz = PLX_DMA_RING_COUNT * sizeof(*plxdev->hw_ring);
+	struct pci_dev *pdev;
+	int irq = -1;
+	int i;
+
+	spin_lock_bh(&plxdev->ring_lock);
+	plxdev->ring_active = false;
+	spin_unlock_bh(&plxdev->ring_lock);
+
+	plx_dma_stop(plxdev);
+
+	rcu_read_lock();
+	pdev = rcu_dereference(plxdev->pdev);
+	if (pdev)
+		irq = pci_irq_vector(pdev, 0);
+	rcu_read_unlock();
+
+	if (irq > 0)
+		synchronize_irq(irq);
+
+	tasklet_kill(&plxdev->desc_task);
+
+	plx_dma_abort_desc(plxdev);
+
+	for (i = 0; i < PLX_DMA_RING_COUNT; i++)
+		kfree(plxdev->desc_ring[i]);
+
+	kfree(plxdev->desc_ring);
+	dma_free_coherent(plxdev->dma_dev.dev, ring_sz, plxdev->hw_ring,
+			  plxdev->hw_ring_dma);
+
+}
+
 static void plx_dma_release(struct dma_device *dma_dev)
 {
 	struct plx_dma_dev *plxdev =
@@ -44,6 +390,18 @@ static int plx_dma_create(struct pci_dev *pdev)
 	if (!plxdev)
 		return -ENOMEM;
 
+	rc = request_irq(pci_irq_vector(pdev, 0), plx_dma_isr, 0,
+			 KBUILD_MODNAME, plxdev);
+	if (rc) {
+		kfree(plxdev);
+		return rc;
+	}
+
+	spin_lock_init(&plxdev->ring_lock);
+	tasklet_init(&plxdev->desc_task, plx_dma_desc_task,
+		     (unsigned long)plxdev);
+
+	RCU_INIT_POINTER(plxdev->pdev, pdev);
 	plxdev->bar = pcim_iomap_table(pdev)[0];
 
 	dma = &plxdev->dma_dev;
@@ -52,6 +410,8 @@ static int plx_dma_create(struct pci_dev *pdev)
 	dma->copy_align = DMAENGINE_ALIGN_1_BYTE;
 	dma->dev = get_device(&pdev->dev);
 
+	dma->device_alloc_chan_resources = plx_dma_alloc_chan_resources;
+	dma->device_free_chan_resources = plx_dma_free_chan_resources;
 	dma->device_release = plx_dma_release;
 
 	chan = &plxdev->dma_chan;
@@ -122,6 +482,16 @@ static void plx_dma_remove(struct pci_dev *pdev)
 
 	free_irq(pci_irq_vector(pdev, 0),  plxdev);
 
+	rcu_assign_pointer(plxdev->pdev, NULL);
+	synchronize_rcu();
+
+	spin_lock_bh(&plxdev->ring_lock);
+	plxdev->ring_active = false;
+	spin_unlock_bh(&plxdev->ring_lock);
+
+	__plx_dma_stop(plxdev);
+	plx_dma_abort_desc(plxdev);
+
 	plxdev->bar = NULL;
 	dma_async_device_unregister(&plxdev->dma_dev);
 
-- 
2.20.1

[PATCH v3 3/3] dmaengine: plx-dma: Implement descriptor submission

[Logan Gunthorpe]

On prep, a spin lock is taken and the next entry in the circular buffer
is filled. On submit, the valid bit is set in the hardware descriptor
and the lock is released.

The DMA engine is started (if it's not already running) when the client
calls dma_async_issue_pending().

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 drivers/dma/plx_dma.c | 119 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)

diff --git a/drivers/dma/plx_dma.c b/drivers/dma/plx_dma.c
index f3a5c9e47658..db4c5fd453a9 100644
--- a/drivers/dma/plx_dma.c
+++ b/drivers/dma/plx_dma.c
@@ -7,6 +7,7 @@
 
 #include "dmaengine.h"
 
+#include <linux/circ_buf.h>
 #include <linux/dmaengine.h>
 #include <linux/kref.h>
 #include <linux/list.h>
@@ -120,6 +121,11 @@ static struct plx_dma_dev *chan_to_plx_dma_dev(struct dma_chan *c)
 	return container_of(c, struct plx_dma_dev, dma_chan);
 }
 
+static struct plx_dma_desc *to_plx_desc(struct dma_async_tx_descriptor *txd)
+{
+	return container_of(txd, struct plx_dma_desc, txd);
+}
+
 static struct plx_dma_desc *plx_dma_get_desc(struct plx_dma_dev *plxdev, int i)
 {
 	return plxdev->desc_ring[i & (PLX_DMA_RING_COUNT - 1)];
@@ -242,6 +248,113 @@ static void plx_dma_desc_task(unsigned long data)
 	plx_dma_process_desc(plxdev);
 }
 
+static struct dma_async_tx_descriptor *plx_dma_prep_memcpy(struct dma_chan *c,
+		dma_addr_t dma_dst, dma_addr_t dma_src, size_t len,
+		unsigned long flags)
+	__acquires(plxdev->ring_lock)
+{
+	struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(c);
+	struct plx_dma_desc *plxdesc;
+
+	spin_lock_bh(&plxdev->ring_lock);
+	if (!plxdev->ring_active)
+		goto err_unlock;
+
+	if (!CIRC_SPACE(plxdev->head, plxdev->tail, PLX_DMA_RING_COUNT))
+		goto err_unlock;
+
+	if (len > PLX_DESC_SIZE_MASK)
+		goto err_unlock;
+
+	plxdesc = plx_dma_get_desc(plxdev, plxdev->head);
+	plxdev->head++;
+
+	plxdesc->hw->dst_addr_lo = cpu_to_le32(lower_32_bits(dma_dst));
+	plxdesc->hw->dst_addr_hi = cpu_to_le16(upper_32_bits(dma_dst));
+	plxdesc->hw->src_addr_lo = cpu_to_le32(lower_32_bits(dma_src));
+	plxdesc->hw->src_addr_hi = cpu_to_le16(upper_32_bits(dma_src));
+
+	plxdesc->orig_size = len;
+
+	if (flags & DMA_PREP_INTERRUPT)
+		len |= PLX_DESC_FLAG_INT_WHEN_DONE;
+
+	plxdesc->hw->flags_and_size = cpu_to_le32(len);
+	plxdesc->txd.flags = flags;
+
+	/* return with the lock held, it will be released in tx_submit */
+
+	return &plxdesc->txd;
+
+err_unlock:
+	/*
+	 * Keep sparse happy by restoring an even lock count on
+	 * this lock.
+	 */
+	__acquire(plxdev->ring_lock);
+
+	spin_unlock_bh(&plxdev->ring_lock);
+	return NULL;
+}
+
+static dma_cookie_t plx_dma_tx_submit(struct dma_async_tx_descriptor *desc)
+	__releases(plxdev->ring_lock)
+{
+	struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(desc->chan);
+	struct plx_dma_desc *plxdesc = to_plx_desc(desc);
+	dma_cookie_t cookie;
+
+	cookie = dma_cookie_assign(desc);
+
+	/*
+	 * Ensure the descriptor updates are visible to the dma device
+	 * before setting the valid bit.
+	 */
+	wmb();
+
+	plxdesc->hw->flags_and_size |= cpu_to_le32(PLX_DESC_FLAG_VALID);
+
+	spin_unlock_bh(&plxdev->ring_lock);
+
+	return cookie;
+}
+
+static enum dma_status plx_dma_tx_status(struct dma_chan *chan,
+		dma_cookie_t cookie, struct dma_tx_state *txstate)
+{
+	struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(chan);
+	enum dma_status ret;
+
+	ret = dma_cookie_status(chan, cookie, txstate);
+	if (ret == DMA_COMPLETE)
+		return ret;
+
+	plx_dma_process_desc(plxdev);
+
+	return dma_cookie_status(chan, cookie, txstate);
+}
+
+static void plx_dma_issue_pending(struct dma_chan *chan)
+{
+	struct plx_dma_dev *plxdev = chan_to_plx_dma_dev(chan);
+
+	rcu_read_lock();
+	if (!rcu_dereference(plxdev->pdev)) {
+		rcu_read_unlock();
+		return;
+	}
+
+	/*
+	 * Ensure the valid bits are visible before starting the
+	 * DMA engine.
+	 */
+	wmb();
+
+	writew(PLX_REG_CTRL_START_VAL, plxdev->bar + PLX_REG_CTRL);
+
+	rcu_read_unlock();
+}
+
 static irqreturn_t plx_dma_isr(int irq, void *devid)
 {
 	struct plx_dma_dev *plxdev = devid;
@@ -276,7 +389,9 @@ static int plx_dma_alloc_desc(struct plx_dma_dev *plxdev)
 			goto free_and_exit;
 
 		dma_async_tx_descriptor_init(&desc->txd, &plxdev->dma_chan);
+		desc->txd.tx_submit = plx_dma_tx_submit;
 		desc->hw = &plxdev->hw_ring[i];
+
 		plxdev->desc_ring[i] = desc;
 	}
 
@@ -407,11 +522,15 @@ static int plx_dma_create(struct pci_dev *pdev)
 	dma = &plxdev->dma_dev;
 	dma->chancnt = 1;
 	INIT_LIST_HEAD(&dma->channels);
+	dma_cap_set(DMA_MEMCPY, dma->cap_mask);
 	dma->copy_align = DMAENGINE_ALIGN_1_BYTE;
 	dma->dev = get_device(&pdev->dev);
 
 	dma->device_alloc_chan_resources = plx_dma_alloc_chan_resources;
 	dma->device_free_chan_resources = plx_dma_free_chan_resources;
+	dma->device_prep_dma_memcpy = plx_dma_prep_memcpy;
+	dma->device_issue_pending = plx_dma_issue_pending;
+	dma->device_tx_status = plx_dma_tx_status;
 	dma->device_release = plx_dma_release;
 
 	chan = &plxdev->dma_chan;
-- 
2.20.1

Re: [PATCH v3 0/3] PLX Switch DMA Engine Driver

[Vinod Koul]

On 03-01-20, 14:20, Logan Gunthorpe wrote:
> This is v3 of the patchset. The in-use unbind bits have been sent and
> accepted as a separate patch set. This patchset just includes the new
> driver which has been updated to use the common reference counting.
> 
> This patchset is based off of vkoul/slave-dma.git/next and a git branch is
> available here:
> 
> https://github.com/sbates130272/linux-p2pmem/ plx-dma-v3

Applied all, thanks, apologies for delay!

-- 
~Vinod