serial: 8250: Extract IIR logic steering from rx dma

Using fake IIR values to perform rx dma operations unnecessarily
conflates separate operations, stopping in-progress dma with starting
new dma.

Introduce serial8250_rx_dma_flush() to handle stopping in-progress dma
[omap8250 already has equivalent omap_8250_rx_dma_flush()].
Replace rx_dma(UART_IIR_RX_TIMEOUT) with the equivalent *_rx_dma_flush(),
and rx_dma(0) with the equivalent *_rx_dma(). Handle IIR steering
in the irq handler with handle_rx_dma() helper.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250.h

@@ -17,7 +17,7 @@
 
 struct uart_8250_dma {
 	int (*tx_dma)(struct uart_8250_port *p);
-	int (*rx_dma)(struct uart_8250_port *p, unsigned int iir);
+	int (*rx_dma)(struct uart_8250_port *p);
 
 	/* Filter function */
 	dma_filter_fn		fn;
@@ -189,7 +189,8 @@ static inline int is_omap1510_8250(struct uart_8250_port *pt)
 
 #ifdef CONFIG_SERIAL_8250_DMA
 extern int serial8250_tx_dma(struct uart_8250_port *);
-extern int serial8250_rx_dma(struct uart_8250_port *, unsigned int iir);
+extern int serial8250_rx_dma(struct uart_8250_port *);
+extern void serial8250_rx_dma_flush(struct uart_8250_port *);
 extern int serial8250_request_dma(struct uart_8250_port *);
 extern void serial8250_release_dma(struct uart_8250_port *);
 #else
@@ -197,10 +198,11 @@ static inline int serial8250_tx_dma(struct uart_8250_port *p)
 {
 	return -1;
 }
-static inline int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
+static inline int serial8250_rx_dma(struct uart_8250_port *p)
 {
 	return -1;
 }
+static inline void serial8250_rx_dma_flush(struct uart_8250_port *p) { }
 static inline int serial8250_request_dma(struct uart_8250_port *p)
 {
 	return -1;

drivers/tty/serial/8250/8250_dma.c

@@ -110,30 +110,11 @@ int serial8250_tx_dma(struct uart_8250_port *p)
 	return ret;
 }
 
-int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
+int serial8250_rx_dma(struct uart_8250_port *p)
 {
 	struct uart_8250_dma		*dma = p->dma;
 	struct dma_async_tx_descriptor	*desc;
 
-	switch (iir & 0x3f) {
-	case UART_IIR_RLSI:
-		/* 8250_core handles errors and break interrupts */
-		return -EIO;
-	case UART_IIR_RX_TIMEOUT:
-		/*
-		 * If RCVR FIFO trigger level was not reached, complete the
-		 * transfer and let 8250_core copy the remaining data.
-		 */
-		if (dma->rx_running) {
-			dmaengine_pause(dma->rxchan);
-			__dma_rx_complete(p);
-			dmaengine_terminate_all(dma->rxchan);
-		}
-		return -ETIMEDOUT;
-	default:
-		break;
-	}
-
 	if (dma->rx_running)
 		return 0;
 
@@ -154,6 +135,17 @@ int serial8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 	return 0;
 }
 
+void serial8250_rx_dma_flush(struct uart_8250_port *p)
+{
+	struct uart_8250_dma *dma = p->dma;
+
+	if (dma->rx_running) {
+		dmaengine_pause(dma->rxchan);
+		__dma_rx_complete(p);
+		dmaengine_terminate_all(dma->rxchan);
+	}
+}
+
 int serial8250_request_dma(struct uart_8250_port *p)
 {
 	struct uart_8250_dma	*dma = p->dma;

drivers/tty/serial/8250/8250_omap.c

@@ -115,6 +115,12 @@ struct omap8250_priv {
 	bool rx_dma_broken;
 };
 
+#ifdef CONFIG_SERIAL_8250_DMA
+static void omap_8250_rx_dma_flush(struct uart_8250_port *p);
+#else
+static inline void omap_8250_rx_dma_flush(struct uart_8250_port *p) { }
+#endif
+
 static u32 uart_read(struct uart_8250_port *up, u32 reg)
 {
 	return readl(up->port.membase + (reg << up->port.regshift));
@@ -635,7 +641,7 @@ static int omap_8250_startup(struct uart_port *port)
 	serial_out(up, UART_OMAP_WER, priv->wer);
 
 	if (up->dma)
-		up->dma->rx_dma(up, 0);
+		up->dma->rx_dma(up);
 
 	pm_runtime_mark_last_busy(port->dev);
 	pm_runtime_put_autosuspend(port->dev);
@@ -654,7 +660,7 @@ static void omap_8250_shutdown(struct uart_port *port)
 
 	flush_work(&priv->qos_work);
 	if (up->dma)
-		up->dma->rx_dma(up, UART_IIR_RX_TIMEOUT);
+		omap_8250_rx_dma_flush(up);
 
 	pm_runtime_get_sync(port->dev);
 
@@ -742,7 +748,7 @@ static void omap_8250_unthrottle(struct uart_port *port)
 }
 
 #ifdef CONFIG_SERIAL_8250_DMA
-static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir);
+static int omap_8250_rx_dma(struct uart_8250_port *p);
 
 static void __dma_rx_do_complete(struct uart_8250_port *p)
 {
@@ -778,7 +784,7 @@ static void __dma_rx_do_complete(struct uart_8250_port *p)
 static void __dma_rx_complete(void *param)
 {
 	__dma_rx_do_complete(param);
-	omap_8250_rx_dma(param, 0);
+	omap_8250_rx_dma(param);
 }
 
 static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
@@ -804,7 +810,7 @@ static void omap_8250_rx_dma_flush(struct uart_8250_port *p)
 	__dma_rx_do_complete(p);
 }
 
-static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
+static int omap_8250_rx_dma(struct uart_8250_port *p)
 {
 	struct omap8250_priv		*priv = p->port.private_data;
 	struct uart_8250_dma            *dma = p->dma;
@@ -812,35 +818,6 @@ static int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
 	struct dma_async_tx_descriptor  *desc;
 	unsigned long			flags;
 
-	switch (iir & 0x3f) {
-	case UART_IIR_RLSI:
-		/* 8250_core handles errors and break interrupts */
-		omap_8250_rx_dma_flush(p);
-		return -EIO;
-	case UART_IIR_RX_TIMEOUT:
-		/*
-		 * If RCVR FIFO trigger level was not reached, complete the
-		 * transfer and let 8250_core copy the remaining data.
-		 */
-		omap_8250_rx_dma_flush(p);
-		return -ETIMEDOUT;
-	case UART_IIR_RDI:
-		/*
-		 * The OMAP UART is a special BEAST. If we receive RDI we _have_
-		 * a DMA transfer programmed but it didn't work. One reason is
-		 * that we were too slow and there were too many bytes in the
-		 * FIFO, the UART counted wrong and never kicked the DMA engine
-		 * to do anything. That means once we receive RDI on OMAP then
-		 * the DMA won't do anything soon so we have to cancel the DMA
-		 * transfer and purge the FIFO manually.
-		 */
-		omap_8250_rx_dma_flush(p);
-		return -ETIMEDOUT;
-
-	default:
-		break;
-	}
-
 	if (priv->rx_dma_broken)
 		return -EINVAL;
 
@@ -1014,6 +991,18 @@ static int omap_8250_tx_dma(struct uart_8250_port *p)
 	return ret;
 }
 
+static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
+{
+	switch (iir & 0x3f) {
+	case UART_IIR_RLSI:
+	case UART_IIR_RX_TIMEOUT:
+	case UART_IIR_RDI:
+		omap_8250_rx_dma_flush(up);
+		return true;
+	}
+	return omap_8250_rx_dma(up);
+}
+
 /*
  * This is mostly serial8250_handle_irq(). We have a slightly different DMA
  * hoook for RX/TX and need different logic for them in the ISR. Therefore we
@@ -1039,9 +1028,9 @@ static int omap_8250_dma_handle_irq(struct uart_port *port)
 	status = serial_port_in(port, UART_LSR);
 
 	if (status & (UART_LSR_DR | UART_LSR_BI)) {
-		if (omap_8250_rx_dma(up, iir)) {
+		if (handle_rx_dma(up, iir)) {
 			status = serial8250_rx_chars(up, status);
-			omap_8250_rx_dma(up, 0);
+			omap_8250_rx_dma(up);
 		}
 	}
 	serial8250_modem_status(up);
@@ -1072,7 +1061,7 @@ static bool the_no_dma_filter_fn(struct dma_chan *chan, void *param)
 
 #else
 
-static inline int omap_8250_rx_dma(struct uart_8250_port *p, unsigned int iir)
+static inline int omap_8250_rx_dma(struct uart_8250_port *p)
 {
 	return -EINVAL;
 }
@@ -1383,7 +1372,7 @@ static int omap8250_runtime_suspend(struct device *dev)
 	}
 
 	if (up->dma && up->dma->rxchan)
-		omap_8250_rx_dma(up, UART_IIR_RX_TIMEOUT);
+		omap_8250_rx_dma_flush(up);
 
 	priv->latency = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE;
 	schedule_work(&priv->qos_work);
@@ -1406,7 +1395,7 @@ static int omap8250_runtime_resume(struct device *dev)
 		omap8250_restore_regs(up);
 
 	if (up->dma && up->dma->rxchan)
-		omap_8250_rx_dma(up, 0);
+		omap_8250_rx_dma(up);
 
 	priv->latency = priv->calc_latency;
 	schedule_work(&priv->qos_work);

drivers/tty/serial/8250/8250_port.c

@@ -1788,6 +1788,18 @@ unsigned int serial8250_modem_status(struct uart_8250_port *up)
 }
 EXPORT_SYMBOL_GPL(serial8250_modem_status);
 
+static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
+{
+	switch (iir & 0x3f) {
+	case UART_IIR_RX_TIMEOUT:
+		serial8250_rx_dma_flush(up);
+		/* fall-through */
+	case UART_IIR_RLSI:
+		return true;
+	}
+	return up->dma->rx_dma(up);
+}
+
 /*
  * This handles the interrupt from one port.
  */
@@ -1807,7 +1819,7 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir)
 	DEBUG_INTR("status = %x...", status);
 
 	if (status & (UART_LSR_DR | UART_LSR_BI)) {
-		if (!up->dma || up->dma->rx_dma(up, iir))
+		if (!up->dma || handle_rx_dma(up, iir))
 			status = serial8250_rx_chars(up, status);
 	}
 	serial8250_modem_status(up);