This patch adds support for DMA. Transfers are done with dma only if
they are longer than 16 bytes in order to achieve a better performance.
DMA setup introduces a little overhead and for transfers shorter than 16
bytes there is no performance improvement.
Signed-off-by: Radu Pirea <radu_nicolae.pi...@upb.ro>
---
drivers/spi/spi-at91-usart.c | 221 ++++++++++++++++++++++++++++++++++-
1 file changed, 219 insertions(+), 2 deletions(-)
diff --git a/drivers/spi/spi-at91-usart.c b/drivers/spi/spi-at91-usart.c
index a694d702e574..f3583bdd475b 100644
--- a/drivers/spi/spi-at91-usart.c
+++ b/drivers/spi/spi-at91-usart.c
@@ -8,9 +8,12 @@
#include <linux/clk.h>
#include <linux/delay.h>
+#include <linux/dmaengine.h>
+#include <linux/dma-direction.h>
#include <linux/interrupt.h>
#include <linux/kernel.h>
#include <linux/module.h>
+#include <linux/of_platform.h>
#include <linux/of_gpio.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>
@@ -59,6 +62,8 @@
#define US_INIT \
(US_MR_SPI_MASTER | US_MR_CHRL | US_MR_CLKO | US_MR_WRDBT)
+#define US_DMA_MIN_BYTES 16
+#define US_DMA_TIMEOUT (msecs_to_jiffies(1000))
/* Register access macros */
#define at91_usart_spi_readl(port, reg) \
@@ -72,14 +77,19 @@
writeb_relaxed((value), (port)->regs + US_##reg)
struct at91_usart_spi {
+ struct platform_device *mpdev;
struct spi_transfer *current_transfer;
void __iomem *regs;
struct device *dev;
struct clk *clk;
+ struct completion xfer_completion;
+
/*used in interrupt to protect data reading*/
spinlock_t lock;
+ phys_addr_t phybase;
+
int irq;
unsigned int current_tx_remaining_bytes;
unsigned int current_rx_remaining_bytes;
@@ -88,8 +98,182 @@ struct at91_usart_spi {
u32 status;
bool xfer_failed;
+ bool use_dma;
};
+static void dma_callback(void *data)
+{
+ struct spi_controller *ctlr = data;
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+
+ at91_usart_spi_writel(aus, IER, US_IR_RXRDY);
+ aus->current_rx_remaining_bytes = 0;
+ complete(&aus->xfer_completion);
+}
+
+static bool at91_usart_spi_can_dma(struct spi_controller *ctrl,
+ struct spi_device *spi,
+ struct spi_transfer *xfer)
+{
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctrl);
+
+ return aus->use_dma && xfer->len >= US_DMA_MIN_BYTES;
+}
+
+static int at91_usart_spi_configure_dma(struct spi_controller *ctlr,
+ struct at91_usart_spi *aus)
+{
+ struct dma_slave_config slave_config;
+ struct device *dev = &aus->mpdev->dev;
+ phys_addr_t phybase = aus->phybase;
+ dma_cap_mask_t mask;
+ int err = 0;
+
+ dma_cap_zero(mask);
+ dma_cap_set(DMA_SLAVE, mask);
+
+ ctlr->dma_tx = dma_request_slave_channel_reason(dev, "tx");
+ if (IS_ERR_OR_NULL(ctlr->dma_tx)) {
+ if (IS_ERR(ctlr->dma_tx)) {
+ err = PTR_ERR(ctlr->dma_tx);
+ goto at91_usart_spi_error_clear;
+ }
+
+ dev_dbg(dev,
+ "DMA TX channel not available, SPI unable to use
DMA\n");
+ err = -EBUSY;
+ goto at91_usart_spi_error_clear;
+ }
+
+ ctlr->dma_rx = dma_request_slave_channel_reason(dev, "rx");
+ if (IS_ERR_OR_NULL(ctlr->dma_rx)) {
+ if (IS_ERR(ctlr->dma_rx)) {
+ err = PTR_ERR(ctlr->dma_rx);
+ goto at91_usart_spi_error;
+ }
+
+ dev_dbg(dev,
+ "DMA RX channel not available, SPI unable to use
DMA\n");
+ err = -EBUSY;
+ goto at91_usart_spi_error;
+ }
+
+ slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.dst_addr = (dma_addr_t)phybase + US_THR;
+ slave_config.src_addr = (dma_addr_t)phybase + US_RHR;
+ slave_config.src_maxburst = 1;
+ slave_config.dst_maxburst = 1;
+ slave_config.device_fc = false;
+
+ slave_config.direction = DMA_DEV_TO_MEM;
+ if (dmaengine_slave_config(ctlr->dma_rx, &slave_config)) {
+ dev_err(&ctlr->dev,
+ "failed to configure rx dma channel\n");
+ err = -EINVAL;
+ goto at91_usart_spi_error;
+ }
+
+ slave_config.direction = DMA_MEM_TO_DEV;
+ if (dmaengine_slave_config(ctlr->dma_tx, &slave_config)) {
+ dev_err(&ctlr->dev,
+ "failed to configure tx dma channel\n");
+ err = -EINVAL;
+ goto at91_usart_spi_error;
+ }
+
+ aus->use_dma = true;
+ return 0;
+
+at91_usart_spi_error:
+ if (!IS_ERR_OR_NULL(ctlr->dma_tx))
+ dma_release_channel(ctlr->dma_tx);
+ if (!IS_ERR_OR_NULL(ctlr->dma_rx))
+ dma_release_channel(ctlr->dma_rx);
+ ctlr->dma_tx = NULL;
+ ctlr->dma_rx = NULL;
+
+at91_usart_spi_error_clear:
+ return err;
+}
+
+static void at91_usart_spi_release_dma(struct spi_controller *ctlr)
+{
+ if (ctlr->dma_rx)
+ dma_release_channel(ctlr->dma_rx);
+ if (ctlr->dma_tx)
+ dma_release_channel(ctlr->dma_tx);
+}
+
+static void at91_usart_spi_stop_dma(struct spi_controller *ctlr)
+{
+ if (ctlr->dma_rx)
+ dmaengine_terminate_all(ctlr->dma_rx);
+ if (ctlr->dma_tx)
+ dmaengine_terminate_all(ctlr->dma_tx);
+}
+
+static int at91_usart_spi_dma_transfer(struct spi_controller *ctlr,
+ struct spi_transfer *xfer)
+{
+ struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+ struct dma_chan *rxchan = ctlr->dma_rx;
+ struct dma_chan *txchan = ctlr->dma_tx;
+ struct dma_async_tx_descriptor *rxdesc;
+ struct dma_async_tx_descriptor *txdesc;
+ dma_cookie_t cookie;
+
+ /* Disable RX interrupt */
+ at91_usart_spi_writel(aus, IDR, US_IR_RXRDY);
+
+ rxdesc = dmaengine_prep_slave_sg(rxchan,
+ xfer->rx_sg.sgl,
+ xfer->rx_sg.nents,
+ DMA_DEV_TO_MEM,
+ DMA_PREP_INTERRUPT |
+ DMA_CTRL_ACK);
+ if (!rxdesc)
+ goto at91_usart_spi_err_dma;
+
+ txdesc = dmaengine_prep_slave_sg(txchan,
+ xfer->tx_sg.sgl,
+ xfer->tx_sg.nents,
+ DMA_MEM_TO_DEV,
+ DMA_PREP_INTERRUPT |
+ DMA_CTRL_ACK);
+ if (!txdesc)
+ goto at91_usart_spi_err_dma;
+
+ rxdesc->callback = dma_callback;
+ rxdesc->callback_param = ctlr;
+
+ cookie = rxdesc->tx_submit(rxdesc);
+ if (dma_submit_error(cookie))
+ goto at91_usart_spi_err_dma;
+
+ cookie = txdesc->tx_submit(txdesc);
+ if (dma_submit_error(cookie))
+ goto at91_usart_spi_err_dma;
+
+ rxchan->device->device_issue_pending(rxchan);
+ txchan->device->device_issue_pending(txchan);
+
+ return 0;
+
+at91_usart_spi_err_dma:
+ /* Enable RX interrupt if something fails and fallback to PIO */
+ at91_usart_spi_writel(aus, IER, US_IR_RXRDY);
+ at91_usart_spi_stop_dma(ctlr);
+
+ return -ENOMEM;
+}
+
+static unsigned long at91_usart_spi_dma_timeout(struct at91_usart_spi *aus)
+{
+ return wait_for_completion_timeout(&aus->xfer_completion,
+ US_DMA_TIMEOUT);
+}
+
static inline u32 at91_usart_spi_tx_ready(struct at91_usart_spi *aus)
{
return aus->status & US_IR_TXRDY;
@@ -222,6 +406,8 @@ static int at91_usart_spi_transfer_one(struct
spi_controller *ctlr,
struct spi_transfer *xfer)
{
struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+ unsigned long dma_timeout = 0;
+ int ret = 0;
at91_usart_spi_set_xfer_speed(aus, xfer);
aus->xfer_failed = false;
@@ -231,8 +417,25 @@ static int at91_usart_spi_transfer_one(struct
spi_controller *ctlr,
while ((aus->current_tx_remaining_bytes ||
aus->current_rx_remaining_bytes) && !aus->xfer_failed) {
- at91_usart_spi_read_status(aus);
- at91_usart_spi_tx(aus);
+ reinit_completion(&aus->xfer_completion);
+ if (at91_usart_spi_can_dma(ctlr, spi, xfer) &&
+ !ret) {
+ ret = at91_usart_spi_dma_transfer(ctlr, xfer);
+ if (ret)
+ continue;
+
+ dma_timeout = at91_usart_spi_dma_timeout(aus);
+
+ if (WARN_ON(dma_timeout == 0)) {
+ dev_err(&spi->dev, "DMA transfer timeout\n");
+ return -EIO;
+ }
+ aus->current_tx_remaining_bytes = 0;
+ } else {
+ at91_usart_spi_read_status(aus);
+ at91_usart_spi_tx(aus);
+ }
+
cpu_relax();
}
@@ -351,6 +554,7 @@ static int at91_usart_spi_probe(struct platform_device
*pdev)
controller->transfer_one = at91_usart_spi_transfer_one;
controller->prepare_message = at91_usart_spi_prepare_message;
controller->unprepare_message = at91_usart_spi_unprepare_message;
+ controller->can_dma = at91_usart_spi_can_dma;
controller->cleanup = at91_usart_spi_cleanup;
controller->max_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
US_MIN_CLK_DIV);
@@ -382,7 +586,17 @@ static int at91_usart_spi_probe(struct platform_device
*pdev)
aus->spi_clk = clk_get_rate(clk);
at91_usart_spi_init(aus);
+ aus->phybase = regs->start;
+
+ aus->mpdev = to_platform_device(pdev->dev.parent);
+
+ ret = at91_usart_spi_configure_dma(controller, aus);
+ if (ret)
+ goto at91_usart_fail_dma;
+
spin_lock_init(&aus->lock);
+ init_completion(&aus->xfer_completion);
+
ret = devm_spi_register_master(&pdev->dev, controller);
if (ret)
goto at91_usart_fail_register_master;
@@ -395,6 +609,8 @@ static int at91_usart_spi_probe(struct platform_device
*pdev)
return 0;
at91_usart_fail_register_master:
+ at91_usart_spi_release_dma(controller);
+at91_usart_fail_dma:
clk_disable_unprepare(clk);
at91_usart_spi_probe_fail:
spi_master_put(controller);
@@ -459,6 +675,7 @@ static int at91_usart_spi_remove(struct platform_device
*pdev)
struct spi_controller *ctlr = platform_get_drvdata(pdev);
struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
+ at91_usart_spi_release_dma(ctlr);
clk_disable_unprepare(aus->clk);
return 0;
--
2.21.0
