i2c: at91: add dma support

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@atmel.com>
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
This commit is contained in:
Ludovic Desroches 2012-11-23 10:09:04 +01:00 committed by Wolfram Sang
parent 5f433819b3
commit 60937b2cdb

View file

@ -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 */
@ -69,6 +73,18 @@ 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 {
@ -80,10 +96,13 @@ 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)
@ -102,6 +121,17 @@ 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);
@ -138,6 +168,28 @@ 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)
@ -154,6 +206,60 @@ 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)
@ -179,6 +285,61 @@ 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;
@ -229,12 +390,36 @@ 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,
@ -242,23 +427,31 @@ 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)
@ -329,36 +522,42 @@ 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[] = {
@ -405,6 +604,90 @@ 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)
{
@ -423,6 +706,7 @@ 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)
@ -433,6 +717,7 @@ 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)
@ -462,6 +747,11 @@ 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);