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Commit f4502dd1 authored by Vignesh R's avatar Vignesh R Committed by Mark Brown
Browse files

spi: Add DMA support for spi_flash_read() 



Few SPI devices provide accelerated read interfaces to read from
SPI-NOR flash devices. These hardwares also support DMA to transfer data
from flash to memory either via mem-to-mem DMA or dedicated slave DMA
channels. Hence, add support for DMA in order to improve throughput and
reduce CPU load.
Use spi_map_buf() to get sg table for the buffer and pass it to SPI
driver.

Signed-off-by: default avatarVignesh R <vigneshr@ti.com>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent 1a695a90

drivers/spi/spi.c

+28 −0
Original line number Diff line number Diff line
@@ -849,6 +849,20 @@ static int __spi_unmap_msg(struct spi_master *master, struct spi_message *msg) 
	return 0;

}

#else /* !CONFIG_HAS_DMA */

static inline int spi_map_buf(struct spi_master *master,

			      struct device *dev, struct sg_table *sgt,

			      void *buf, size_t len,

			      enum dma_data_direction dir)

{

	return -EINVAL;

}



static inline void spi_unmap_buf(struct spi_master *master,

				 struct device *dev, struct sg_table *sgt,

				 enum dma_data_direction dir)

{

}



static inline int __spi_map_msg(struct spi_master *master,

				struct spi_message *msg)

{
@@ -2725,6 +2739,7 @@ int spi_flash_read(struct spi_device *spi, 


{

	struct spi_master *master = spi->master;

	struct device *rx_dev = NULL;

	int ret;



	if ((msg->opcode_nbits == SPI_NBITS_DUAL ||
@@ -2750,9 +2765,22 @@ int spi_flash_read(struct spi_device *spi, 
			return ret;

		}

	}



	mutex_lock(&master->bus_lock_mutex);

	if (master->dma_rx) {

		rx_dev = master->dma_rx->device->dev;

		ret = spi_map_buf(master, rx_dev, &msg->rx_sg,

				  msg->buf, msg->len,

				  DMA_FROM_DEVICE);

		if (!ret)

			msg->cur_msg_mapped = true;

	}

	ret = master->spi_flash_read(spi, msg);

	if (msg->cur_msg_mapped)

		spi_unmap_buf(master, rx_dev, &msg->rx_sg,

			      DMA_FROM_DEVICE);

	mutex_unlock(&master->bus_lock_mutex);



	if (master->auto_runtime_pm)

		pm_runtime_put(master->dev.parent);

include/linux/spi/spi.h

+4 −0
Original line number Diff line number Diff line
@@ -1143,6 +1143,8 @@ static inline ssize_t spi_w8r16be(struct spi_device *spi, u8 cmd) 
 * @opcode_nbits: number of lines to send opcode

 * @addr_nbits: number of lines to send address

 * @data_nbits: number of lines for data

 * @rx_sg: Scatterlist for receive data read from flash

 * @cur_msg_mapped: message has been mapped for DMA

 */

struct spi_flash_read_message {

	void *buf;
@@ -1155,6 +1157,8 @@ struct spi_flash_read_message { 
	u8 opcode_nbits;

	u8 addr_nbits;

	u8 data_nbits;

	struct sg_table rx_sg;

	bool cur_msg_mapped;

};



/* SPI core interface for flash read support */