tty: serial8250: add helpers for the DesignWare 8250

The Synopsys DesignWare 8250 is an 8250 that has an extra interrupt that
gets raised when writing to the LCR when busy.  To handle this we need
special serial_out, serial_in and handle_irq methods.  Add a new
function serial8250_use_designware_io() that configures a uart_port with
these accessors.

Cc: Alan Cox <alan@linux.intel.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/tty/serial/8250_dw.c b/drivers/tty/serial/8250_dw.c
new file mode 100644 (file)
index 0000000..e25782a
--- /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 a9b307f582e183d5e01f321293636b59df15f9ec..d2d1cc2329b7449c28ee15438ca511d63a9077ee 100644 (file)
--- 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 78748136ccc8f1c746e866d89bb481a6547ff1cf..7b59958f50ecabcd3dc1c64ee9fc1cabbd07bca1 100644 (file)
--- 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 1f05bbeac01e3605b7e11bd544e3edc7483c474a..09e2dbcd7ca33e3389e5f88cb2e4128befe18ec0 100644 (file)
--- 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