[PATCH v8] watchdog: ts4800: add driver for TS-4800 watchdog

From: Damien Riegel
Date: Tue Dec 08 2015 - 11:38:05 EST

This watchdog is instantiated in a FPGA that is memory mapped. It 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.

It is part of a syscon block, and the watchdog register offset in this
block varies from board to board. This offset is passed in the syscon
property after the phandle to the syscon node.

Signed-off-by: Damien Riegel <damien.riegel@xxxxxxxxxxxxxxxxxxxx>
Acked-by: Rob Herring <robh@xxxxxxxxxx>
Reviewed-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
Changes in v8:
- Split the serie into two parts: watchdog and dts as there are no
build dependencies between the two
- Added Reviewed-by Guenter Roeck and Acked-by by Rob Herring (for
the dts bindings).

Changes in v7:
- syscon: change bus-width DT property to reg-io-width
- watchdog: add dependency on HAS_IOMEM (spotted by a 0-day build)

Changes in v6:
- vendor prefix: reorder to sort alphabetically (wrong order since v3)
- split commit adding device tree into two patches: one for the doc, one for
the bindings

Changes in v5:
- watchdog: changed iteration stop condition in set_timeout to be less
error prone

Changes in v4:
- syscon: rewrite DT property reading to be clearer
- watchdog: made fixes suggested by Guenter (now uses
watchdog_init_timeout, u32 instead of u16, fixed error checking in
probe, cleaned set_timeout)

Changes in v3:
- Rebased on v4.3
- Changed vendor prefix from "ts" to "technologic"
- Added a DT option to generic syscon driver to allow regmap configuration
- Dropped custom mfd driver, use generic syscon driver instead.

Changes in v2:
- Added a mfd driver to handle syscon registers
- The watchdog driver now uses the regmap (created by the mfd driver)
to access the feed register
- Remove watchdog's dependency on SOC_IMX51

.../devicetree/bindings/watchdog/ts4800-wdt.txt | 25 +++
drivers/watchdog/Kconfig | 10 +
drivers/watchdog/Makefile | 1 +
drivers/watchdog/ts4800_wdt.c | 215 +++++++++++++++++++++
4 files changed, 251 insertions(+)
create mode 100644 Documentation/devicetree/bindings/watchdog/ts4800-wdt.txt
create mode 100644 drivers/watchdog/ts4800_wdt.c

diff --git a/Documentation/devicetree/bindings/watchdog/ts4800-wdt.txt b/Documentation/devicetree/bindings/watchdog/ts4800-wdt.txt
new file mode 100644
index 0000000..8f6caad
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/ts4800-wdt.txt
@@ -0,0 +1,25 @@
+Technologic Systems Watchdog
+
+Required properties:
+- compatible: must be "technologic,ts4800-wdt"
+- syscon: phandle / integer array that points to the syscon node which
+ describes the FPGA's syscon registers.
+ - phandle to FPGA's syscon
+ - offset to the watchdog register
+
+Optional property:
+- timeout-sec: contains the watchdog timeout in seconds.
+
+Example:
+
+syscon: syscon@b0010000 {
+ compatible = "syscon", "simple-mfd";
+ reg = <0xb0010000 0x3d>;
+ reg-io-width = <2>;
+
+ wdt@e {
+ compatible = "technologic,ts4800-wdt";
+ syscon = <&syscon 0xe>;
+ timeout-sec = <10>;
+ };
+}
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 79e1aa1..bb624d2 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -426,6 +426,16 @@ config NUC900_WATCHDOG
To compile this driver as a module, choose M here: the
module will be called nuc900_wdt.

+config TS4800_WATCHDOG
+ tristate "TS-4800 Watchdog"
+ depends on HAS_IOMEM && OF
+ select WATCHDOG_CORE
+ select MFD_SYSCON
+ help
+ Technologic Systems TS-4800 has watchdog timer implemented in
+ an external FPGA. Say Y here if you want to support for the
+ watchdog timer on TS-4800 board.
+
config TS72XX_WATCHDOG
tristate "TS-72XX SBC Watchdog"
depends on MACH_TS72XX
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 0c616e3..3863ce0 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -53,6 +53,7 @@ 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-$(CONFIG_TS4800_WATCHDOG) += ts4800_wdt.o
obj-$(CONFIG_TS72XX_WATCHDOG) += ts72xx_wdt.o
obj-$(CONFIG_IMX2_WDT) += imx2_wdt.o
obj-$(CONFIG_UX500_WATCHDOG) += ux500_wdt.o
diff --git a/drivers/watchdog/ts4800_wdt.c b/drivers/watchdog/ts4800_wdt.c
new file mode 100644
index 0000000..2b8de86
--- /dev/null
+++ b/drivers/watchdog/ts4800_wdt.c
@@ -0,0 +1,215 @@
+/*
+ * Watchdog driver for TS-4800 based boards
+ *
+ * Copyright (c) 2015 - Savoir-faire Linux
+ *
+ * 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.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 TS4800_WDT_FEED_2S 0x1
+#define TS4800_WDT_FEED_10S 0x2
+#define TS4800_WDT_DISABLE 0x3
+
+struct ts4800_wdt {
+ struct watchdog_device wdd;
+ struct regmap *regmap;
+ u32 feed_offset;
+ u32 feed_val;
+};
+
+/*
+ * TS-4800 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;
+} ts4800_wdt_map[] = {
+ { 2, TS4800_WDT_FEED_2S },
+ { 10, TS4800_WDT_FEED_10S },
+};
+
+#define MAX_TIMEOUT_INDEX (ARRAY_SIZE(ts4800_wdt_map) - 1)
+
+static void ts4800_write_feed(struct ts4800_wdt *wdt, u32 val)
+{
+ regmap_write(wdt->regmap, wdt->feed_offset, val);
+}
+
+static int ts4800_wdt_start(struct watchdog_device *wdd)
+{
+ struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
+
+ ts4800_write_feed(wdt, wdt->feed_val);
+ return 0;
+}
+
+static int ts4800_wdt_stop(struct watchdog_device *wdd)
+{
+ struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
+
+ ts4800_write_feed(wdt, TS4800_WDT_DISABLE);
+ return 0;
+}
+
+static int ts4800_wdt_set_timeout(struct watchdog_device *wdd,
+ unsigned int timeout)
+{
+ struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
+ int i;
+
+ for (i = 0; i < MAX_TIMEOUT_INDEX; i++) {
+ if (ts4800_wdt_map[i].timeout >= timeout)
+ break;
+ }
+
+ wdd->timeout = ts4800_wdt_map[i].timeout;
+ wdt->feed_val = ts4800_wdt_map[i].regval;
+
+ return 0;
+}
+
+static const struct watchdog_ops ts4800_wdt_ops = {
+ .owner = THIS_MODULE,
+ .start = ts4800_wdt_start,
+ .stop = ts4800_wdt_stop,
+ .set_timeout = ts4800_wdt_set_timeout,
+};
+
+static const struct watchdog_info ts4800_wdt_info = {
+ .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
+ .identity = "TS-4800 Watchdog",
+};
+
+static int ts4800_wdt_probe(struct platform_device *pdev)
+{
+ struct device_node *np = pdev->dev.of_node;
+ struct device_node *syscon_np;
+ struct watchdog_device *wdd;
+ struct ts4800_wdt *wdt;
+ u32 reg;
+ int ret;
+
+ syscon_np = of_parse_phandle(np, "syscon", 0);
+ if (!syscon_np) {
+ dev_err(&pdev->dev, "no syscon property\n");
+ return -ENODEV;
+ }
+
+ ret = of_property_read_u32_index(np, "syscon", 1, &reg);
+ if (ret < 0) {
+ dev_err(&pdev->dev, "no offset in syscon\n");
+ return ret;
+ }
+
+ /* allocate memory for watchdog struct */
+ wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+ if (!wdt)
+ return -ENOMEM;
+
+ /* set regmap and offset to know where to write */
+ wdt->feed_offset = reg;
+ wdt->regmap = syscon_node_to_regmap(syscon_np);
+ if (IS_ERR(wdt->regmap)) {
+ dev_err(&pdev->dev, "cannot get parent's regmap\n");
+ return PTR_ERR(wdt->regmap);
+ }
+
+ /* Initialize struct watchdog_device */
+ wdd = &wdt->wdd;
+ wdd->parent = &pdev->dev;
+ wdd->info = &ts4800_wdt_info;
+ wdd->ops = &ts4800_wdt_ops;
+ wdd->min_timeout = ts4800_wdt_map[0].timeout;
+ wdd->max_timeout = ts4800_wdt_map[MAX_TIMEOUT_INDEX].timeout;
+
+ watchdog_set_drvdata(wdd, wdt);
+ watchdog_set_nowayout(wdd, nowayout);
+ watchdog_init_timeout(wdd, 0, &pdev->dev);
+
+ /*
+ * As this watchdog supports only a few values, ts4800_wdt_set_timeout
+ * must be called to initialize timeout and feed_val with valid values.
+ * Default to maximum timeout if none, or an invalid one, is provided in
+ * device tree.
+ */
+ if (!wdd->timeout)
+ wdd->timeout = wdd->max_timeout;
+ ts4800_wdt_set_timeout(wdd, wdd->timeout);
+
+ /*
+ * The feed register is write-only, so it is not possible to determine
+ * watchdog's state. Disable it to be in a known state.
+ */
+ ts4800_wdt_stop(wdd);
+
+ ret = watchdog_register_device(wdd);
+ if (ret) {
+ dev_err(&pdev->dev,
+ "failed to register watchdog device\n");
+ return ret;
+ }
+
+ platform_set_drvdata(pdev, wdt);
+
+ dev_info(&pdev->dev,
+ "initialized (timeout = %d sec, nowayout = %d)\n",
+ wdd->timeout, nowayout);
+
+ return 0;
+}
+
+static int ts4800_wdt_remove(struct platform_device *pdev)
+{
+ struct ts4800_wdt *wdt = platform_get_drvdata(pdev);
+
+ watchdog_unregister_device(&wdt->wdd);
+
+ return 0;
+}
+
+static const struct of_device_id ts4800_wdt_of_match[] = {
+ { .compatible = "technologic,ts4800-wdt", },
+ { },
+};
+MODULE_DEVICE_TABLE(of, ts4800_wdt_of_match);
+
+static struct platform_driver ts4800_wdt_driver = {
+ .probe = ts4800_wdt_probe,
+ .remove = ts4800_wdt_remove,
+ .driver = {
+ .name = "ts4800_wdt",
+ .of_match_table = ts4800_wdt_of_match,
+ },
+};
+
+module_platform_driver(ts4800_wdt_driver);
+
+MODULE_AUTHOR("Damien Riegel <damien.riegel@xxxxxxxxxxxxxxxxxxxx>");
+MODULE_LICENSE("GPL v2");
+MODULE_ALIAS("platform:ts4800_wdt");
--
2.5.0

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