4 files changed, 115 insertions, 0 deletions

diff --git a/drivers/tty/serial/8250_dw.c b/drivers/tty/serial/8250_dw.c
new file mode 100644
index 000000000000..e25782aeec7a
--- /dev/null
+++ b/drivers/tty/serial/8250_dw.c
@@ -0,0 +1,99 @@
+/*
+ * Synopsys DesignWare specific 8250 operations.
+ *
+ * Copyright 2011 Picochip, Jamie Iles.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * The Synopsys DesignWare 8250 has an extra feature whereby it detects if the
+ * LCR is written whilst busy.  If it is, then a busy detect interrupt is
+ * raised, the LCR needs to be rewritten and the uart status register read.
+ */
+#include <linux/io.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <linux/slab.h>
+
+struct dw8250_data {
+        int     last_lcr;
+};
+
+static void dw8250_serial_out(struct uart_port *p, int offset, int value)
+{
+        struct dw8250_data *d = p->private_data;
+
+        if (offset == UART_LCR)
+                d->last_lcr = value;
+
+        offset <<= p->regshift;
+        writeb(value, p->membase + offset);
+}
+
+static unsigned int dw8250_serial_in(struct uart_port *p, int offset)
+{
+        offset <<= p->regshift;
+
+        return readb(p->membase + offset);
+}
+
+static void dw8250_serial_out32(struct uart_port *p, int offset,
+                                int value)
+{
+        struct dw8250_data *d = p->private_data;
+
+        if (offset == UART_LCR)
+                d->last_lcr = value;
+
+        offset <<= p->regshift;
+        writel(value, p->membase + offset);
+}
+
+static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)
+{
+        offset <<= p->regshift;
+
+        return readl(p->membase + offset);
+}
+
+/* Offset for the DesignWare's UART Status Register. */
+#define UART_USR        0x1f
+
+static int dw8250_handle_irq(struct uart_port *p)
+{
+        struct dw8250_data *d = p->private_data;
+        unsigned int iir = p->serial_in(p, UART_IIR);
+
+        if (serial8250_handle_irq(p, iir)) {
+                return 1;
+        } else if ((iir & UART_IIR_BUSY) == UART_IIR_BUSY) {
+                /* Clear the USR and write the LCR again. */
+                (void)p->serial_in(p, UART_USR);
+                p->serial_out(p, d->last_lcr, UART_LCR);
+
+                return 1;
+        }
+
+        return 0;
+}
+
+int serial8250_use_designware_io(struct uart_port *up)
+{
+        up->private_data = kzalloc(sizeof(struct dw8250_data), GFP_KERNEL);
+        if (!up->private_data)
+                return -ENOMEM;
+
+        if (up->iotype == UPIO_MEM32) {
+                up->serial_out = dw8250_serial_out32;
+                up->serial_in = dw8250_serial_in32;
+        } else {
+                up->serial_out = dw8250_serial_out;
+                up->serial_in = dw8250_serial_in;
+        }
+        up->handle_irq = dw8250_handle_irq;
+
+        return 0;
+}
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index a9b307f582e1..d2d1cc2329b7 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -267,6 +267,13 @@ config SERIAL_8250_RM9K
           port hardware found on MIPS RM9122 and similar processors.
           If unsure, say N.
 
+config SERIAL_8250_DW
+        bool "Support for Synopsys DesignWare 8250 quirks"
+        depends on SERIAL_8250
+        help
+          Selecting this option will enable handling of the extra features
+          present in the Synopsys DesignWare APB UART.
+
 comment "Non-8250 serial port support"
 
 config SERIAL_AMBA_PL010
diff --git a/drivers/tty/serial/Makefile b/drivers/tty/serial/Makefile
index 78748136ccc8..7b59958f50ec 100644
--- a/drivers/tty/serial/Makefile
+++ b/drivers/tty/serial/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_SERIAL_8250_BOCA) += 8250_boca.o
 obj-$(CONFIG_SERIAL_8250_EXAR_ST16C554) += 8250_exar_st16c554.o
 obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o
 obj-$(CONFIG_SERIAL_8250_MCA) += 8250_mca.o
+obj-$(CONFIG_SERIAL_8250_DW) += 8250_dw.o
 obj-$(CONFIG_SERIAL_AMBA_PL010) += amba-pl010.o
 obj-$(CONFIG_SERIAL_AMBA_PL011) += amba-pl011.o
 obj-$(CONFIG_SERIAL_CLPS711X) += clps711x.o
diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h
index 1f05bbeac01e..09e2dbcd7ca3 100644
--- a/include/linux/serial_8250.h
+++ b/include/linux/serial_8250.h
@@ -86,5 +86,13 @@ int serial8250_handle_irq(struct uart_port *port, unsigned int iir);
 extern void serial8250_set_isa_configurator(void (*v)
                                         (int port, struct uart_port *up,
                                                 unsigned short *capabilities));
+#ifndef SERIAL_8250_DW
+extern int serial8250_use_designware_io(struct uart_port *up);
+#else
+static inline int serial8250_use_designware_io(struct uart_port *up)
+{
+        return -EIO;
+}
+#endif
 
 #endif