Re: [PATCH v3 2/5] drivers: watchdog: Add STM32 IWDG driver
From: Guenter Roeck
Date: Tue Mar 28 2017 - 23:15:27 EST
On 03/22/2017 08:04 AM, Yannick Fertre wrote:
This patch adds IWDG (Independent WatchDoG) support for STM32 platform.
Change-Id: Iab218745fc25566f12558fae7f52e2f8c21db74e
No gerrit tags, please.
Signed-off-by: Yannick FERTRE <yannick.fertre@xxxxxx>
---
drivers/watchdog/Kconfig | 11 ++
drivers/watchdog/Makefile | 1 +
drivers/watchdog/stm32_iwdg.c | 289 ++++++++++++++++++++++++++++++++++++++++++
3 files changed, 301 insertions(+)
create mode 100644 drivers/watchdog/stm32_iwdg.c
diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
index 52a70ee..d9745a5 100644
--- a/drivers/watchdog/Kconfig
+++ b/drivers/watchdog/Kconfig
@@ -744,6 +744,17 @@ config ZX2967_WATCHDOG
To compile this driver as a module, choose M here: the
module will be called zx2967_wdt.
+config STM32_WATCHDOG
+ tristate "STM32 Independent WatchDoG (IWDG) support"
+ depends on ARCH_STM32
+ select WATCHDOG_CORE
+ default y
+ help
+ Say Y here to include Watchdog timer support.
... for <pick your text>.
+
+ To compile this driver as a module, choose M here: the
+ module will be called stm32_iwdg.
+
# AVR32 Architecture
config AT32AP700X_WDT
diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
index a2126e2..a35e423 100644
--- a/drivers/watchdog/Makefile
+++ b/drivers/watchdog/Makefile
@@ -84,6 +84,7 @@ obj-$(CONFIG_ATLAS7_WATCHDOG) += atlas7_wdt.o
obj-$(CONFIG_RENESAS_WDT) += renesas_wdt.o
obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
obj-$(CONFIG_ZX2967_WATCHDOG) += zx2967_wdt.o
+obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
# AVR32 Architecture
obj-$(CONFIG_AT32AP700X_WDT) += at32ap700x_wdt.o
diff --git a/drivers/watchdog/stm32_iwdg.c b/drivers/watchdog/stm32_iwdg.c
new file mode 100644
index 0000000..507dfc4
--- /dev/null
+++ b/drivers/watchdog/stm32_iwdg.c
@@ -0,0 +1,289 @@
+/*
+ * Driver for STM32 Independent Watchdog
+ *
+ * Copyright (C) Yannick Fertre 2017
+ * Author: Yannick Fertre <yannick.fertre@xxxxxx>
+ *
+ * This driver is based on tegra_wdt.c
+ *
+ * License terms: GNU General Public License (GPL), version 2
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/iopoll.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/watchdog.h>
+
+/* minimum watchdog trigger timeout, in seconds */
+#define MIN_WDT_TIMEOUT 1
+
+/* IWDG registers */
+#define IWDG_KR 0x00 /* Key register */
+#define IWDG_PR 0x04 /* Prescaler Register */
+#define IWDG_RLR 0x08 /* ReLoad Register */
+#define IWDG_SR 0x0C /* Status Register */
+#define IWDG_WINR 0x10 /* Windows Register */
+
+/* IWDG_KR register bit mask */
+#define KR_KEY_RELOAD 0xAAAA /* reload counter enable */
+#define KR_KEY_ENABLE 0xCCCC /* peripheral enable */
+#define KR_KEY_EWA 0x5555 /* write access enable */
+#define KR_KEY_DWA 0x0000 /* write access disable */
+
+/* IWDG_PR register bit values */
+#define PR_4 0x00 /* prescaler set to 4 */
+#define PR_8 0x01 /* prescaler set to 8 */
+#define PR_16 0x02 /* prescaler set to 16 */
+#define PR_32 0x03 /* prescaler set to 32 */
+#define PR_64 0x04 /* prescaler set to 64 */
+#define PR_128 0x05 /* prescaler set to 128 */
+#define PR_256 0x06 /* prescaler set to 256 */
+
+/* IWDG_RLR register values */
+#define RLR_MAX 0xFFF /* max value supported by reload register */
+
+/* IWDG_SR register bit mask */
+#define FLAG_PVU BIT(0) /* Watchdog prescaler value update */
+#define FLAG_RVU BIT(1) /* Watchdog counter reload value update */
+
+/* set timeout to 100000 us */
+#define TIMEOUT_US 100000
+#define SLEEP_US 1000
+
+struct stm32_iwdg {
+ struct watchdog_device wdd;
+ struct device *dev;
+ void __iomem *regs;
+ struct clk *clk;
+ unsigned int rate;
+};
+
+static int heartbeat = MIN_WDT_TIMEOUT;
+module_param(heartbeat, int, 0x0);
+MODULE_PARM_DESC(heartbeat,
+ "Watchdog heartbeats in seconds. (default = "
+ __MODULE_STRING(WDT_HEARTBEAT) ")");
+
+static inline u32 reg_read(void __iomem *base, u32 reg)
+{
+ return readl_relaxed(base + reg);
+}
+
+static inline void reg_write(void __iomem *base, u32 reg, u32 val)
+{
+ writel_relaxed(val, base + reg);
+}
+
+static int stm32_iwdg_start(struct watchdog_device *wdd)
+{
+ struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
+ u32 val = FLAG_PVU | FLAG_RVU;
+ u32 reload;
+ int ret;
+
+ dev_dbg(wdt->dev, "%s\n", __func__);
+
+ /* prescaler fixed to 256 */
+ reload = (wdd->timeout * wdt->rate) / 256;
+ if (reload > RLR_MAX + 1) {
+ dev_err(wdt->dev,
+ "Watchdog doesn't support reload value: %d\n", reload);
+ return -EINVAL;
+ }
This should not happen if min_timeout and max_timeout are set properly.
+
+ /* enable watchdog */
+ reg_write(wdt->regs, IWDG_KR, KR_KEY_ENABLE);
+
+ /* set prescaler & reload registers */
+ reg_write(wdt->regs, IWDG_KR, KR_KEY_EWA);
+ reg_write(wdt->regs, IWDG_PR, PR_256); /* prescaler fix to 256 */
+ reg_write(wdt->regs, IWDG_RLR, reload - 1);
+
+ /* wait for the registers to be updated (max 100ms) */
+ ret = readl_relaxed_poll_timeout(wdt->regs + IWDG_SR, val,
+ !(val & (FLAG_PVU | FLAG_RVU)),
+ SLEEP_US, TIMEOUT_US);
+ if (ret) {
+ dev_err(wdt->dev,
+ "Fail to set prescaler or reload registers\n");
+ return -EINVAL;
Any reason for overriding the return value ?
+ }
+
+ /* reload watchdog */
+ reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
+
+ return 0;
+}
+
+static int stm32_iwdg_stop(struct watchdog_device *wdd)
+{
+ struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
+
+ if (watchdog_active(wdd)) {
+ dev_err(wdt->dev,
+ "Watchdog can't be stopped once started(no way out)\n");
+ return -EPERM;
The infrastructure takes care of this. Don't provide a stop function, and provide
the maximum hardware timeout.
+ }
+
+ return 0;
+}
+
+static int stm32_iwdg_ping(struct watchdog_device *wdd)
+{
+ struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
+
+ dev_dbg(wdt->dev, "%s\n", __func__);
+
+ reg_write(wdt->regs, IWDG_KR, KR_KEY_RELOAD);
+
+ return 0;
+}
+
+static int stm32_iwdg_set_timeout(struct watchdog_device *wdd,
+ unsigned int timeout)
+{
+ struct stm32_iwdg *wdt = watchdog_get_drvdata(wdd);
+
+ dev_dbg(wdt->dev, "%s timeout: %d sec\n", __func__, timeout);
+
+ wdd->timeout = timeout;
+
+ if (watchdog_active(wdd))
+ return stm32_iwdg_start(wdd);
+
+ return 0;
+}
+
+static const struct watchdog_info stm32_iwdg_info = {
+ .options = WDIOF_SETTIMEOUT |
+ WDIOF_MAGICCLOSE |
+ WDIOF_KEEPALIVEPING,
+ .identity = "STM32 Independent Watchdog",
+};
+
+static struct watchdog_ops stm32_iwdg_ops = {
+ .owner = THIS_MODULE,
+ .start = stm32_iwdg_start,
+ .stop = stm32_iwdg_stop,
+ .ping = stm32_iwdg_ping,
+ .set_timeout = stm32_iwdg_set_timeout,
+};
+
+static int stm32_iwdg_probe(struct platform_device *pdev)
+{
+ struct watchdog_device *wdd;
+ struct stm32_iwdg *wdt;
+ struct resource *res;
+ void __iomem *regs;
+ struct clk *clk;
+ int max_wdt_timeout;
+ int ret;
+
+ /* This is the timer base. */
+ res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+ regs = devm_ioremap_resource(&pdev->dev, res);
+ if (IS_ERR(regs)) {
+ dev_err(&pdev->dev, "Could not get resource\n");
+ return PTR_ERR(regs);
+ }
+
+ clk = devm_clk_get(&pdev->dev, NULL);
+ if (IS_ERR(clk)) {
+ dev_err(&pdev->dev, "Unable to get clock\n");
+ return PTR_ERR(clk);
+ }
+
+ ret = clk_prepare_enable(clk);
+ if (ret) {
+ dev_err(&pdev->dev, "Unable to prepare clock %p\n", clk);
+ return ret;
+ }
+
+ /*
+ * Allocate our watchdog driver data, which has the
+ * struct watchdog_device nested within it.
+ */
+ wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
+ if (!wdt) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ /* Initialize struct stm32_iwdg. */
+ wdt->regs = regs;
+ wdt->dev = &pdev->dev;
+ wdt->clk = clk;
+ /*
+ * iwdg is clocked by its own dedicated low-speed clock (LSI)
+ * at 32khz.
+ */
+ wdt->rate = 32 * 1024;
Why not clk_get_rate() ?
+
+ /* get max timeout & set heartbeat */
+ max_wdt_timeout = ((RLR_MAX + 1) * 256) / wdt->rate;
+ heartbeat = max_wdt_timeout;
What is the value of overwriting this variable ? Why don't you just use max_wdt_timeout,
and what is the point of making heartbeat configurable if you overwrite it anyway ?
I would suggest to use watchdog_init_timeout() to set optional non-default
timeout values, especially since this also enables getting the timeout value from
devicetree.
+
+ /* Initialize struct watchdog_device. */
+ wdd = &wdt->wdd;
+ wdd->timeout = heartbeat;
+ wdd->info = &stm32_iwdg_info;
+ wdd->ops = &stm32_iwdg_ops;
+ wdd->min_timeout = MIN_WDT_TIMEOUT;
+ wdd->max_timeout = max_wdt_timeout;
You might want to consider setting max_hw_heartbeat_ms instead and drop the stop function.
+ watchdog_set_drvdata(wdd, wdt);
+ watchdog_set_nowayout(wdd, true);
+
+ ret = watchdog_register_device(wdd);
+ if (ret) {
+ dev_err(&pdev->dev,
+ "failed to register watchdog device\n");
+ goto err;
+ }
+
+ platform_set_drvdata(pdev, wdt);
+
+ dev_info(&pdev->dev,
+ "initialized (heartbeat = %d sec)\n", heartbeat);
+ return 0;
+
+err:
+ clk_disable_unprepare(clk);
+ return ret;
+}
+
+static int stm32_iwdg_remove(struct platform_device *pdev)
+{
+ struct stm32_iwdg *wdt = platform_get_drvdata(pdev);
+
+ watchdog_unregister_device(&wdt->wdd);
+ clk_disable_unprepare(wdt->clk);
+
+ dev_info(&pdev->dev, "removed watchdog device\n");
Is this message really useful ? I think it is just noise.
+ return 0;
+}
+
+static const struct of_device_id stm32_iwdg_of_match[] = {
+ { .compatible = "st,stm32-iwdg" },
+ { /* end node */ }
+};
+MODULE_DEVICE_TABLE(of, stm32_iwdg_of_match);
+
+static struct platform_driver stm32_iwdg_driver = {
+ .probe = stm32_iwdg_probe,
+ .remove = stm32_iwdg_remove,
+ .driver = {
+ .name = "iwdg",
+ .of_match_table = stm32_iwdg_of_match,
+ },
+};
+module_platform_driver(stm32_iwdg_driver);
+
+MODULE_AUTHOR("Yannick Fertre <yannick.fertre@xxxxxx>");
+MODULE_DESCRIPTION("STMicroelectronics STM32 Independent Watchdog Driver");
+MODULE_LICENSE("GPL v2");