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>

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 77e6e45951f4c5e1c69a81b6d4ddf370d7f1a075..c9a8d544e4678ab771c91b2699bf8486b6ac7edd 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -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);
 

diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index 1f03483f61e5714b1c07708fee2fe3d7ffa946e3..7b53af4ba5f8c8272fa1ba2bb9c68dbd28fe5a17 100644 (file)
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -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 */