[PATCH 13/15] dmaengine: dw-edma: Add auxiliary-bus frontend for exported eDMA

[Koichiro Den]

Add a small auxiliary-bus frontend that binds to the DMA child created
by ntb_hw_epf when a peer advertises exported DMA ABI v1.

The frontend reads the ABI header from the exported BAR slice, wires the
controller register window and per-channel descriptor windows into a
struct dw_edma_chip, and then calls into the common dw-edma core.

Use the parent PCI device as chip->dev so IRQ lookup and MSI message
composition continue to use the vectors owned by the NTB PCI function.
Default delegated channels to remote interrupt delivery.

Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
 drivers/dma/dw-edma/Kconfig       |  11 ++
 drivers/dma/dw-edma/Makefile      |   1 +
 drivers/dma/dw-edma/dw-edma-aux.c | 297 ++++++++++++++++++++++++++++++
 3 files changed, 309 insertions(+)
 create mode 100644 drivers/dma/dw-edma/dw-edma-aux.c

diff --git a/drivers/dma/dw-edma/Kconfig b/drivers/dma/dw-edma/Kconfig
index 2b6f2679508d..a31f6bd784c2 100644
--- a/drivers/dma/dw-edma/Kconfig
+++ b/drivers/dma/dw-edma/Kconfig
@@ -19,4 +19,15 @@ config DW_EDMA_PCIE
 	  eDMA controller and an endpoint PCIe device. This also serves
 	  as a reference design to whom desires to use this IP.
 
+config DW_EDMA_AUX
+	tristate "Synopsys DesignWare eDMA auxiliary-bus frontend"
+	depends on AUXILIARY_BUS
+	help
+	  Build a frontend for an endpoint-integrated Synopsys
+	  DesignWare eDMA controller discovered through an auxiliary
+	  device, such as the child created by ntb_hw_epf for an
+	  endpoint DMA engine exported through vNTB. The driver maps the
+	  exported control and descriptor windows and registers the
+	  remote engine with DMAEngine.
+
 endif # DW_EDMA
diff --git a/drivers/dma/dw-edma/Makefile b/drivers/dma/dw-edma/Makefile
index 83ab58f87760..2545ce4a1989 100644
--- a/drivers/dma/dw-edma/Makefile
+++ b/drivers/dma/dw-edma/Makefile
@@ -7,3 +7,4 @@ dw-edma-objs			:= dw-edma-core.o	\
 				   dw-edma-v0-core.o	\
 				   dw-hdma-v0-core.o $(dw-edma-y)
 obj-$(CONFIG_DW_EDMA_PCIE)	+= dw-edma-pcie.o
+obj-$(CONFIG_DW_EDMA_AUX)	+= dw-edma-aux.o
diff --git a/drivers/dma/dw-edma/dw-edma-aux.c b/drivers/dma/dw-edma/dw-edma-aux.c
new file mode 100644
index 000000000000..a7481fa289d0
--- /dev/null
+++ b/drivers/dma/dw-edma/dw-edma-aux.c
@@ -0,0 +1,297 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Synopsys DesignWare eDMA auxiliary-bus frontend
+ */
+
+#include <linux/auxiliary_bus.h>
+#include <linux/device.h>
+#include <linux/dma/edma.h>
+#include <linux/list.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/pci-ep-dma.h>
+#include <linux/property.h>
+
+struct dw_edma_aux {
+	struct list_head node;
+	struct pci_dev *pdev;
+	struct dw_edma_chip chip;
+	void __iomem *bar_base;
+	void __iomem *ctrl_base;
+	u32 irq_base;
+};
+
+static DEFINE_MUTEX(dw_edma_aux_lock);
+static LIST_HEAD(dw_edma_aux_list);
+
+static struct dw_edma_aux *dw_edma_aux_find_by_pdev(struct pci_dev *pdev)
+{
+	struct dw_edma_aux *aux;
+
+	list_for_each_entry(aux, &dw_edma_aux_list, node)
+		if (aux->pdev == pdev)
+			return aux;
+
+	return NULL;
+}
+
+static int dw_edma_aux_register(struct dw_edma_aux *aux)
+{
+	int ret = 0;
+
+	mutex_lock(&dw_edma_aux_lock);
+	if (dw_edma_aux_find_by_pdev(aux->pdev))
+		ret = -EEXIST;
+	else
+		list_add_tail(&aux->node, &dw_edma_aux_list);
+	mutex_unlock(&dw_edma_aux_lock);
+
+	return ret;
+}
+
+static void dw_edma_aux_unregister(struct dw_edma_aux *aux)
+{
+	mutex_lock(&dw_edma_aux_lock);
+	if (!list_empty(&aux->node))
+		list_del_init(&aux->node);
+	mutex_unlock(&dw_edma_aux_lock);
+}
+
+static bool dw_edma_aux_region_valid(u32 dma_off, u32 dma_sz, u32 off, u32 sz)
+{
+	u32 rel;
+
+	if (off < dma_off || !sz)
+		return false;
+
+	rel = off - dma_off;
+	if (rel > dma_sz)
+		return false;
+
+	return sz <= dma_sz - rel;
+}
+
+static int dw_edma_aux_irq_vector(struct device *dev, unsigned int nr)
+{
+	struct dw_edma_aux *aux;
+	int irq = -ENODEV;
+
+	mutex_lock(&dw_edma_aux_lock);
+	aux = dw_edma_aux_find_by_pdev(to_pci_dev(dev));
+	if (aux)
+		irq = pci_irq_vector(aux->pdev, aux->irq_base + nr);
+	mutex_unlock(&dw_edma_aux_lock);
+
+	return irq;
+}
+
+static const struct dw_edma_plat_ops dw_edma_aux_plat_ops = {
+	.irq_vector = dw_edma_aux_irq_vector,
+};
+
+static int dw_edma_aux_probe(struct auxiliary_device *auxdev,
+			     const struct auxiliary_device_id *id)
+{
+	void __iomem *base, *ctrl_base = NULL, *reg_base = NULL;
+	struct device *dev = &auxdev->dev;
+	struct pci_dev *pdev = to_pci_dev(dev->parent);
+	struct pci_ep_dma_hdr_v1 hdr;
+	struct dw_edma_chip *chip;
+	struct dw_edma_aux *aux;
+	u32 dma_abi, dma_bar, dma_offset, dma_size;
+	u32 desc_bar, desc_offset, desc_size;
+	u32 ctrl_bar, ctrl_offset, ctrl_size;
+	u32 irq_base, irq_count, num_chans;
+	u16 hdr_size, total_size;
+	u32 hdr_irq_count;
+	unsigned int i;
+	int ret;
+
+	ret = device_property_read_u32(dev, "dma-abi", &dma_abi);
+	if (ret)
+		return ret;
+	if (dma_abi != PCI_EP_DMA_ABI_V1)
+		return -EINVAL;
+
+	ret = device_property_read_u32(dev, "dma-bar", &dma_bar);
+	if (ret)
+		return ret;
+	ret = device_property_read_u32(dev, "dma-offset", &dma_offset);
+	if (ret)
+		return ret;
+	ret = device_property_read_u32(dev, "dma-size", &dma_size);
+	if (ret)
+		return ret;
+	if (dma_bar > BAR_5 || !dma_size)
+		return -EINVAL;
+	if (dma_size < sizeof(hdr))
+		return -EINVAL;
+	ret = device_property_read_u32(dev, "dma-irq-base", &irq_base);
+	if (ret)
+		return ret;
+	ret = device_property_read_u32(dev, "dma-irq-count", &irq_count);
+	if (ret)
+		return ret;
+	if (!irq_count)
+		return -EINVAL;
+
+	base = pci_iomap_range(pdev, dma_bar, dma_offset, dma_size);
+	if (!base)
+		return -ENOMEM;
+
+	memcpy_fromio(&hdr, base, sizeof(hdr));
+	if (le32_to_cpu(hdr.magic) != PCI_EP_DMA_MAGIC) {
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+	if (le16_to_cpu(hdr.version) != 1) {
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+
+	hdr_size = le16_to_cpu(hdr.hdr_size);
+	total_size = le32_to_cpu(hdr.total_size);
+	hdr_irq_count = le32_to_cpu(hdr.irq_count);
+	if (hdr_size != sizeof(hdr) || total_size != dma_size ||
+	    hdr_irq_count != irq_count) {
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+
+	ctrl_bar = le32_to_cpu(hdr.ctrl_bar);
+	ctrl_offset = le32_to_cpu(hdr.ctrl_offset);
+	ctrl_size = le32_to_cpu(hdr.ctrl_size);
+	num_chans = le32_to_cpu(hdr.num_chans);
+	if (!num_chans || num_chans > PCI_EP_DMA_MAX_CHANS ||
+	    num_chans > irq_count) {
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+
+	if (!ctrl_size || ctrl_bar > BAR_5) {
+		ret = -EINVAL;
+		goto err_iounmap;
+	}
+
+	/*
+	 * The exported DMA window is only guaranteed to cover the locator and
+	 * descriptor subranges. The live eDMA register block may be advertised
+	 * through another BAR, or elsewhere in the same BAR, and must then be
+	 * mapped directly.
+	 */
+	if (ctrl_bar == dma_bar &&
+	    dw_edma_aux_region_valid(dma_offset, dma_size, ctrl_offset,
+				     ctrl_size)) {
+		ctrl_base = NULL;
+		reg_base = base + (ctrl_offset - dma_offset);
+	} else {
+		ctrl_base = pci_iomap_range(pdev, ctrl_bar, ctrl_offset,
+					    ctrl_size);
+		if (!ctrl_base) {
+			ret = -ENOMEM;
+			goto err_iounmap;
+		}
+		reg_base = ctrl_base;
+	}
+
+	for (i = 0; i < num_chans; i++) {
+		desc_bar = le32_to_cpu(hdr.chans[i].desc_bar);
+		desc_offset = le32_to_cpu(hdr.chans[i].desc_offset);
+		desc_size = le32_to_cpu(hdr.chans[i].desc_size);
+		if (desc_bar != dma_bar ||
+		    !dw_edma_aux_region_valid(dma_offset, dma_size, desc_offset,
+					 desc_size)) {
+			ret = -EINVAL;
+			goto err_ctrl_iounmap;
+		}
+	}
+
+	aux = devm_kzalloc(dev, sizeof(*aux), GFP_KERNEL);
+	if (!aux) {
+		ret = -ENOMEM;
+		goto err_ctrl_iounmap;
+	}
+
+	INIT_LIST_HEAD(&aux->node);
+	aux->pdev = pdev;
+	aux->bar_base = base;
+	aux->ctrl_base = ctrl_base;
+	aux->irq_base = irq_base;
+
+	ret = dw_edma_aux_register(aux);
+	if (ret)
+		goto err_ctrl_iounmap;
+
+	chip = &aux->chip;
+	chip->dev = dev->parent;
+	chip->nr_irqs = irq_count;
+	chip->ops = &dw_edma_aux_plat_ops;
+	chip->flags = 0;
+	chip->mf = EDMA_MF_EDMA_UNROLL;
+	chip->default_irq_mode = DW_EDMA_CH_IRQ_REMOTE;
+	chip->reg_base = reg_base;
+	chip->ll_wr_cnt = 0;
+	/*
+	 * ABI v1 exports READ channels only. @hdr->chans[] is defined as a dense
+	 * prefix of the remote hardware READ-channel space, ordered by remote
+	 * hardware READ-channel index starting at 0, so ll_region_rd[i] can be
+	 * consumed as local READ channel i.
+	 */
+	chip->ll_rd_cnt = num_chans;
+	for (i = 0; i < num_chans; i++) {
+		desc_offset = le32_to_cpu(hdr.chans[i].desc_offset);
+		desc_size = le32_to_cpu(hdr.chans[i].desc_size);
+		chip->ll_region_rd[i].vaddr.io = base + (desc_offset - dma_offset);
+		chip->ll_region_rd[i].paddr = le64_to_cpu(hdr.chans[i].desc_phys_addr);
+		chip->ll_region_rd[i].sz = desc_size;
+	}
+
+	dev_set_drvdata(dev, aux);
+	ret = dw_edma_probe(chip);
+	if (ret) {
+		dw_edma_aux_unregister(aux);
+		goto err_ctrl_iounmap;
+	}
+
+	return 0;
+
+err_ctrl_iounmap:
+	if (ctrl_base)
+		pci_iounmap(pdev, ctrl_base);
+err_iounmap:
+	pci_iounmap(pdev, base);
+	return ret;
+}
+
+static void dw_edma_aux_remove(struct auxiliary_device *auxdev)
+{
+	struct dw_edma_aux *aux = dev_get_drvdata(&auxdev->dev);
+
+	if (!aux)
+		return;
+
+	dw_edma_remove(&aux->chip);
+	dw_edma_aux_unregister(aux);
+	if (aux->ctrl_base)
+		pci_iounmap(aux->pdev, aux->ctrl_base);
+	pci_iounmap(aux->pdev, aux->bar_base);
+}
+
+static const struct auxiliary_device_id dw_edma_aux_ids[] = {
+	{ .name = "ntb_hw_epf.ep_dma_v1" },
+	{ }
+};
+MODULE_DEVICE_TABLE(auxiliary, dw_edma_aux_ids);
+
+static struct auxiliary_driver dw_edma_aux_driver = {
+	.name = "dw_edma_aux",
+	.probe = dw_edma_aux_probe,
+	.remove = dw_edma_aux_remove,
+	.id_table = dw_edma_aux_ids,
+};
+module_auxiliary_driver(dw_edma_aux_driver);
+
+MODULE_DESCRIPTION("Synopsys DesignWare eDMA auxiliary-bus frontend");
+MODULE_AUTHOR("Koichiro Den <den@xxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL");
-- 
2.51.0