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@xxxxxx>
---
drivers/spi/spi.c | 15 +++++++++++++++
include/linux/spi/spi.h | 2 ++
2 files changed, 17 insertions(+)
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index de2f2f90d799..2fb97f5b79ab 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -2722,6 +2722,7 @@ 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 ||
@@ -2747,8 +2748,22 @@ 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 != 0)
+ goto err;
+ }
ret = master->spi_flash_read(spi, msg);
+ if (master->dma_rx)
+ spi_unmap_buf(master, rx_dev, &msg->rx_sg,
+ DMA_FROM_DEVICE);
+
+err:
mutex_unlock(&master->bus_lock_mutex);
if (master->auto_runtime_pm)
pm_runtime_put(master->dev.parent);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 857a9a1d82b5..5b9c745eda92 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -1141,6 +1141,7 @@ 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
*/
struct spi_flash_read_message {
void *buf;
@@ -1153,6 +1154,7 @@ struct spi_flash_read_message {
u8 opcode_nbits;
u8 addr_nbits;
u8 data_nbits;
+ struct sg_table rx_sg;
};
/* SPI core interface for flash read support */
--
2.8.0
--
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