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Message-ID: <ac425e69-2d3c-2257-7183-115fbe9eb2b0@roeck-us.net>
Date: Tue, 28 Mar 2017 20:15:15 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Yannick Fertre <yannick.fertre@...com>,
Wim Van Sebroeck <wim@...ana.be>,
Rob Herring <robh+dt@...nel.org>,
Alexandre TORGUE <alexandre.torgue@...com>,
Benjamin Gaignard <benjamin.gaignard@...com>,
Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc: linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org,
Philippe Cornu <philippe.cornu@...com>,
Gabriel FERNANDEZ <gabriel.fernandez@...com>,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/5] drivers: watchdog: Add STM32 IWDG driver
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@...com>
> ---
> 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@...com>
> + *
> + * 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@...com>");
> +MODULE_DESCRIPTION("STMicroelectronics STM32 Independent Watchdog Driver");
> +MODULE_LICENSE("GPL v2");
>
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