linux-kernel - [PATCH 4/4] of: Add plumbing for bounced DMA pool

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Date:   Mon, 13 Jul 2020 17:12:11 +0800
From:   Claire Chang <tientzu@...omium.org>
To:     robh+dt@...nel.org, frowand.list@...il.com, hch@....de,
        m.szyprowski@...sung.com, robin.murphy@....com
Cc:     treding@...dia.com, gregkh@...uxfoundation.org,
        saravanak@...gle.com, suzuki.poulose@....com,
        dan.j.williams@...el.com, heikki.krogerus@...ux.intel.com,
        bgolaszewski@...libre.com, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        tfiga@...omium.org, drinkcat@...omium.org,
        Claire Chang <tientzu@...omium.org>
Subject: [PATCH 4/4] of: Add plumbing for bounced DMA pool

If a device is not behind an IOMMU, we look up the device node and set
up the bounced DMA when the bounced-dma property is presented. One can
specify two reserved-memory nodes in the device tree. One with
shared-dma-pool to handle the coherent DMA buffer allocation, and
another one with bounced-dma-pool for regular DMA to/from system memory,
which would be subject to bouncing.

Signed-off-by: Claire Chang <tientzu@...omium.org>
---
 drivers/of/address.c    | 37 +++++++++++++++++++++++++++++++++++++
 drivers/of/device.c     |  3 +++
 drivers/of/of_private.h |  6 ++++++
 3 files changed, 46 insertions(+)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 8eea3f6e29a4..a767b80f8862 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -8,6 +8,7 @@
 #include <linux/logic_pio.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
+#include <linux/of_reserved_mem.h>
 #include <linux/pci.h>
 #include <linux/pci_regs.h>
 #include <linux/sizes.h>
@@ -1009,6 +1010,42 @@ int of_dma_get_range(struct device_node *np, u64 *dma_addr, u64 *paddr, u64 *siz
 	return ret;
 }
 
+int of_dma_set_bounce_buffer(struct device *dev)
+{
+	int length, size, ret, i;
+	u32 idx[2];
+
+	if (!dev || !dev->of_node)
+		return -EINVAL;
+
+	if (!of_get_property(dev->of_node, "bounced-dma", &length))
+		return 0;
+
+	size = length / sizeof(idx[0]);
+	if (size > ARRAY_SIZE(idx)) {
+		dev_err(dev,
+			"bounced-dma expected less than or equal to 2 indexs, but got %d\n",
+			size);
+		return -EINVAL;
+	}
+
+	ret = of_property_read_u32_array(dev->of_node, "bounced-dma", idx,
+					 size);
+
+	for (i = 0; i < size; i++) {
+		ret = of_reserved_mem_device_init_by_idx(dev, dev->of_node,
+							 idx[i]);
+		if (ret) {
+			dev_err(dev,
+				"of_reserved_mem_device_init_by_idx() failed with %d\n",
+				ret);
+			return ret;
+		}
+	}
+
+	return 0;
+}
+
 /**
  * of_dma_is_coherent - Check if device is coherent
  * @np:	device node
diff --git a/drivers/of/device.c b/drivers/of/device.c
index 27203bfd0b22..238beef48a50 100644
--- a/drivers/of/device.c
+++ b/drivers/of/device.c
@@ -169,6 +169,9 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma)
 
 	arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent);
 
+	if (!iommu)
+		return of_dma_set_bounce_buffer(dev);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(of_dma_configure);
diff --git a/drivers/of/of_private.h b/drivers/of/of_private.h
index edc682249c00..3d1b8cca1519 100644
--- a/drivers/of/of_private.h
+++ b/drivers/of/of_private.h
@@ -160,12 +160,18 @@ extern int of_bus_n_size_cells(struct device_node *np);
 #ifdef CONFIG_OF_ADDRESS
 extern int of_dma_get_range(struct device_node *np, u64 *dma_addr,
 			    u64 *paddr, u64 *size);
+extern int of_dma_set_bounce_buffer(struct device *dev);
 #else
 static inline int of_dma_get_range(struct device_node *np, u64 *dma_addr,
 				   u64 *paddr, u64 *size)
 {
 	return -ENODEV;
 }
+
+static inline int of_dma_get_bounce_buffer(struct device *dev)
+{
+	return -ENODEV;
+}
 #endif
 
 #endif /* _LINUX_OF_PRIVATE_H */
-- 
2.27.0.383.g050319c2ae-goog