[PATCH 1/4] i3c: master: Add helpers for DMA mapping and bounce buffer handling

* [PATCH 1/4] i3c: master: Add helpers for DMA mapping and bounce buffer handling
@ 2025-07-31 14:14 Jarkko Nikula
  2025-07-31 14:14 ` [PATCH 2/4] i3c: mipi-i3c-hci: Use core helpers for DMA mapping and bounce buffering Jarkko Nikula
                   ` (3 more replies)
  0 siblings, 4 replies; 11+ messages in thread
From: Jarkko Nikula @ 2025-07-31 14:14 UTC (permalink / raw)
  To: linux-i3c; +Cc: Alexandre Belloni, Frank Li, Jarkko Nikula

Add helpers for I3C host controller drivers for DMA mapping/unmapping
and bounce buffer handling. A bounce buffer is allocated if the buffer
is not DMA'able or when the driver requires it for a transfer.

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
---
 drivers/i3c/master.c       | 74 ++++++++++++++++++++++++++++++++++++++
 include/linux/i3c/master.h | 20 +++++++++++
 2 files changed, 94 insertions(+)

diff --git a/drivers/i3c/master.c b/drivers/i3c/master.c
index 2ef898a8fd80..a1daf18ea707 100644
--- a/drivers/i3c/master.c
+++ b/drivers/i3c/master.c
@@ -8,6 +8,7 @@
 #include <linux/atomic.h>
 #include <linux/bug.h>
 #include <linux/device.h>
+#include <linux/dma-mapping.h>
 #include <linux/err.h>
 #include <linux/export.h>
 #include <linux/kernel.h>
@@ -1727,6 +1728,79 @@ int i3c_master_do_daa(struct i3c_master_controller *master)
 }
 EXPORT_SYMBOL_GPL(i3c_master_do_daa);
 
+/**
+ * i3c_master_dma_map_single() - Map buffer for single DMA transfer
+ * @dev: device object of a device doing DMA
+ * @buf: destination/source buffer for DMA
+ * @len: length of transfer
+ * @need_bounce: true if buffer is not DMA safe and need a bounce buffer
+ * @dir: DMA direction
+ *
+ * Map buffer for a DMA transfer and allocate a bounce buffer if required.
+ *
+ * Return: I3C DMA transfer descriptor or NULL in case of error.
+ */
+struct i3c_dma *i3c_master_dma_map_single(struct device *dev, void *buf,
+	size_t len, bool need_bounce, enum dma_data_direction dir)
+{
+	struct i3c_dma *dma_xfer;
+	void *dma_buf = buf;
+
+	dma_xfer = kzalloc(sizeof(*dma_xfer), GFP_KERNEL);
+	if (!dma_xfer)
+		return NULL;
+
+	dma_xfer->buf = buf;
+	dma_xfer->dir = dir;
+	dma_xfer->len = len;
+	if (is_vmalloc_addr(buf))
+		need_bounce = true;
+
+	if (need_bounce) {
+		if (dir == DMA_FROM_DEVICE)
+			dma_buf = kzalloc(ALIGN(len, cache_line_size()),
+						GFP_KERNEL);
+		else
+			dma_buf = kmemdup(buf, len, GFP_KERNEL);
+		if (!dma_buf)
+			goto err_alloc;
+
+		dma_xfer->bounce_buf = dma_buf;
+	}
+
+	dma_xfer->addr = dma_map_single(dev, dma_buf, len, dir);
+	if (dma_mapping_error(dev, dma_xfer->addr))
+		goto err_map;
+
+	return dma_xfer;
+err_map:
+	kfree(dma_xfer->bounce_buf);
+err_alloc:
+	kfree(dma_xfer);
+	return NULL;
+}
+EXPORT_SYMBOL_GPL(i3c_master_dma_map_single);
+
+/**
+ * i3c_master_dma_unmap_single() - Unmap buffer after DMA
+ * @dev: device object of a device doing DMA
+ * @dma_xfer: DMA transfer and mapping descriptor
+ *
+ * Unmap buffer and cleanup DMA transfer descriptor.
+ */
+void i3c_master_dma_unmap_single(struct device *dev, struct i3c_dma *dma_xfer)
+{
+	dma_unmap_single(dev, dma_xfer->addr, dma_xfer->len, dma_xfer->dir);
+	if (dma_xfer->bounce_buf) {
+		if (dma_xfer->dir == DMA_FROM_DEVICE)
+			memcpy(dma_xfer->buf, dma_xfer->bounce_buf,
+			       dma_xfer->len);
+		kfree(dma_xfer->bounce_buf);
+	}
+	kfree(dma_xfer);
+}
+EXPORT_SYMBOL_GPL(i3c_master_dma_unmap_single);
+
 /**
  * i3c_master_set_info() - set master device information
  * @master: master used to send frames on the bus
diff --git a/include/linux/i3c/master.h b/include/linux/i3c/master.h
index 043f5c7ff398..e39350b1038e 100644
--- a/include/linux/i3c/master.h
+++ b/include/linux/i3c/master.h
@@ -558,6 +558,22 @@ struct i3c_master_controller {
 #define i3c_bus_for_each_i3cdev(bus, dev)				\
 	list_for_each_entry(dev, &(bus)->devs.i3c, common.node)
 
+/**
+ * struct i3c_dma - DMA transfer and mapping descriptor
+ * @buf: destination/source buffer for DMA
+ * @len: length of transfer
+ * @addr: mapped DMA address for a Host Controller Driver
+ * @dir: DMA direction
+ * @bounce_buf: an allocated bounce buffer if transfer needs it or NULL
+ */
+struct i3c_dma {
+	void *buf;
+	size_t len;
+	dma_addr_t addr;
+	enum dma_data_direction dir;
+	void *bounce_buf;
+};
+
 int i3c_master_do_i2c_xfers(struct i3c_master_controller *master,
 			    const struct i2c_msg *xfers,
 			    int nxfers);
@@ -575,6 +591,10 @@ int i3c_master_get_free_addr(struct i3c_master_controller *master,
 int i3c_master_add_i3c_dev_locked(struct i3c_master_controller *master,
 				  u8 addr);
 int i3c_master_do_daa(struct i3c_master_controller *master);
+struct i3c_dma *i3c_master_dma_map_single(struct device *dev, void *ptr,
+					  size_t len, bool dma_safe,
+					  enum dma_data_direction dir);
+void i3c_master_dma_unmap_single(struct device *dev, struct i3c_dma *dma_xfer);
 
 int i3c_master_set_info(struct i3c_master_controller *master,
 			const struct i3c_device_info *info);
-- 
2.47.2


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