1 files changed, 434 insertions, 20 deletions

diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index e76d7d0..cb45136 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -96,6 +96,22 @@ static struct vendor_data vendor_st = {
 };
 
 /* Deals with DMA transactions */
+
+struct pl011_sgbuf {
+	struct scatterlist sg;
+	char *buf;
+};
+
+struct pl011_dmarx_data {
+	struct dma_chan		*chan;
+	struct completion	complete;
+	bool			use_buf_b;
+	struct pl011_sgbuf	sgbuf_a;
+	struct pl011_sgbuf	sgbuf_b;
+	dma_cookie_t		cookie;
+	bool			running;
+};
+
 struct pl011_dmatx_data {
 	struct dma_chan		*chan;
 	struct scatterlist	sg;
@@ -120,7 +136,9 @@ struct uart_amba_port {
 	char			type[12];
 #ifdef CONFIG_DMA_ENGINE
 	/* DMA stuff */
-	bool			using_dma;
+	bool			using_tx_dma;
+	bool			using_rx_dma;
+	struct pl011_dmarx_data dmarx;
 	struct pl011_dmatx_data	dmatx;
 #endif
 };
@@ -134,6 +152,31 @@ struct uart_amba_port {
 
 #define PL011_DMA_BUFFER_SIZE PAGE_SIZE
 
+static int pl011_sgbuf_init(struct dma_chan *chan, struct pl011_sgbuf *sg,
+	enum dma_data_direction dir)
+{
+	sg->buf = kmalloc(PL011_DMA_BUFFER_SIZE, GFP_KERNEL);
+	if (!sg->buf)
+		return -ENOMEM;
+
+	sg_init_one(&sg->sg, sg->buf, PL011_DMA_BUFFER_SIZE);
+
+	if (dma_map_sg(chan->device->dev, &sg->sg, 1, dir) != 1) {
+		kfree(sg->buf);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg,
+	enum dma_data_direction dir)
+{
+	if (sg->buf) {
+		dma_unmap_sg(chan->device->dev, &sg->sg, 1, dir);
+		kfree(sg->buf);
+	}
+}
+
 static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
 {
 	/* DMA is the sole user of the platform data right now */
@@ -153,7 +196,7 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
 		return;
 	}
 
-	/* Try to acquire a generic DMA engine slave channel */
+	/* Try to acquire a generic DMA engine slave TX channel */
 	dma_cap_zero(mask);
 	dma_cap_set(DMA_SLAVE, mask);
 
@@ -168,6 +211,28 @@ static void pl011_dma_probe_initcall(struct uart_amba_port *uap)
 
 	dev_info(uap->port.dev, "DMA channel TX %s\n",
 		 dma_chan_name(uap->dmatx.chan));
+
+	/* Optionally make use of an RX channel as well */
+	if (plat->dma_rx_param) {
+		struct dma_slave_config rx_conf = {
+			.src_addr = uap->port.mapbase + UART01x_DR,
+			.src_addr_width = DMA_SLAVE_BUSWIDTH_1_BYTE,
+			.direction = DMA_FROM_DEVICE,
+			.src_maxburst = uap->fifosize >> 1,
+		};
+
+		chan = dma_request_channel(mask, plat->dma_filter, plat->dma_rx_param);
+		if (!chan) {
+			dev_err(uap->port.dev, "no RX DMA channel!\n");
+			return;
+		}
+
+		dmaengine_slave_config(chan, &rx_conf);
+		uap->dmarx.chan = chan;
+
+		dev_info(uap->port.dev, "DMA channel RX %s\n",
+			 dma_chan_name(uap->dmarx.chan));
+	}
 }
 
 #ifndef MODULE
@@ -219,9 +284,10 @@ static void pl011_dma_remove(struct uart_amba_port *uap)
 	/* TODO: remove the initcall if it has not yet executed */
 	if (uap->dmatx.chan)
 		dma_release_channel(uap->dmatx.chan);
+	if (uap->dmarx.chan)
+		dma_release_channel(uap->dmarx.chan);
 }
 
-
 /* Forward declare this for the refill routine */
 static int pl011_dma_tx_refill(struct uart_amba_port *uap);
 
@@ -380,7 +446,7 @@ static int pl011_dma_tx_refill(struct uart_amba_port *uap)
  */
 static bool pl011_dma_tx_irq(struct uart_amba_port *uap)
 {
-	if (!uap->using_dma)
+	if (!uap->using_tx_dma)
 		return false;
 
 	/*
@@ -432,7 +498,7 @@ static inline bool pl011_dma_tx_start(struct uart_amba_port *uap)
 {
 	u16 dmacr;
 
-	if (!uap->using_dma)
+	if (!uap->using_tx_dma)
 		return false;
 
 	if (!uap->port.x_char) {
@@ -492,7 +558,7 @@ static void pl011_dma_flush_buffer(struct uart_port *port)
 {
 	struct uart_amba_port *uap = (struct uart_amba_port *)port;
 
-	if (!uap->using_dma)
+	if (!uap->using_tx_dma)
 		return;
 
 	/* Avoid deadlock with the DMA engine callback */
@@ -508,9 +574,260 @@ static void pl011_dma_flush_buffer(struct uart_port *port)
 	}
 }
 
+static void pl011_dma_rx_callback(void *data);
+
+static int pl011_dma_rx_trigger_dma(struct uart_amba_port *uap)
+{
+	struct dma_chan *rxchan = uap->dmarx.chan;
+	struct dma_device *dma_dev;
+	struct pl011_dmarx_data *dmarx = &uap->dmarx;
+	struct dma_async_tx_descriptor *desc;
+	struct pl011_sgbuf *sgbuf;
+
+	if (!rxchan)
+		return -EIO;
+
+	/* Start the RX DMA job */
+	sgbuf = uap->dmarx.use_buf_b ?
+		&uap->dmarx.sgbuf_b : &uap->dmarx.sgbuf_a;
+	dma_dev = rxchan->device;
+	desc = rxchan->device->device_prep_slave_sg(rxchan, &sgbuf->sg, 1,
+					DMA_FROM_DEVICE,
+					DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+	/*
+	 * If the DMA engine is busy and cannot prepare a
+	 * channel, no big deal, the driver will fall back
+	 * to interrupt mode as a result of this error code.
+	 */
+	if (!desc) {
+		uap->dmarx.running = false;
+		dmaengine_terminate_all(rxchan);
+		return -EBUSY;
+	}
+
+	/* Some data to go along to the callback */
+	desc->callback = pl011_dma_rx_callback;
+	desc->callback_param = uap;
+	dmarx->cookie = dmaengine_submit(desc);
+	dma_async_issue_pending(rxchan);
+
+	uap->dmacr |= UART011_RXDMAE;
+	writew(uap->dmacr, uap->port.membase + UART011_DMACR);
+	uap->dmarx.running = true;
+
+	uap->im &= ~UART011_RXIM;
+	writew(uap->im, uap->port.membase + UART011_IMSC);
+
+	return 0;
+}
+
+/*
+ * This is called when either the DMA job is complete, or
+ * the FIFO timeout interrupt occurred. This must be called
+ * with the port spinlock uap->port.lock held.
+ */
+static void pl011_dma_rx_chars(struct uart_amba_port *uap,
+			       u32 pending, bool use_buf_b,
+			       bool readfifo)
+{
+	struct tty_struct *tty = uap->port.state->port.tty;
+	struct pl011_sgbuf *sgbuf = use_buf_b ?
+		&uap->dmarx.sgbuf_b : &uap->dmarx.sgbuf_a;
+	struct device *dev = uap->dmarx.chan->device->dev;
+	unsigned int status, ch, flag;
+	int dma_count = 0;
+	u32 fifotaken = 0; /* only used for vdbg() */
+
+	/* Pick everything from the DMA first */
+	if (pending) {
+		/* Sync in buffer */
+		dma_sync_sg_for_cpu(dev, &sgbuf->sg, 1, DMA_FROM_DEVICE);
+
+		/*
+		 * First take all chars in the DMA pipe, then look in the FIFO.
+		 * Note that tty_insert_flip_buf() tries to take as many chars
+		 * as it can.
+		 */
+		dma_count = tty_insert_flip_string(uap->port.state->port.tty,
+						   sgbuf->buf, pending);
+
+		/* Return buffer to device */
+		dma_sync_sg_for_device(dev, &sgbuf->sg, 1, DMA_FROM_DEVICE);
+
+		uap->port.icount.rx += dma_count;
+		if (dma_count < pending)
+			dev_warn(uap->port.dev,
+				 "couldn't insert all characters (TTY is full?)\n");
+	}
+
+	/*
+	 * Only continue with trying to read the FIFO if all DMA chars have
+	 * been taken first.
+	 */
+	if (dma_count == pending && readfifo) {
+		/* Clear any error flags */
+		writew(UART011_OEIS | UART011_BEIS | UART011_PEIS | UART011_FEIS,
+		       uap->port.membase + UART011_ICR);
+
+		/*
+		 * If we read all the DMA'd characters, and we had an
+		 * incomplete buffer, that could be due to an rx error,
+		 * or maybe we just timed out. Read any pending chars
+		 * and check the error status.
+		 */
+		while (1) {
+			status = readw(uap->port.membase + UART01x_FR);
+			if (status & UART01x_FR_RXFE)
+				break;
+
+			/* Take chars from the FIFO and update status */
+			ch = readw(uap->port.membase + UART01x_DR) |
+			       UART_DUMMY_DR_RX;
+			flag = TTY_NORMAL;
+			uap->port.icount.rx++;
+			fifotaken++;
+
+			/*
+			 * Error conditions will only occur in the FIFO,
+			 * these will trigger an immediate interrupt and
+			 * stop the DMA job, so we will always find the
+			 * error in the FIFO, never in the DMA buffer.
+			 */
+			if (unlikely(ch & UART_DR_ERROR)) {
+				if (ch & UART011_DR_BE) {
+					ch &= ~(UART011_DR_FE | UART011_DR_PE);
+					uap->port.icount.brk++;
+					if (uart_handle_break(&uap->port))
+						continue;
+				} else if (ch & UART011_DR_PE)
+					uap->port.icount.parity++;
+				else if (ch & UART011_DR_FE)
+					uap->port.icount.frame++;
+				if (ch & UART011_DR_OE)
+					uap->port.icount.overrun++;
+
+				ch &= uap->port.read_status_mask;
+
+				if (ch & UART011_DR_BE)
+					flag = TTY_BREAK;
+				else if (ch & UART011_DR_PE)
+					flag = TTY_PARITY;
+				else if (ch & UART011_DR_FE)
+					flag = TTY_FRAME;
+			}
+
+			if (uart_handle_sysrq_char(&uap->port, ch & 255))
+				continue;
+
+			uart_insert_char(&uap->port, ch, UART011_DR_OE, ch, flag);
+		}
+	}
+
+	spin_unlock(&uap->port.lock);
+	dev_vdbg(uap->port.dev,
+		 "Took %d chars from DMA buffer and %d chars from the FIFO\n",
+		 dma_count, fifotaken);
+	tty_flip_buffer_push(tty);
+	spin_lock(&uap->port.lock);
+}
+
+static void pl011_dma_rx_irq(struct uart_amba_port *uap)
+{
+	struct pl011_dmarx_data *dmarx = &uap->dmarx;
+	struct dma_chan *rxchan = dmarx->chan;
+	struct pl011_sgbuf *sgbuf = dmarx->use_buf_b ?
+		&dmarx->sgbuf_b : &dmarx->sgbuf_a;
+	size_t pending;
+	struct dma_tx_state state;
+	enum dma_status dmastat;
+
+	/*
+	 * Pause the transfer so we can trust the current counter,
+	 * do this before we pause the PL011 block, else we may
+	 * overflow the FIFO.
+	 */
+	if (dmaengine_pause(rxchan))
+		dev_err(uap->port.dev, "unable to pause DMA transfer\n");
+	dmastat = rxchan->device->device_tx_status(rxchan,
+						   dmarx->cookie, &state);
+	if (dmastat != DMA_PAUSED)
+		dev_err(uap->port.dev, "unable to pause DMA transfer\n");
+
+	/* Disable RX DMA - incoming data will wait in the FIFO */
+	uap->dmacr &= ~UART011_RXDMAE;
+	writew(uap->dmacr, uap->port.membase + UART011_DMACR);
+	uap->dmarx.running = false;
+
+	pending = sgbuf->sg.length - state.residue;
+	BUG_ON(pending > PL011_DMA_BUFFER_SIZE);
+	/* Then we terminate the transfer - we now know our residue */
+	dmaengine_terminate_all(rxchan);
+
+	/*
+	 * This will take the chars we have so far and insert
+	 * into the framework.
+	 */
+	pl011_dma_rx_chars(uap, pending, dmarx->use_buf_b, true);
+
+	/* Switch buffer & re-trigger DMA job */
+	dmarx->use_buf_b = !dmarx->use_buf_b;
+	if (pl011_dma_rx_trigger_dma(uap)) {
+		dev_dbg(uap->port.dev, "could not retrigger RX DMA job "
+			"fall back to interrupt mode\n");
+		uap->im |= UART011_RXIM;
+		writew(uap->im, uap->port.membase + UART011_IMSC);
+	}
+}
+
+static void pl011_dma_rx_callback(void *data)
+{
+	struct uart_amba_port *uap = data;
+	struct pl011_dmarx_data *dmarx = &uap->dmarx;
+	bool lastbuf = dmarx->use_buf_b;
+	int ret;
+
+	/*
+	 * This completion interrupt occurs typically when the
+	 * RX buffer is totally stuffed but no timeout has yet
+	 * occurred. When that happens, we just want the RX
+	 * routine to flush out the secondary DMA buffer while
+	 * we immediately trigger the next DMA job.
+	 */
+	spin_lock_irq(&uap->port.lock);
+	uap->dmarx.running = false;
+	dmarx->use_buf_b = !lastbuf;
+	ret = pl011_dma_rx_trigger_dma(uap);
+
+	pl011_dma_rx_chars(uap, PL011_DMA_BUFFER_SIZE, lastbuf, false);
+	spin_unlock_irq(&uap->port.lock);
+	/*
+	 * Do this check after we picked the DMA chars so we don't
+	 * get some IRQ immediately from RX.
+	 */
+	if (ret) {
+		dev_dbg(uap->port.dev, "could not retrigger RX DMA job "
+			"fall back to interrupt mode\n");
+		uap->im |= UART011_RXIM;
+		writew(uap->im, uap->port.membase + UART011_IMSC);
+	}
+}
+
+/*
+ * Stop accepting received characters, when we're shutting down or
+ * suspending this port.
+ * Locking: called with port lock held and IRQs disabled.
+ */
+static inline void pl011_dma_rx_stop(struct uart_amba_port *uap)
+{
+	/* FIXME.  Just disable the DMA enable */
+	uap->dmacr &= ~UART011_RXDMAE;
+	writew(uap->dmacr, uap->port.membase + UART011_DMACR);
+}
 
 static void pl011_dma_startup(struct uart_amba_port *uap)
 {
+	int ret;
+
 	if (!uap->dmatx.chan)
 		return;
 
@@ -525,8 +842,33 @@ static void pl011_dma_startup(struct uart_amba_port *uap)
 
 	/* The DMA buffer is now the FIFO the TTY subsystem can use */
 	uap->port.fifosize = PL011_DMA_BUFFER_SIZE;
-	uap->using_dma = true;
+	uap->using_tx_dma = true;
+
+	if (!uap->dmarx.chan)
+		goto skip_rx;
+
+	/* Allocate and map DMA RX buffers */
+	ret = pl011_sgbuf_init(uap->dmarx.chan, &uap->dmarx.sgbuf_a,
+			       DMA_FROM_DEVICE);
+	if (ret) {
+		dev_err(uap->port.dev, "failed to init DMA %s: %d\n",
+			"RX buffer A", ret);
+		goto skip_rx;
+	}
+
+	ret = pl011_sgbuf_init(uap->dmarx.chan, &uap->dmarx.sgbuf_b,
+			       DMA_FROM_DEVICE);
+	if (ret) {
+		dev_err(uap->port.dev, "failed to init DMA %s: %d\n",
+			"RX buffer B", ret);
+		pl011_sgbuf_free(uap->dmarx.chan, &uap->dmarx.sgbuf_a,
+				 DMA_FROM_DEVICE);
+		goto skip_rx;
+	}
+
+	uap->using_rx_dma = true;
 
+skip_rx:
 	/* Turn on DMA error (RX/TX will be enabled on demand) */
 	uap->dmacr |= UART011_DMAONERR;
 	writew(uap->dmacr, uap->port.membase + UART011_DMACR);
@@ -539,11 +881,17 @@ static void pl011_dma_startup(struct uart_amba_port *uap)
 	if (uap->vendor->dma_threshold)
 		writew(ST_UART011_DMAWM_RX_16 | ST_UART011_DMAWM_TX_16,
 			       uap->port.membase + ST_UART011_DMAWM);
+
+	if (uap->using_rx_dma) {
+		if (pl011_dma_rx_trigger_dma(uap))
+			dev_dbg(uap->port.dev, "could not trigger initial "
+				"RX DMA job, fall back to interrupt mode\n");
+	}
 }
 
 static void pl011_dma_shutdown(struct uart_amba_port *uap)
 {
-	if (!uap->using_dma)
+	if (!(uap->using_tx_dma || uap->using_rx_dma))
 		return;
 
 	/* Disable RX and TX DMA */
@@ -555,19 +903,39 @@ static void pl011_dma_shutdown(struct uart_amba_port *uap)
 	writew(uap->dmacr, uap->port.membase + UART011_DMACR);
 	spin_unlock_irq(&uap->port.lock);
 
-	/* In theory, this should already be done by pl011_dma_flush_buffer */
-	dmaengine_terminate_all(uap->dmatx.chan);
-	if (uap->dmatx.queued) {
-		dma_unmap_sg(uap->dmatx.chan->device->dev, &uap->dmatx.sg, 1,
-			     DMA_TO_DEVICE);
-		uap->dmatx.queued = false;
+	if (uap->using_tx_dma) {
+		/* In theory, this should already be done by pl011_dma_flush_buffer */
+		dmaengine_terminate_all(uap->dmatx.chan);
+		if (uap->dmatx.queued) {
+			dma_unmap_sg(uap->dmatx.chan->device->dev, &uap->dmatx.sg, 1,
+				     DMA_TO_DEVICE);
+			uap->dmatx.queued = false;
+		}
+
+		kfree(uap->dmatx.buf);
+		uap->using_tx_dma = false;
+	}
+
+	if (uap->using_rx_dma) {
+		dmaengine_terminate_all(uap->dmarx.chan);
+		/* Clean up the RX DMA */
+		pl011_sgbuf_free(uap->dmarx.chan, &uap->dmarx.sgbuf_a, DMA_FROM_DEVICE);
+		pl011_sgbuf_free(uap->dmarx.chan, &uap->dmarx.sgbuf_b, DMA_FROM_DEVICE);
+		uap->using_rx_dma = false;
 	}
+}
 
-	kfree(uap->dmatx.buf);
+static inline bool pl011_dma_rx_available(struct uart_amba_port *uap)
+{
+	return uap->using_rx_dma;
+}
 
-	uap->using_dma = false;
+static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
+{
+	return uap->using_rx_dma && uap->dmarx.running;
 }
 
+
 #else
 /* Blank functions if the DMA engine is not available */
 static inline void pl011_dma_probe(struct uart_amba_port *uap)
@@ -600,6 +968,29 @@ static inline bool pl011_dma_tx_start(struct uart_amba_port *uap)
 	return false;
 }
 
+static inline void pl011_dma_rx_irq(struct uart_amba_port *uap)
+{
+}
+
+static inline void pl011_dma_rx_stop(struct uart_amba_port *uap)
+{
+}
+
+static inline int pl011_dma_rx_trigger_dma(struct uart_amba_port *uap)
+{
+	return -EIO;
+}
+
+static inline bool pl011_dma_rx_available(struct uart_amba_port *uap)
+{
+	return false;
+}
+
+static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
+{
+	return false;
+}
+
 #define pl011_dma_flush_buffer	NULL
 #endif
 
@@ -630,6 +1021,8 @@ static void pl011_stop_rx(struct uart_port *port)
 	uap->im &= ~(UART011_RXIM|UART011_RTIM|UART011_FEIM|
 		     UART011_PEIM|UART011_BEIM|UART011_OEIM);
 	writew(uap->im, uap->port.membase + UART011_IMSC);
+
+	pl011_dma_rx_stop(uap);
 }
 
 static void pl011_enable_ms(struct uart_port *port)
@@ -688,6 +1081,19 @@ static void pl011_rx_chars(struct uart_amba_port *uap)
 	}
 	spin_unlock(&uap->port.lock);
 	tty_flip_buffer_push(tty);
+	/*
+	 * If we were temporarily out of DMA mode for a while,
+	 * attempt to switch back to DMA mode again.
+	 */
+	if (pl011_dma_rx_available(uap)) {
+		if (pl011_dma_rx_trigger_dma(uap)) {
+			dev_dbg(uap->port.dev, "could not trigger RX DMA job "
+				"fall back to interrupt mode again\n");
+			uap->im |= UART011_RXIM;
+		} else
+			uap->im &= ~UART011_RXIM;
+		writew(uap->im, uap->port.membase + UART011_IMSC);
+	}
 	spin_lock(&uap->port.lock);
 }
 
@@ -767,8 +1173,12 @@ static irqreturn_t pl011_int(int irq, void *dev_id)
 					  UART011_RXIS),
 			       uap->port.membase + UART011_ICR);
 
-			if (status & (UART011_RTIS|UART011_RXIS))
-				pl011_rx_chars(uap);
+			if (status & (UART011_RTIS|UART011_RXIS)) {
+				if (pl011_dma_rx_running(uap))
+					pl011_dma_rx_irq(uap);
+				else
+					pl011_rx_chars(uap);
+			}
 			if (status & (UART011_DSRMIS|UART011_DCDMIS|
 				      UART011_CTSMIS|UART011_RIMIS))
 				pl011_modem_status(uap);
@@ -945,10 +1355,14 @@ static int pl011_startup(struct uart_port *port)
 	pl011_dma_startup(uap);
 
 	/*
-	 * Finally, enable interrupts
+	 * Finally, enable interrupts, only timeouts when using DMA
+	 * if initial RX DMA job failed, start in interrupt mode
+	 * as well.
 	 */
 	spin_lock_irq(&uap->port.lock);
-	uap->im = UART011_RXIM | UART011_RTIM;
+	uap->im = UART011_RTIM;
+	if (!pl011_dma_rx_running(uap))
+		uap->im |= UART011_RXIM;
 	writew(uap->im, uap->port.membase + UART011_IMSC);
 	spin_unlock_irq(&uap->port.lock);