[PATCH v3 3/5] watchdog: ts4800: add driver for TS-4800 watchdog

From: Damien Riegel
Date: Mon Nov 16 2015 - 14:17:30 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.

This watchdog is present on several of Technologic Systems' boards, and
having a kernel driver allows to use these boards without relying on a
userspace tool to ping their watchdog.

Signed-off-by: Damien Riegel <damien.riegel@xxxxxxxxxxxxxxxxxxxx>
---
.../devicetree/bindings/watchdog/ts4800-wdt.txt | 21 ++
drivers/watchdog/Kconfig | 10 +
drivers/watchdog/Makefile | 1 +
drivers/watchdog/ts4800_wdt.c | 219 +++++++++++++++++++++
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..7d5dcfb
--- /dev/null
+++ b/Documentation/devicetree/bindings/watchdog/ts4800-wdt.txt
@@ -0,0 +1,21 @@
+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
+
+Example:
+
+syscon: syscon@b0010000 {
+ compatible = "syscon", "simple-mfd";
+ reg = <0xb0010000 0x3d>;
+ bus-width = <16>;
+
+ wdt@e {
+ compatible = "technologic,ts4800-wdt";
+ syscon = <&syscon 0xe>;
+ };
+}
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 79e1aa1..2914594 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 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..658d0ca
--- /dev/null
+++ b/drivers/watchdog/ts4800_wdt.c
@@ -0,0 +1,219 @@
+/*
+ * 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;
+ u16 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 },
+};
+
+static int timeout_to_regval(struct watchdog_device *wdd, int new_timeout)
+{
+ int i;
+
+ new_timeout = clamp_val(new_timeout,
+ wdd->min_timeout, wdd->max_timeout);
+
+ for (i = 0; i < ARRAY_SIZE(ts4800_wdt_map); i++) {
+ if (ts4800_wdt_map[i].timeout >= new_timeout)
+ return ts4800_wdt_map[i].timeout;
+ }
+
+ return -EINVAL;
+}
+
+static void ts4800_write_feed(struct ts4800_wdt *wdt, u16 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 new_timeout)
+{
+ struct ts4800_wdt *wdt = watchdog_get_drvdata(wdd);
+ int val = timeout_to_regval(wdd, new_timeout);
+
+ if (val < 0)
+ return val;
+
+ wdt->feed_val = (u16) val;
+
+ 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)
+{
+ const int max_timeout_index = ARRAY_SIZE(ts4800_wdt_map) - 1;
+ 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 -EINVAL;
+ }
+
+ /* 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 (!wdt->regmap) {
+ dev_err(&pdev->dev, "cannot get parent's regmap\n");
+ return -EINVAL;
+ }
+
+ /* 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;
+ wdd->timeout = wdd->max_timeout;
+ wdt->feed_val = ts4800_wdt_map[max_timeout_index].regval;
+
+ watchdog_set_drvdata(wdd, wdt);
+ watchdog_set_nowayout(wdd, nowayout);
+
+ /*
+ * Must be called after watchdog_set_drvdata to dereference a valid
+ * pointer. The feed register is write-only, so it is not possible to
+ * determine if watchdog is already started or not. 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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