[PATCH 2/3] serial: mxs-auart: add the DMA support for mx28
Shawn Guo
shawn.guo at linaro.org
Wed Oct 17 23:20:39 EDT 2012
On Tue, Oct 16, 2012 at 02:03:05PM +0800, Huang Shijie wrote:
> Only we meet the following conditions, we can enable the DMA support for
> auart:
>
> (1) We enable the DMA support in the dts file, such as
> arch/arm/boot/dts/imx28.dtsi.
>
> (2) We enable the hardware flow control.
>
> (3) We use the mx28, not the mx23. Due to hardware bug(see errata: 2836),
> we can not add the DMA support to mx23.
>
> Signed-off-by: Huang Shijie <b32955 at freescale.com>
> ---
> .../bindings/tty/serial/fsl-mxs-auart.txt | 7 +
> drivers/tty/serial/mxs-auart.c | 307 +++++++++++++++++++-
> 2 files changed, 311 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> index a154bf1..67e54b4 100644
> --- a/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> +++ b/Documentation/devicetree/bindings/tty/serial/fsl-mxs-auart.txt
> @@ -6,11 +6,18 @@ Required properties:
> - reg : Address and length of the register set for the device
> - interrupts : Should contain the auart interrupt numbers
>
> +Optional properties:
> +- fsl,auart-dma-channel : The DMA channels, the first is for RX, the other
> + is for TX.
> +- fsl,auart-enable-dma : Enable the DMA support for the auart.
> +
If we want to have it decided by device tree, can we drop the property
and simply check if "fsl,auart-dma-channel" presents?
> Example:
> auart0: serial at 8006a000 {
> compatible = "fsl,imx28-auart";
> reg = <0x8006a000 0x2000>;
> interrupts = <112 70 71>;
> + fsl,auart-dma-channel = <8 9>;
> + fsl,auart-enable-dma;
> };
>
> Note: Each auart port should have an alias correctly numbered in "aliases"
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index cd9ec1d..2271330 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -34,6 +34,8 @@
> #include <linux/io.h>
> #include <linux/pinctrl/consumer.h>
> #include <linux/of_device.h>
> +#include <linux/dma-mapping.h>
> +#include <linux/fsl/mxs-dma.h>
>
> #include <asm/cacheflush.h>
>
> @@ -76,7 +78,15 @@
>
> #define AUART_CTRL0_SFTRST (1 << 31)
> #define AUART_CTRL0_CLKGATE (1 << 30)
> +#define AUART_CTRL0_RXTO_ENABLE (1 << 27)
> +#define AUART_CTRL0_RXTIMEOUT(v) (((v) & 0x7ff) << 16)
> +#define AUART_CTRL0_XFER_COUNT(v) ((v) & 0xffff)
>
> +#define AUART_CTRL1_XFER_COUNT(v) ((v) & 0xffff)
> +
> +#define AUART_CTRL2_DMAONERR (1 << 26)
> +#define AUART_CTRL2_TXDMAE (1 << 25)
> +#define AUART_CTRL2_RXDMAE (1 << 24)
> #define AUART_CTRL2_CTSEN (1 << 15)
> #define AUART_CTRL2_RTSEN (1 << 14)
> #define AUART_CTRL2_RTS (1 << 11)
> @@ -116,12 +126,15 @@
> #define AUART_STAT_BERR (1 << 18)
> #define AUART_STAT_PERR (1 << 17)
> #define AUART_STAT_FERR (1 << 16)
> +#define AUART_STAT_RXCOUNT_MASK 0xffff
>
> static struct uart_driver auart_driver;
>
> struct mxs_auart_port {
> struct uart_port port;
>
> +#define MXS_AUART_DMA_CONFIG 0x1
> +#define MXS_AUART_DMA_ENABLED 0x2
> unsigned int flags;
> unsigned int ctrl;
>
> @@ -130,16 +143,116 @@ struct mxs_auart_port {
> struct clk *clk;
> struct device *dev;
> struct platform_device *pdev;
> +
> + /* for DMA */
> + struct mxs_dma_data dma_data;
> + int dma_channel_rx, dma_channel_tx;
> + int dma_irq_rx, dma_irq_tx;
> + int dma_channel;
> +
> + struct scatterlist tx_sgl;
> + struct dma_chan *tx_dma_chan;
> + void *tx_dma_buf;
> +
> + struct scatterlist rx_sgl;
> + struct dma_chan *rx_dma_chan;
> + void *rx_dma_buf;
> };
>
> +static inline bool auart_dma_enabled(struct mxs_auart_port *s)
> +{
> + return s->flags & MXS_AUART_DMA_ENABLED;
> +}
> +
> static void mxs_auart_stop_tx(struct uart_port *u);
>
> #define to_auart_port(u) container_of(u, struct mxs_auart_port, port)
>
> +static inline void mxs_auart_tx_chars(struct mxs_auart_port *s);
> +
> +static void dma_tx_callback(void *param)
> +{
> + struct mxs_auart_port *s = param;
> + struct circ_buf *xmit = &s->port.state->xmit;
> +
> + dma_unmap_sg(s->dev, &s->tx_sgl, 1, DMA_TO_DEVICE);
> +
> + /* wake up the possible processes. */
> + if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
> + uart_write_wakeup(&s->port);
> +
> + mxs_auart_tx_chars(s);
> +}
> +
> +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size)
> +{
> + struct dma_async_tx_descriptor *desc;
> + struct scatterlist *sgl = &s->tx_sgl;
> + struct dma_chan *channel = s->tx_dma_chan;
> + u32 pio[1];
One element array looks strange to me.
> +
> + /* [1] : send PIO. Note, the first pio word is CTRL1. */
> + pio[0] = AUART_CTRL1_XFER_COUNT(size);
> + desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
> + 1, DMA_TRANS_NONE, 0);
> + if (!desc) {
> + dev_err(s->dev, "step 1 error\n");
> + return -EINVAL;
> + }
> +
> + /* [2] : set DMA buffer. */
> + sg_init_one(sgl, s->tx_dma_buf, size);
> + dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE);
> + desc = dmaengine_prep_slave_sg(channel, sgl,
> + 1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> + if (!desc) {
> + dev_err(s->dev, "step 2 error\n");
> + return -EINVAL;
> + }
> +
> + /* [3] : submit the DMA */
> + desc->callback = dma_tx_callback;
> + desc->callback_param = s;
> + dmaengine_submit(desc);
> + dma_async_issue_pending(channel);
> + return 0;
> +}
> +
> static inline void mxs_auart_tx_chars(struct mxs_auart_port *s)
I'm not sure why this function is inline from the beginning. It
becomes even more inappropriate after you add more codes below.
Shawn
> {
> struct circ_buf *xmit = &s->port.state->xmit;
>
> + if (auart_dma_enabled(s)) {
> + int i = 0;
> + int size;
> + void *buffer = s->tx_dma_buf;
> + enum dma_status status;
> +
> + /* Check whether there is pending DMA operations. */
> + status = dmaengine_tx_status(s->tx_dma_chan, 0, NULL);
> + if (status != DMA_SUCCESS)
> + return;
> +
> + while (!uart_circ_empty(xmit) && !uart_tx_stopped(&s->port)) {
> + size = min_t(u32, UART_XMIT_SIZE - i,
> + CIRC_CNT_TO_END(xmit->head,
> + xmit->tail,
> + UART_XMIT_SIZE));
> + memcpy(buffer + i, xmit->buf + xmit->tail, size);
> + xmit->tail = (xmit->tail + size) & (UART_XMIT_SIZE - 1);
> +
> + i += size;
> + if (i >= UART_XMIT_SIZE)
> + break;
> + }
> +
> + if (uart_tx_stopped(&s->port))
> + mxs_auart_stop_tx(&s->port);
> + if (i)
> + mxs_auart_dma_tx(s, i);
> + return;
> + }
> +
> while (!(readl(s->port.membase + AUART_STAT) &
> AUART_STAT_TXFF)) {
> if (s->port.x_char) {
> @@ -293,10 +406,155 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
> return mctrl;
> }
>
> +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param)
> +{
> + struct mxs_auart_port *s = param;
> +
> + if (!mxs_dma_is_apbx(chan))
> + return false;
> +
> + if (s->dma_channel == chan->chan_id) {
> + chan->private = &s->dma_data;
> + return true;
> + }
> + return false;
> +}
> +
> +static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
> +static void dma_rx_callback(void *arg)
> +{
> + struct mxs_auart_port *s = (struct mxs_auart_port *) arg;
> + struct tty_struct *tty = s->port.state->port.tty;
> + int count;
> + u32 stat;
> +
> + stat = readl(s->port.membase + AUART_STAT);
> + stat &= ~(AUART_STAT_OERR | AUART_STAT_BERR |
> + AUART_STAT_PERR | AUART_STAT_FERR);
> +
> + count = stat & AUART_STAT_RXCOUNT_MASK;
> + tty_insert_flip_string(tty, s->rx_dma_buf, count);
> +
> + writel(stat, s->port.membase + AUART_STAT);
> + tty_flip_buffer_push(tty);
> +
> + /* start the next DMA for RX. */
> + mxs_auart_dma_prep_rx(s);
> +}
> +
> +static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s)
> +{
> + struct dma_async_tx_descriptor *desc;
> + struct scatterlist *sgl = &s->rx_sgl;
> + struct dma_chan *channel = s->rx_dma_chan;
> + u32 pio[1];
> +
> + /* [1] : send PIO */
> + pio[0] = AUART_CTRL0_RXTO_ENABLE
> + | AUART_CTRL0_RXTIMEOUT(0x80)
> + | AUART_CTRL0_XFER_COUNT(UART_XMIT_SIZE);
> + desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)pio,
> + 1, DMA_TRANS_NONE, 0);
> + if (!desc) {
> + dev_err(s->dev, "step 1 error\n");
> + return -EINVAL;
> + }
> +
> + /* [2] : send DMA request */
> + sg_init_one(sgl, s->rx_dma_buf, UART_XMIT_SIZE);
> + dma_map_sg(s->dev, sgl, 1, DMA_FROM_DEVICE);
> + desc = dmaengine_prep_slave_sg(channel, sgl, 1, DMA_DEV_TO_MEM,
> + DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
> + if (!desc) {
> + dev_err(s->dev, "step 2 error\n");
> + return -1;
> + }
> +
> + /* [3] : submit the DMA, but do not issue it. */
> + desc->callback = dma_rx_callback;
> + desc->callback_param = s;
> + dmaengine_submit(desc);
> + dma_async_issue_pending(channel);
> + return 0;
> +}
> +
> +static void mxs_auart_dma_exit_channel(struct mxs_auart_port *s)
> +{
> + if (s->tx_dma_chan) {
> + dma_release_channel(s->tx_dma_chan);
> + s->tx_dma_chan = NULL;
> + }
> + if (s->rx_dma_chan) {
> + dma_release_channel(s->rx_dma_chan);
> + s->rx_dma_chan = NULL;
> + }
> +
> + kfree(s->tx_dma_buf);
> + kfree(s->rx_dma_buf);
> + s->tx_dma_buf = NULL;
> + s->rx_dma_buf = NULL;
> +}
> +
> +static void mxs_auart_dma_exit(struct mxs_auart_port *s)
> +{
> +
> + writel(AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE | AUART_CTRL2_DMAONERR,
> + s->port.membase + AUART_CTRL2_CLR);
> +
> + mxs_auart_dma_exit_channel(s);
> + s->flags &= ~MXS_AUART_DMA_ENABLED;
> +}
> +
> +static int mxs_auart_dma_init(struct mxs_auart_port *s)
> +{
> + dma_cap_mask_t mask;
> +
> + if (auart_dma_enabled(s))
> + return 0;
> +
> + /* We do not get the right DMA channels. */
> + if (s->dma_channel_rx == -1 || s->dma_channel_rx == -1)
> + return -EINVAL;
> +
> + /* init for RX */
> + dma_cap_zero(mask);
> + dma_cap_set(DMA_SLAVE, mask);
> + s->dma_channel = s->dma_channel_rx;
> + s->dma_data.chan_irq = s->dma_irq_rx;
> + s->rx_dma_chan = dma_request_channel(mask, mxs_auart_dma_filter, s);
> + if (!s->rx_dma_chan)
> + goto err_out;
> + s->rx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
> + if (!s->rx_dma_buf)
> + goto err_out;
> +
> + /* init for TX */
> + s->dma_channel = s->dma_channel_tx;
> + s->dma_data.chan_irq = s->dma_irq_tx;
> + s->tx_dma_chan = dma_request_channel(mask, mxs_auart_dma_filter, s);
> + if (!s->tx_dma_chan)
> + goto err_out;
> + s->tx_dma_buf = kzalloc(UART_XMIT_SIZE, GFP_KERNEL | GFP_DMA);
> + if (!s->tx_dma_buf)
> + goto err_out;
> +
> + /* set the flags */
> + s->flags |= MXS_AUART_DMA_ENABLED;
> + dev_dbg(s->dev, "enabled the DMA support.");
> +
> + return 0;
> +
> +err_out:
> + mxs_auart_dma_exit_channel(s);
> + return -EINVAL;
> +
> +}
> +
> static void mxs_auart_settermios(struct uart_port *u,
> struct ktermios *termios,
> struct ktermios *old)
> {
> + struct mxs_auart_port *s = to_auart_port(u);
> u32 bm, ctrl, ctrl2, div;
> unsigned int cflag, baud;
>
> @@ -368,10 +626,23 @@ static void mxs_auart_settermios(struct uart_port *u,
> ctrl |= AUART_LINECTRL_STP2;
>
> /* figure out the hardware flow control settings */
> - if (cflag & CRTSCTS)
> + if (cflag & CRTSCTS) {
> + /*
> + * The DMA has a bug(see errata:2836) in mx23.
> + * So we can not implement the DMA for auart in mx23,
> + * we can only implement the DMA support for auart
> + * in mx28.
> + */
> + if (!AUART_IS_MX23(s) && (s->flags & MXS_AUART_DMA_CONFIG)) {
> + if (!mxs_auart_dma_init(s))
> + /* enable DMA tranfer */
> + ctrl2 |= AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE
> + | AUART_CTRL2_DMAONERR;
> + }
> ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
> - else
> + } else {
> ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
> + }
>
> /* set baud rate */
> baud = uart_get_baud_rate(u, termios, old, 0, u->uartclk);
> @@ -383,6 +654,17 @@ static void mxs_auart_settermios(struct uart_port *u,
> writel(ctrl2, u->membase + AUART_CTRL2);
>
> uart_update_timeout(u, termios->c_cflag, baud);
> +
> + /* prepare for the DMA RX. */
> + if (auart_dma_enabled(s)) {
> + if (!mxs_auart_dma_prep_rx(s)) {
> + /* Disable the normal RX interrupt. */
> + writel(AUART_INTR_RXIEN, u->membase + AUART_INTR_CLR);
> + } else {
> + mxs_auart_dma_exit(s);
> + dev_err(s->dev, "We can not start up the DMA.\n");
> + }
> + }
> }
>
> static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
> @@ -461,6 +743,9 @@ static void mxs_auart_shutdown(struct uart_port *u)
> {
> struct mxs_auart_port *s = to_auart_port(u);
>
> + if (auart_dma_enabled(s))
> + mxs_auart_dma_exit(s);
> +
> writel(AUART_CTRL2_UARTEN, u->membase + AUART_CTRL2_CLR);
>
> writel(AUART_INTR_RXIEN | AUART_INTR_RTIEN | AUART_INTR_CTSMIEN,
> @@ -707,6 +992,7 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
> struct platform_device *pdev)
> {
> struct device_node *np = pdev->dev.of_node;
> + u32 dma_channel[2];
> int ret;
>
> if (!np)
> @@ -722,6 +1008,22 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
>
> pdev->id_entry = of_match_device(mxs_auart_dt_ids, &pdev->dev)->data;
>
> + ret = of_property_read_u32_array(np, "fsl,auart-dma-channel",
> + dma_channel, 2);
> + if (ret == 0) {
> + s->dma_channel_rx = dma_channel[0];
> + s->dma_channel_tx = dma_channel[1];
> + } else {
> + s->dma_channel_rx = -1;
> + s->dma_channel_tx = -1;
> + }
> +
> + s->dma_irq_rx = platform_get_irq(pdev, 1);
> + s->dma_irq_tx = platform_get_irq(pdev, 2);
> +
> + if (of_property_read_bool(np, "fsl,auart-enable-dma"))
> + s->flags |= MXS_AUART_DMA_CONFIG;
> +
> return 0;
> }
>
> @@ -772,7 +1074,6 @@ static int __devinit mxs_auart_probe(struct platform_device *pdev)
> s->port.type = PORT_IMX;
> s->port.dev = s->dev = get_device(&pdev->dev);
>
> - s->flags = 0;
> s->ctrl = 0;
> s->pdev = pdev;
>
> --
> 1.7.0.4
>
>
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