This watchdog is instantiated in a FPGA and can only be access using a
GPIOs bit-banged bus, called the NBUS by Technologic Systems.
The watchdog is made of only one register, called the feed register.
Writing to this register will re-arm the watchdog for a given time (and
enable it if it was disable). It can be disabled by writing a special
value into it.
---
Changes v1 -> v2:
  - rebase on master
  - retrieve the ts_nbus instantiated by the parent node (suggested by
  Linus Walleij)
  - rename the wdt by watchdog in the device tree and in the
  documentation (suggested by Rob Herring)
  - add a dependency to the TS_NBUS driver in the Kconfig (suggested by
  Guenter Roeck)
  - simplify the set_timeout function (suggested by Guenter Roeck)
  - use the max_hw_heartbeat_ms callback instead of the max_timeout
  callback (suggested by Guenter Roeck)

Signed-off-by: Sebastien Bourdelin <redacted>
---
 .../devicetree/bindings/watchdog/ts4600-wdt.txt    |  16 ++
 arch/arm/boot/dts/imx28-ts4600-common.dtsi         |   5 +
 drivers/watchdog/Kconfig                           |  11 ++
 drivers/watchdog/Makefile                          |   1 +
 drivers/watchdog/ts4600_wdt.c                      | 217 +++++++++++++++++++++
 5 files changed, 250 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/watchdog/ts4600-wdt.txt
 create mode 100644 drivers/watchdog/ts4600_wdt.c

diff --git a/Documentation/devicetree/bindings/watchdog/ts4600-wdt.txt b/Documentation/devicetree/bindings/watchdog/ts4600-wdt.txt
new file mode 100644
index 000000000000..7de00ceae341
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/ts4600-wdt.txt

@@ -0,0 +1,16 @@
+TS-4600 Technologic Systems Watchdog
+
+Required properties:
+- compatible: must be "technologic,ts4600-wdt"
+- reg: offset to the FPGA's watchdog register
+
+Optional property:
+- timeout-sec: contains the watchdog timeout in seconds.
+
+Example:
+
+watchdog {
+	compatible = "technologic,ts4600-wdt";
+	reg = <0x2a>;
+	timeout-sec = <10>;
+};

diff --git a/arch/arm/boot/dts/imx28-ts4600-common.dtsi b/arch/arm/boot/dts/imx28-ts4600-common.dtsi
index c6282d5479de..092c2eed0fe7 100644
--- a/arch/arm/boot/dts/imx28-ts4600-common.dtsi
+++ b/arch/arm/boot/dts/imx28-ts4600-common.dtsi

@@ -116,6 +116,11 @@
 		ts-strobe-gpios = <&gpio0 25 GPIO_ACTIVE_HIGH>;
 		ts-ale-gpios    = <&gpio0 26 GPIO_ACTIVE_HIGH>;
 		ts-rdy-gpios    = <&gpio0 21 GPIO_ACTIVE_HIGH>;
+
+		watchdog at 2a {
+			compatible = "technologic,ts4600-wdt";
+			reg = <0x2a>;
+		};
 	};
 
 };

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index acb00b53a520..ab1355eefad1 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig

@@ -500,6 +500,17 @@ config NUC900_WATCHDOG
 	  To compile this driver as a module, choose M here: the
 	  module will be called nuc900_wdt.
 
+config TS4600_WATCHDOG
+	tristate "TS-4600 Watchdog"
+	depends on TS_NBUS
+	depends on HAS_IOMEM && OF
+	depends on SOC_IMX28 || COMPILE_TEST
+	select WATCHDOG_CORE
+	help
+	  Technologic Systems TS-4600 has watchdog timer implemented in
+	  an external FPGA. Say Y here if you want to support for the
+	  watchdog timer on TS-4600 board.
+
 config TS4800_WATCHDOG
 	tristate "TS-4800 Watchdog"
 	depends on HAS_IOMEM && OF

diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 0c3d35e3c334..d5e164d2b4cd 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile

@@ -61,6 +61,7 @@ obj-$(CONFIG_RN5T618_WATCHDOG) += rn5t618_wdt.o
 obj-$(CONFIG_COH901327_WATCHDOG) += coh901327_wdt.o
 obj-$(CONFIG_STMP3XXX_RTC_WATCHDOG) += stmp3xxx_rtc_wdt.o
 obj-$(CONFIG_NUC900_WATCHDOG) += nuc900_wdt.o
+obj-$(CONFIG_TS4600_WATCHDOG) += ts4600_wdt.o
 obj-$(CONFIG_TS4800_WATCHDOG) += ts4800_wdt.o
 obj-$(CONFIG_TS72XX_WATCHDOG) += ts72xx_wdt.o
 obj-$(CONFIG_IMX2_WDT) += imx2_wdt.o

diff --git a/drivers/watchdog/ts4600_wdt.c b/drivers/watchdog/ts4600_wdt.c
new file mode 100644
index 000000000000..d7bf6cc04986
--- /dev/null
+++ b/drivers/watchdog/ts4600_wdt.c

@@ -0,0 +1,217 @@
+/*
+ * Watchdog driver for TS-4600 based boards
+ *
+ * Copyright (c) 2016 - Savoir-faire Linux
+ * Author: Sebastien Bourdelin <sebastien.bourdelin@savoirfairelinux.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ *
+ * The watchdog on the TS-4600 based boards is in an FPGA and can only be
+ * accessed using a GPIO bit-banged bus called the NBUS by Technologic Systems.
+ * The logic for the watchdog is the same then for the TS-4800 SoM, only the way
+ * to access it change, therefore this driver is heavely based on the ts4800_wdt
+ * driver from Damien Riegel <damien.riegel@savoirfairelinux.com>.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/ts-nbus.h>
+#include <linux/watchdog.h>
+
+static bool nowayout = WATCHDOG_NOWAYOUT;
+module_param(nowayout, bool, 0);
+MODULE_PARM_DESC(nowayout,
+	"Watchdog cannot be stopped once started (default="
+	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
+
+/* possible feed values */
+#define TS4600_WDT_FEED_2S       0x1
+#define TS4600_WDT_FEED_10S      0x2
+#define TS4600_WDT_DISABLE       0x3
+
+struct ts4600_wdt {
+	struct watchdog_device  wdd;
+	struct ts_nbus		*ts_nbus;
+	u32                     feed_offset;
+	u32                     feed_val;
+};
+
+/*
+ * TS-4600 supports the following timeout values:
+ *
+ *   value desc
+ *   ---------------------
+ *     0    feed for 338ms
+ *     1    feed for 2.706s
+ *     2    feed for 10.824s
+ *     3    disable watchdog
+ *
+ * Keep the regmap/timeout map ordered by timeout
+ */
+static const struct {
+	const int timeout;
+	const int regval;
+} ts4600_wdt_map[] = {
+	{ 2,  TS4600_WDT_FEED_2S },
+	{ 10, TS4600_WDT_FEED_10S },
+};