Commit c3fdefc2 authored by Radu Pirea's avatar Radu Pirea Committed by Mark Brown

spi: at91-usart: add DMA support

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: default avatarRadu Pirea <radu_nicolae.pirea@upb.ro>
Signed-off-by: default avatarMark Brown <broonie@kernel.org>
parent f7b99e59
......@@ -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;
......@@ -216,6 +400,8 @@ 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;
......@@ -225,8 +411,25 @@ 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();
}
......@@ -345,6 +548,7 @@ 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);
......@@ -376,7 +580,17 @@ 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;
......@@ -389,6 +603,8 @@ 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);
......@@ -453,6 +669,7 @@ 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;
......
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment