Commit f8d9e56a authored by Jarkko Nikula's avatar Jarkko Nikula Committed by Alexandre Belloni
Browse files

i3c: master: Add helpers for DMA mapping and bounce buffer handling 



Some I3C controllers such as MIPI I3C HCI may pad the last DWORD (32-bit)
with stale data from the RX FIFO in DMA transfers if the receive length
is not DWORD aligned and when the device DMA is IOMMU mapped.

In such a case, a properly sized bounce buffer is required in order to
avoid possible data corruption. In a review discussion, proposal was to
have a common helpers in I3C core for DMA mapping and bounce buffer
handling.

Drivers may use the helper i3c_master_dma_map_single() to map a buffer
for a DMA transfer. It internally allocates a bounce buffer if buffer is
not DMA'able or when the driver requires it for a transfer.

Helper i3c_master_dma_unmap_single() does the needed cleanups and
data copying from the bounce buffer.

Signed-off-by: default avatarJarkko Nikula <jarkko.nikula@linux.intel.com>
Reviewed-by: default avatarFrank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20250822105630.2820009-2-jarkko.nikula@linux.intel.com


Signed-off-by: default avatarAlexandre Belloni <alexandre.belloni@bootlin.com>
parent d515503f

drivers/i3c/master.c

+74 −0
Original line number Diff line number Diff line
@@ -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

 * @force_bounce: true, force to use a bounce buffer,

 *                false, function will auto check is a bounce buffer required

 * @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 force_bounce, enum dma_data_direction dir)

{

	struct i3c_dma *dma_xfer __free(kfree) = NULL;

	void *bounce __free(kfree) = NULL;

	void *dma_buf = buf;



	dma_xfer = kzalloc(sizeof(*dma_xfer), GFP_KERNEL);

	if (!dma_xfer)

		return NULL;



	dma_xfer->dev = dev;

	dma_xfer->buf = buf;

	dma_xfer->dir = dir;

	dma_xfer->len = len;

	dma_xfer->map_len = len;



	if (is_vmalloc_addr(buf))

		force_bounce = true;



	if (force_bounce) {

		dma_xfer->map_len = ALIGN(len, cache_line_size());

		if (dir == DMA_FROM_DEVICE)

			bounce = kzalloc(dma_xfer->map_len, GFP_KERNEL);

		else

			bounce = kmemdup(buf, dma_xfer->map_len, GFP_KERNEL);

		if (!bounce)

			return NULL;

		dma_buf = bounce;

	}



	dma_xfer->addr = dma_map_single(dev, dma_buf, dma_xfer->map_len, dir);

	if (dma_mapping_error(dev, dma_xfer->addr))

		return NULL;



	dma_xfer->bounce_buf = no_free_ptr(bounce);

	return no_free_ptr(dma_xfer);

}

EXPORT_SYMBOL_GPL(i3c_master_dma_map_single);



/**

 * i3c_master_dma_unmap_single() - Unmap buffer after DMA

 * @dma_xfer: DMA transfer and mapping descriptor

 *

 * Unmap buffer and cleanup DMA transfer descriptor.

 */

void i3c_master_dma_unmap_single(struct i3c_dma *dma_xfer)

{

	dma_unmap_single(dma_xfer->dev, dma_xfer->addr,

			 dma_xfer->map_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

include/linux/i3c/master.h

+26 −0
Original line number Diff line number Diff line
@@ -558,6 +558,26 @@ 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

 * @dev: device object of a device doing DMA

 * @buf: destination/source buffer for DMA

 * @len: length of transfer

 * @map_len: length of DMA mapping

 * @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 {

	struct device *dev;

	void *buf;

	size_t len;

	size_t map_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 +595,12 @@ 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 force_bounce,

					  enum dma_data_direction dir);

void i3c_master_dma_unmap_single(struct i3c_dma *dma_xfer);

DEFINE_FREE(i3c_master_dma_unmap_single, void *,

	    if (_T) i3c_master_dma_unmap_single(_T))



int i3c_master_set_info(struct i3c_master_controller *master,

			const struct i3c_device_info *info);