From: Ludovic Desroches <[email protected]> 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 <[email protected]> --- drivers/i2c/busses/i2c-at91.c | 326 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 314 insertions(+), 12 deletions(-) diff --git a/drivers/i2c/busses/i2c-at91.c b/drivers/i2c/busses/i2c-at91.c index aa59a25..33219f8 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> @@ -30,6 +32,8 @@ #include <linux/platform_device.h> #include <linux/slab.h> +#include <mach/at_hdmac.h> + #define TWI_CLK_HZ 100000 /* max 400 Kbits/s */ #define AT91_I2C_TIMEOUT msecs_to_jiffies(100) /* transfer timeout */ @@ -65,9 +69,21 @@ #define AT91_TWI_THR 0x0034 /* Transmit Holding Register */ struct at91_twi_pdata { - unsigned clk_max_div; - unsigned clk_offset; - bool has_unre_flag; + 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) @@ -98,7 +117,18 @@ static void at91_twi_write(struct at91_twi_dev *dev, unsigned reg, unsigned val) static void at91_disable_twi_interrupts(struct at91_twi_dev *dev) { at91_twi_write(dev, AT91_TWI_IDR, - AT91_TWI_TXCOMP | AT91_TWI_RXRDY | AT91_TWI_TXRDY); + 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) @@ -137,6 +167,30 @@ 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) + dma->chan_rx->device->device_control(dma->chan_rx, + DMA_TERMINATE_ALL, 0); + else + dma->chan_tx->device->device_control(dma->chan_tx, + DMA_TERMINATE_ALL, 0); + 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 +207,65 @@ 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_TO_DEVICE); + + 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; + dma_cookie_t cookie; + 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 = chan_tx->device->device_prep_slave_sg(chan_tx, &dma->sg, + 1, DMA_TO_DEVICE, DMA_PREP_INTERRUPT | DMA_CTRL_ACK, NULL); + 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; + cookie = txdesc->tx_submit(txdesc); + if (dma_submit_error(cookie)) { + dev_err(dev->dev, "dma submit error\n"); + goto error; + } + dma->chan_tx->device->device_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 +291,66 @@ 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_FROM_DEVICE); + + /* 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; + dma_cookie_t cookie; + 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 = chan_rx->device->device_prep_slave_sg(chan_rx, &dma->sg, + 1, DMA_FROM_DEVICE, DMA_PREP_INTERRUPT | DMA_CTRL_ACK, NULL); + 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; + cookie = rxdesc->tx_submit(rxdesc); + if (dma_submit_error(cookie)) { + dev_err(dev->dev, "dma submit error\n"); + goto error; + } + dma->chan_rx->device->device_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 +397,36 @@ 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 > 2)) { + 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) { + 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 +434,31 @@ 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 +529,42 @@ 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 +611,90 @@ 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_TO_DEVICE; + 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_FROM_DEVICE; + 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 +713,7 @@ 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 +724,7 @@ 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 +754,11 @@ 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 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
