From: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
Add dma support for Atmel TWI which is available on sam9x5 and later.
When using dma for reception, you have to read only n-2 bytes. The last
two bytes are read manually. Don't doing this should cause to send the
STOP command too late and then to get extra data in the receive
register.
Signed-off-by: Ludovic Desroches <ludovic.desroches@xxxxxxxxx>
---
drivers/i2c/busses/i2c-at91.c | 306 ++++++++++++++++++++++++++++++++++++++++--
1 file changed, 298 insertions(+), 8 deletions(-)
diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c
index f82649b..74f7be9 100644
--- a/drivers/i2c/busses/i2c-at91.c
+++ b/drivers/i2c/busses/i2c-at91.c
@@ -19,6 +19,8 @@
#include <linux/clk.h>
#include <linux/completion.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
@@ -29,9 +31,11 @@
#include <linux/of_i2c.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
+#include <linux/platform_data/dma-atmel.h>
#define TWI_CLK_HZ 100000 /* max 400 Kbits/s */
#define AT91_I2C_TIMEOUT msecs_to_jiffies(100) /* transfer timeout */
+#define AT91_I2C_DMA_THRESHOLD 8 /* enable DMA if transfer size is bigger than this threshold */
/* AT91 TWI register definitions */
#define AT91_TWI_CR 0x0000 /* Control Register */
@@ -68,6 +72,18 @@ struct at91_twi_pdata {
unsigned clk_max_div;
unsigned clk_offset;
bool has_unre_flag;
+ bool has_dma_support;
+ struct at_dma_slave dma_slave;
+};
+
+struct at91_twi_dma {
+ struct dma_chan *chan_rx;
+ struct dma_chan *chan_tx;
+ struct scatterlist sg;
+ struct dma_async_tx_descriptor *data_desc;
+ enum dma_data_direction direction;
+ bool buf_mapped;
+ bool xfer_in_progress;
};
struct at91_twi_dev {
@@ -79,10 +95,13 @@ struct at91_twi_dev {
size_t buf_len;
struct i2c_msg *msg;
int irq;
+ unsigned imr;
unsigned transfer_status;
struct i2c_adapter adapter;
unsigned twi_cwgr_reg;
struct at91_twi_pdata *pdata;
+ bool use_dma;
+ struct at91_twi_dma dma;
};
static unsigned at91_twi_read(struct at91_twi_dev *dev, unsigned reg)
@@ -101,6 +120,17 @@ static void at91_disable_twi_interrupts(struct at91_twi_dev *dev)
AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY);
}
+static void at91_twi_irq_save(struct at91_twi_dev *dev)
+{
+ dev->imr = at91_twi_read(dev, AT91_TWI_IMR) & 0x7;
+ at91_disable_twi_interrupts(dev);
+}
+
+static void at91_twi_irq_restore(struct at91_twi_dev *dev)
+{
+ at91_twi_write(dev, AT91_TWI_IER, dev->imr);
+}
+
static void at91_init_twi_bus(struct at91_twi_dev *dev)
{
at91_disable_twi_interrupts(dev);
@@ -137,6 +167,28 @@ static void __devinit at91_calc_twi_clock(struct at91_twi_dev *dev, int twi_clk)
dev_dbg(dev->dev, "cdiv %d ckdiv %d\n", cdiv, ckdiv);
}
+static void at91_twi_dma_cleanup(struct at91_twi_dev *dev)
+{
+ struct at91_twi_dma *dma = &dev->dma;
+
+ at91_twi_irq_save(dev);
+
+ if (dma->xfer_in_progress) {
+ if (dma->direction == DMA_FROM_DEVICE)
+ dmaengine_terminate_all(dma->chan_rx);
+ else
+ dmaengine_terminate_all(dma->chan_tx);
+ dma->xfer_in_progress = false;
+ }
+ if (dma->buf_mapped) {
+ dma_unmap_single(dev->dev, sg_dma_address(&dma->sg),
+ dev->buf_len, dma->direction);
+ dma->buf_mapped = false;
+ }
+
+ at91_twi_irq_restore(dev);
+}
+
static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
{
if (dev->buf_len <= 0)
@@ -153,6 +205,60 @@ static void at91_twi_write_next_byte(struct at91_twi_dev *dev)
++dev->buf;
}
+static void at91_twi_write_data_dma_callback(void *data)
+{
+ struct at91_twi_dev *dev = (struct at91_twi_dev *)data;
+
+ dma_unmap_single(dev->dev, sg_dma_address(&dev->dma.sg),
+ dev->buf_len, DMA_MEM_TO_DEV);
+
+ at91_twi_write(dev, AT91_TWI_CR, AT91_TWI_STOP);
+}
+
+static void at91_twi_write_data_dma(struct at91_twi_dev *dev)
+{
+ dma_addr_t dma_addr;
+ struct dma_async_tx_descriptor *txdesc;
+ struct at91_twi_dma *dma = &dev->dma;
+ struct dma_chan *chan_tx = dma->chan_tx;
+
+ if (dev->buf_len <= 0)
+ return;
+
+ dma->direction = DMA_TO_DEVICE;
+
+ at91_twi_irq_save(dev);
+ dma_addr = dma_map_single(dev->dev, dev->buf, dev->buf_len,
+ DMA_TO_DEVICE);
+ if (dma_mapping_error(dev->dev, dma_addr)) {
+ dev_err(dev->dev, "dma map failed\n");
+ return;
+ }
+ dma->buf_mapped = true;
+ at91_twi_irq_restore(dev);
+ sg_dma_len(&dma->sg) = dev->buf_len;
+ sg_dma_address(&dma->sg) = dma_addr;
+
+ txdesc = dmaengine_prep_slave_sg(chan_tx, &dma->sg, 1, DMA_MEM_TO_DEV,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!txdesc) {
+ dev_err(dev->dev, "dma prep slave sg failed\n");
+ goto error;
+ }
+
+ txdesc->callback = at91_twi_write_data_dma_callback;
+ txdesc->callback_param = dev;
+
+ dma->xfer_in_progress = true;
+ dmaengine_submit(txdesc);
+ dma_async_issue_pending(chan_tx);
+
+ return;
+
+error:
+ at91_twi_dma_cleanup(dev);
+}
+
static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
{
if (dev->buf_len <= 0)
@@ -178,6 +284,61 @@ static void at91_twi_read_next_byte(struct at91_twi_dev *dev)
++dev->buf;
}
+static void at91_twi_read_data_dma_callback(void *data)
+{
+ struct at91_twi_dev *dev = (struct at91_twi_dev *)data;
+
+ dma_unmap_single(dev->dev, sg_dma_address(&dev->dma.sg),
+ dev->buf_len, DMA_DEV_TO_MEM);
+
+ /* The last two bytes have to be read without using dma */
+ dev->buf += dev->buf_len - 2;
+ dev->buf_len = 2;
+ at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_RXRDY);
+}
+
+static void at91_twi_read_data_dma(struct at91_twi_dev *dev)
+{
+ dma_addr_t dma_addr;
+ struct dma_async_tx_descriptor *rxdesc;
+ struct at91_twi_dma *dma = &dev->dma;
+ struct dma_chan *chan_rx = dma->chan_rx;
+
+ dma->direction = DMA_FROM_DEVICE;
+
+ /* Keep in mind that we won't use dma to read the last two bytes */
+ at91_twi_irq_save(dev);
+ dma_addr = dma_map_single(dev->dev, dev->buf, dev->buf_len - 2,
+ DMA_FROM_DEVICE);
+ if (dma_mapping_error(dev->dev, dma_addr)) {
+ dev_err(dev->dev, "dma map failed\n");
+ return;
+ }
+ dma->buf_mapped = true;
+ at91_twi_irq_restore(dev);
+ dma->sg.dma_address = dma_addr;
+ sg_dma_len(&dma->sg) = dev->buf_len - 2;
+
+ rxdesc = dmaengine_prep_slave_sg(chan_rx, &dma->sg, 1, DMA_DEV_TO_MEM,
+ DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ if (!rxdesc) {
+ dev_err(dev->dev, "dma prep slave sg failed\n");
+ goto error;
+ }
+
+ rxdesc->callback = at91_twi_read_data_dma_callback;
+ rxdesc->callback_param = dev;
+
+ dma->xfer_in_progress = true;
+ dmaengine_submit(rxdesc);
+ dma_async_issue_pending(dma->chan_rx);
+
+ return;
+
+error:
+ at91_twi_dma_cleanup(dev);
+}
+
static irqreturn_t atmel_twi_interrupt(int irq, void *dev_id)
{
struct at91_twi_dev *dev = dev_id;
@@ -224,12 +385,36 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
if (dev->buf_len <= 1 && !(dev->msg->flags & I2C_M_RECV_LEN))
start_flags |= AT91_TWI_STOP;
at91_twi_write(dev, AT91_TWI_CR, start_flags);
- at91_twi_write(dev, AT91_TWI_IER,
+ /*
+ * When using dma, the last byte has to be read manually in
+ * order to not send the stop command too late and then
+ * to receive extra data. In practice, there are some issues
+ * if you use the dma to read n-1 bytes because of latency.
+ * Reading n-2 bytes with dma and the two last ones manually
+ * seems to be the best solution.
+ */
+ if (dev->use_dma && (dev->buf_len > AT91_I2C_DMA_THRESHOLD)) {
+ at91_twi_read_data_dma(dev);
+ /*
+ * It is important to enable TXCOMP irq here because
+ * doing it only when transferring the last two bytes
+ * will mask NACK errors since TXCOMP is set when a
+ * NACK occurs.
+ */
+ at91_twi_write(dev, AT91_TWI_IER,
+ AT91_TWI_TXCOMP);
+ } else
+ at91_twi_write(dev, AT91_TWI_IER,
AT91_TWI_TXCOMP | AT91_TWI_RXRDY);
} else {
- at91_twi_write_next_byte(dev);
- at91_twi_write(dev, AT91_TWI_IER,
- AT91_TWI_TXCOMP | AT91_TWI_TXRDY);
+ if (dev->use_dma && (dev->buf_len > AT91_I2C_DMA_THRESHOLD)) {
+ at91_twi_write_data_dma(dev);
+ at91_twi_write(dev, AT91_TWI_IER, AT91_TWI_TXCOMP);
+ } else {
+ at91_twi_write_next_byte(dev);
+ at91_twi_write(dev, AT91_TWI_IER,
+ AT91_TWI_TXCOMP | AT91_TWI_TXRDY);
+ }
}
ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
@@ -237,23 +422,31 @@ static int at91_do_twi_transfer(struct at91_twi_dev *dev)
if (ret == 0) {
dev_err(dev->dev, "controller timed out\n");
at91_init_twi_bus(dev);
- return -ETIMEDOUT;
+ ret = -ETIMEDOUT;
+ goto error;
}
if (dev->transfer_status & AT91_TWI_NACK) {
dev_dbg(dev->dev, "received nack\n");
- return -EREMOTEIO;
+ ret = -EREMOTEIO;
+ goto error;
}
if (dev->transfer_status & AT91_TWI_OVRE) {
dev_err(dev->dev, "overrun while reading\n");
- return -EIO;
+ ret = -EIO;
+ goto error;
}
if (has_unre_flag && dev->transfer_status & AT91_TWI_UNRE) {
dev_err(dev->dev, "underrun while writing\n");
- return -EIO;
+ ret = -EIO;
+ goto error;
}
dev_dbg(dev->dev, "transfer complete\n");
return 0;
+
+error:
+ at91_twi_dma_cleanup(dev);
+ return ret;
}
static int at91_twi_xfer(struct i2c_adapter *adap, struct i2c_msg *msg, int num)
@@ -324,36 +517,42 @@ static struct at91_twi_pdata at91rm9200_config = {
.clk_max_div = 5,
.clk_offset = 3,
.has_unre_flag = true,
+ .has_dma_support = false,
};
static struct at91_twi_pdata at91sam9261_config = {
.clk_max_div = 5,
.clk_offset = 4,
.has_unre_flag = false,
+ .has_dma_support = false,
};
static struct at91_twi_pdata at91sam9260_config = {
.clk_max_div = 7,
.clk_offset = 4,
.has_unre_flag = false,
+ .has_dma_support = false,
};
static struct at91_twi_pdata at91sam9g20_config = {
.clk_max_div = 7,
.clk_offset = 4,
.has_unre_flag = false,
+ .has_dma_support = false,
};
static struct at91_twi_pdata at91sam9g10_config = {
.clk_max_div = 7,
.clk_offset = 4,
.has_unre_flag = false,
+ .has_dma_support = false,
};
static struct at91_twi_pdata at91sam9x5_config = {
.clk_max_div = 7,
.clk_offset = 4,
.has_unre_flag = false,
+ .has_dma_support = true,
};
static const struct platform_device_id at91_twi_devtypes[] = {
@@ -400,6 +599,90 @@ MODULE_DEVICE_TABLE(of, atmel_twi_dt_ids);
#define atmel_twi_dt_ids NULL
#endif
+static bool __devinit filter(struct dma_chan *chan, void *slave)
+{
+ struct at_dma_slave *sl = slave;
+
+ if (sl->dma_dev == chan->device->dev) {
+ chan->private = sl;
+ return true;
+ } else {
+ return false;
+ }
+}
+
+static int __devinit at91_twi_configure_dma(struct at91_twi_dev *dev, u32 phy_addr)
+{
+ int ret = 0;
+ struct at_dma_slave *sdata;
+ struct dma_slave_config slave_config;
+ struct at91_twi_dma *dma = &dev->dma;
+
+ sdata = &dev->pdata->dma_slave;
+
+ memset(&slave_config, 0, sizeof(slave_config));
+ slave_config.src_addr = (dma_addr_t)phy_addr + AT91_TWI_RHR;
+ slave_config.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.src_maxburst = 1;
+ slave_config.dst_addr = (dma_addr_t)phy_addr + AT91_TWI_THR;
+ slave_config.dst_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE;
+ slave_config.dst_maxburst = 1;
+ slave_config.device_fc = false;
+
+ if (sdata && sdata->dma_dev) {
+ dma_cap_mask_t mask;
+
+ dma_cap_zero(mask);
+ dma_cap_set(DMA_SLAVE, mask);
+ dma->chan_tx = dma_request_channel(mask, filter, sdata);
+ if (!dma->chan_tx) {
+ dev_err(dev->dev, "no DMA channel available for tx\n");
+ ret = -EBUSY;
+ goto error;
+ }
+ dma->chan_rx = dma_request_channel(mask, filter, sdata);
+ if (!dma->chan_rx) {
+ dev_err(dev->dev, "no DMA channel available for rx\n");
+ ret = -EBUSY;
+ goto error;
+ }
+ } else {
+ ret = -EINVAL;
+ goto error;
+ }
+
+ slave_config.direction = DMA_MEM_TO_DEV;
+ if (dmaengine_slave_config(dma->chan_tx, &slave_config)) {
+ dev_err(dev->dev, "failed to configure tx channel\n");
+ ret = -EINVAL;
+ goto error;
+ }
+
+ slave_config.direction = DMA_DEV_TO_MEM;
+ if (dmaengine_slave_config(dma->chan_rx, &slave_config)) {
+ dev_err(dev->dev, "failed to configure rx channel\n");
+ ret = -EINVAL;
+ goto error;
+ }
+
+ sg_init_table(&dma->sg, 1);
+ dma->buf_mapped = false;
+ dma->xfer_in_progress = false;
+
+ dev_info(dev->dev, "using %s (tx) and %s (rx) for DMA transfers\n",
+ dma_chan_name(dma->chan_tx), dma_chan_name(dma->chan_rx));
+
+ return ret;
+
+error:
+ dev_info(dev->dev, "can't use DMA\n");
+ if (dma->chan_rx)
+ dma_release_channel(dma->chan_rx);
+ if (dma->chan_tx)
+ dma_release_channel(dma->chan_tx);
+ return ret;
+}
+
static struct at91_twi_pdata * __devinit at91_twi_get_driver_data(
struct platform_device *pdev)
{
@@ -418,6 +701,7 @@ static int __devinit at91_twi_probe(struct platform_device *pdev)
struct at91_twi_dev *dev;
struct resource *mem;
int rc;
+ u32 phy_addr;
dev = devm_kzalloc(&pdev->dev, sizeof(*dev), GFP_KERNEL);
if (!dev)
@@ -428,6 +712,7 @@ static int __devinit at91_twi_probe(struct platform_device *pdev)
mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
if (!mem)
return -ENODEV;
+ phy_addr = mem->start;
dev->pdata = at91_twi_get_driver_data(pdev);
if (!dev->pdata)
@@ -457,6 +742,11 @@ static int __devinit at91_twi_probe(struct platform_device *pdev)
}
clk_prepare_enable(dev->clk);
+ if (dev->pdata->has_dma_support) {
+ if (at91_twi_configure_dma(dev, phy_addr) == 0)
+ dev->use_dma = true;
+ }
+
at91_calc_twi_clock(dev, TWI_CLK_HZ);
at91_init_twi_bus(dev);
--
1.7.11.3
--
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