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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: Vignesh R <vigneshr@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Vignesh R 2016-06-08 12:18:31 +05:30 committed by Mark Brown
parent 1a695a905c
commit f4502dd1da
2 changed files with 32 additions and 0 deletions
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28
drivers/spi/spi.c
View File

@ -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);

4
include/linux/spi/spi.h
View File

@ -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 */