1 files changed, 81 insertions, 0 deletions
diff --git a/drivers/tty/serial/8250/8250_fsl.c b/drivers/tty/serial/8250/8250_fsl.c
new file mode 100644
index 000000000..bb9571eed
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_fsl.c
@@ -0,0 +1,81 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+
+#include "8250.h"
+
+/*
+ * Freescale 16550 UART "driver", Copyright (C) 2011 Paul Gortmaker.
+ *
+ * This isn't a full driver; it just provides an alternate IRQ
+ * handler to deal with an errata.  Everything else is just
+ * using the bog standard 8250 support.
+ *
+ * We follow code flow of serial8250_default_handle_irq() but add
+ * a check for a break and insert a dummy read on the Rx for the
+ * immediately following IRQ event.
+ *
+ * We re-use the already existing "bug handling" lsr_saved_flags
+ * field to carry the "what we just did" information from the one
+ * IRQ event to the next one.
+ */
+
+int fsl8250_handle_irq(struct uart_port *port)
+{
+	unsigned char lsr, orig_lsr;
+	unsigned long flags;
+	unsigned int iir;
+	struct uart_8250_port *up = up_to_u8250p(port);
+
+	spin_lock_irqsave(&up->port.lock, flags);
+
+	iir = port->serial_in(port, UART_IIR);
+	if (iir & UART_IIR_NO_INT) {
+		spin_unlock_irqrestore(&up->port.lock, flags);
+		return 0;
+	}
+
+	/* This is the WAR; if last event was BRK, then read and return */
+	if (unlikely(up->lsr_saved_flags & UART_LSR_BI)) {
+		up->lsr_saved_flags &= ~UART_LSR_BI;
+		port->serial_in(port, UART_RX);
+		spin_unlock_irqrestore(&up->port.lock, flags);
+		return 1;
+	}
+
+	lsr = orig_lsr = up->port.serial_in(&up->port, UART_LSR);
+
+	/* Process incoming characters first */
+	if ((lsr & (UART_LSR_DR | UART_LSR_BI)) &&
+	    (up->ier & (UART_IER_RLSI | UART_IER_RDI))) {
+		lsr = serial8250_rx_chars(up, lsr);
+	}
+
+	/* Stop processing interrupts on input overrun */
+	if ((orig_lsr & UART_LSR_OE) && (up->overrun_backoff_time_ms > 0)) {
+		unsigned long delay;
+
+		up->ier = port->serial_in(port, UART_IER);
+		if (up->ier & (UART_IER_RLSI | UART_IER_RDI)) {
+			port->ops->stop_rx(port);
+		} else {
+			/* Keep restarting the timer until
+			 * the input overrun subsides.
+			 */
+			cancel_delayed_work(&up->overrun_backoff);
+		}
+
+		delay = msecs_to_jiffies(up->overrun_backoff_time_ms);
+		schedule_delayed_work(&up->overrun_backoff, delay);
+	}
+
+	serial8250_modem_status(up);
+
+	if (lsr & UART_LSR_THRE)
+		serial8250_tx_chars(up);
+
+	up->lsr_saved_flags = orig_lsr;
+	spin_unlock_irqrestore(&up->port.lock, flags);
+	return 1;
+}
+EXPORT_SYMBOL_GPL(fsl8250_handle_irq);