Re: [PATCH v3 2/2] watchdog: Add Nuvoton NPCM watchdog driver

From: Guenter Roeck
Date: Fri Mar 09 2018 - 09:40:06 EST

On 03/08/2018 08:51 PM, Joel Stanley wrote:
The Nuvoton NPCM750 has a watchdog implemented as a single register
inside the timer peripheral.

This driver exposes that watchdog as a standard watchdog device with
coarse timeout intervals, limited by the combination of prescaler and
counter that is provided by the hardware. The calculation is taken from
the Nuvoton vendor tree.

The watchdog is left running if a bootloader had it going. The rate is
the one specified in the device tree, or the default value (obtained
from the datasheet).

There is a pre-timeout IRQ that is wired up. This timeout always occurs
1024 clocks before the timeout.

Signed-off-by: Joel Stanley <joel@xxxxxxxxx>
---
v2:
- Make MODULE_LICENCE gpl v2 to match SPDX
- Remove unused struct device pointer
- Remove unused setting of drvdata
- Add linux/bitops.h
- Sort includes
- Remove unused fiq include
- Update timeout with achieved value
v3:
- Calculate the time and register value seperately
- Pass device tree value through set_timeout to ensure it can
be represented by hardware
---
drivers/watchdog/Kconfig | 11 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/npcm_wdt.c | 254 ++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 266 insertions(+)
create mode 100644 drivers/watchdog/npcm_wdt.c

diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index aff773bcebdb..0c1cc68894e6 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -513,6 +513,17 @@ config COH901327_WATCHDOG
This watchdog is used to reset the system and thus cannot be
compiled as a module.
+config NPCM750_WATCHDOG
+ bool "NPCM750 watchdog"
+ depends on ARCH_NPCM || COMPILE_TEST
+ default y if ARCH_NPCM750
+ select WATCHDOG_CORE
+ help
+ Say Y here to include Watchdog timer support for the
+ watchdog embedded into the NPCM750.
+ This watchdog is used to reset the system and thus cannot be
+ compiled as a module.
+
config TWL4030_WATCHDOG
tristate "TWL4030 Watchdog"
depends on TWL4030_CORE
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index 0474d38aa854..97a5afb5cad2 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -61,6 +61,7 @@ obj-$(CONFIG_ORION_WATCHDOG) += orion_wdt.o
obj-$(CONFIG_SUNXI_WATCHDOG) += sunxi_wdt.o
obj-$(CONFIG_RN5T618_WATCHDOG) += rn5t618_wdt.o
obj-$(CONFIG_COH901327_WATCHDOG) += coh901327_wdt.o
+obj-$(CONFIG_NPCM7XX_WATCHDOG) += npcm_wdt.o
obj-$(CONFIG_STMP3XXX_RTC_WATCHDOG) += stmp3xxx_rtc_wdt.o
obj-$(CONFIG_NUC900_WATCHDOG) += nuc900_wdt.o
obj-$(CONFIG_TS4800_WATCHDOG) += ts4800_wdt.o
diff --git a/drivers/watchdog/npcm_wdt.c b/drivers/watchdog/npcm_wdt.c
new file mode 100644
index 000000000000..723f80ebf100
--- /dev/null
+++ b/drivers/watchdog/npcm_wdt.c
@@ -0,0 +1,254 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2018 Nuvoton Technology corporation.
+// Copyright (c) 2018 IBM Corp.
+
+#include <linux/bitops.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+#include <linux/watchdog.h>
+
+#define NPCM_WTCR 0x1C
+
+#define NPCM_WTCLK (BIT(10) | BIT(11)) /* Clock divider */
+#define NPCM_WTE BIT(7) /* Enable */
+#define NPCM_WTIE BIT(6) /* Enable irq */
+#define NPCM_WTIS (BIT(4) | BIT(5)) /* Interval selection */
+#define NPCM_WTIF BIT(3) /* Interrupt flag*/
+#define NPCM_WTRF BIT(2) /* Reset flag */
+#define NPCM_WTRE BIT(1) /* Reset enable */
+#define NPCM_WTR BIT(0) /* Reset counter */
+
+/*
+ * Watchdog timeouts
+ *
+ * 170 msec: WTCLK=01 WTIS=00 VAL= 0x400
+ * 670 msec: WTCLK=01 WTIS=01 VAL= 0x410
+ * 1360 msec: WTCLK=10 WTIS=00 VAL= 0x800
+ * 2700 msec: WTCLK=01 WTIS=10 VAL= 0x420
+ * 5360 msec: WTCLK=10 WTIS=01 VAL= 0x810
+ * 10700 msec: WTCLK=01 WTIS=11 VAL= 0x430
+ * 21600 msec: WTCLK=10 WTIS=10 VAL= 0x820
+ * 43000 msec: WTCLK=11 WTIS=00 VAL= 0xC00
+ * 85600 msec: WTCLK=10 WTIS=11 VAL= 0x830
+ * 172000 msec: WTCLK=11 WTIS=01 VAL= 0xC10
+ * 687000 msec: WTCLK=11 WTIS=10 VAL= 0xC20
+ * 2750000 msec: WTCLK=11 WTIS=11 VAL= 0xC30
+ */
+
+struct npcm_wdt {
+ struct watchdog_device wdd;
+ void __iomem *reg;
+};
+
+static inline struct npcm_wdt *to_npcm_wdt(struct watchdog_device *wdd)
+{
+ return container_of(wdd, struct npcm_wdt, wdd);
+}
+
+static int npcm_wdt_ping(struct watchdog_device *wdd)
+{
+ struct npcm_wdt *wdt = to_npcm_wdt(wdd);
+ u32 val;
+
+ val = readl(wdt->reg);
+ writel(val | NPCM_WTR, wdt->reg);
+
+ return 0;
+}
+
+static int npcm_wdt_start(struct watchdog_device *wdd)
+{
+ struct npcm_wdt *wdt = to_npcm_wdt(wdd);
+ u32 val;
+
+ if (wdd->timeout < 2)
+ val = 0x800;
+ else if (wdd->timeout < 3)
+ val = 0x420;
+ else if (wdd->timeout < 6)
+ val = 0x810;
+ else if (wdd->timeout < 11)
+ val = 0x430;
+ else if (wdd->timeout < 22)
+ val = 0x820;
+ else if (wdd->timeout < 44)
+ val = 0xC00;
+ else if (wdd->timeout < 87)
+ val = 0x830;
+ else if (wdd->timeout < 173)
+ val = 0xC10;
+ else if (wdd->timeout < 688)
+ val = 0xC20;
+ else
+ val = 0xC30;
+
+ val |= NPCM_WTRE | NPCM_WTE | NPCM_WTR | NPCM_WTIE;
+
+ writel(val, wdt->reg);
+
+ return 0;
+}
+
+static int npcm_wdt_stop(struct watchdog_device *wdd)
+{
+ struct npcm_wdt *wdt = to_npcm_wdt(wdd);
+
+ writel(0, wdt->reg);
+
+ return 0;
+}
+
+
+static int npcm_wdt_set_timeout(struct watchdog_device *wdd,
+ unsigned int timeout)
+{
+ if (timeout < 2)
+ wdd->timeout = 1;
+ else if (timeout < 3)
+ wdd->timeout = 2;
+ else if (timeout < 6)
+ wdd->timeout = 5;
+ else if (timeout < 11)
+ wdd->timeout = 10;
+ else if (timeout < 22)
+ wdd->timeout = 21;
+ else if (timeout < 44)
+ wdd->timeout = 43;
+ else if (timeout < 87)
+ wdd->timeout = 86;
+ else if (timeout < 173)
+ wdd->timeout = 172;
+ else if (timeout < 688)
+ wdd->timeout = 687;
+ else
+ wdd->timeout = 2750;
+
+ if (watchdog_active(wdd))
+ npcm_wdt_start(wdd);
+
+ return 0;
+}
+
+static irqreturn_t npcm_wdt_interrupt(int irq, void *data)
+{
+ struct npcm_wdt *wdt = data;
+
+ watchdog_notify_pretimeout(&wdt->wdd);
+
+ return IRQ_HANDLED;
+}
+
+static int npcm_wdt_restart(struct watchdog_device *wdd,
+ unsigned long action, void *data)
+{
+ struct npcm_wdt *wdt = to_npcm_wdt(wdd);
+
+ writel(NPCM_WTR | NPCM_WTRE | NPCM_WTE, wdt->reg);
+ udelay(1000);
+
+ return 0;
+}
+
+static bool npcm_is_running(struct watchdog_device *wdd)
+{
+ struct npcm_wdt *wdt = to_npcm_wdt(wdd);
+
+ return readl(wdt->reg) & NPCM_WTE;
+}
+
+static const struct watchdog_info npcm_wdt_info = {
+ .identity = KBUILD_MODNAME,
+ .options = WDIOF_SETTIMEOUT
+ | WDIOF_KEEPALIVEPING
+ | WDIOF_MAGICCLOSE,
+};
+
+static const struct watchdog_ops npcm_wdt_ops = {
+ .owner = THIS_MODULE,
+ .start = npcm_wdt_start,
+ .stop = npcm_wdt_stop,
+ .ping = npcm_wdt_ping,
+ .set_timeout = npcm_wdt_set_timeout,
+ .restart = npcm_wdt_restart,
+};
+
+static int npcm_wdt_probe(struct platform_device *pdev)
+{
+ struct device *dev = &pdev->dev;
+ struct npcm_wdt *wdt;
+ struct resource *res;
+ int irq;
+ int ret;
+
+ wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+ if (!wdt)
+ return -ENOMEM;
+
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ wdt->reg = devm_ioremap_resource(dev, res);
+ if (IS_ERR(wdt->reg))
+ return PTR_ERR(wdt->reg);
+
+ irq = platform_get_irq(pdev, 0);
+ if (!irq)
+ return -EINVAL;
+

Sorry for not noticing this earlier. platform_get_irq() returns a negative error value,
and you'll want to return that error because it could be -EPROBE_DEFER.

+ wdt->wdd.info = &npcm_wdt_info;
+ wdt->wdd.ops = &npcm_wdt_ops;
+ wdt->wdd.min_timeout = 1;
+ wdt->wdd.max_timeout = 2750;
+ wdt->wdd.parent = dev;
+
+ wdt->wdd.timeout = 86;
+ watchdog_init_timeout(&wdt->wdd, 0, dev);
+
+ /* Ensure timeout is able to be represented by the hardware */
+ npcm_wdt_set_timeout(&wdt->wdd, wdt->wdd.timeout);
+
+ if (npcm_is_running(&wdt->wdd)) {
+ /* Restart with the default or device-tree specified timeout */
+ npcm_wdt_start(&wdt->wdd);
+ set_bit(WDOG_HW_RUNNING, &wdt->wdd.status);
+ }
+
+ ret = devm_request_irq(dev, irq, npcm_wdt_interrupt, 0,
+ "watchdog", wdt);

Alignment ?

+ if (ret)
+ return ret;
+
+ ret = devm_watchdog_register_device(dev, &wdt->wdd);
+ if (ret) {
+ dev_err(dev, "failed to register watchdog\n");
+ return ret;
+ }
+
+ dev_info(dev, "NPCM watchdog driver enabled\n");
+
+ return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id npcm_wdt_match[] = {
+ {.compatible = "nuvoton,npcm750-wdt"},
+ {},
+};
+MODULE_DEVICE_TABLE(of, npcm_wdt_match);
+#endif
+
+static struct platform_driver npcm_wdt_driver = {
+ .probe = npcm_wdt_probe,
+ .driver = {
+ .name = "npcm-wdt",
+ .of_match_table = of_match_ptr(npcm_wdt_match),
+ },
+};
+module_platform_driver(npcm_wdt_driver);
+
+MODULE_AUTHOR("Joel Stanley");
+MODULE_DESCRIPTION("Watchdog driver for NPCM");
+MODULE_LICENSE("GPL v2");