Message-ID: <b235ad1e-1f06-3ef6-b182-c8bea3055b4c@st.com>
Date:   Thu, 30 Mar 2017 15:10:34 +0000
From:   Yannick FERTRE <yannick.fertre@...com>
To:     Guenter Roeck <linux@...ck-us.net>,
        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-watchdog@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Philippe CORNU <philippe.cornu@...com>,
        Gabriel FERNANDEZ <gabriel.fernandez@...com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v3 2/5] drivers: watchdog: Add STM32 IWDG driver

Hi Guenter,
Many thanks for your help, I will push corrections to V4.

Best regards


On 03/29/2017 05:15 AM, Guenter Roeck wrote:
> 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>.
Ok done
>
>> +
>> +      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.
>
Ok, I remove the test.
>> +
>> +    /* 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 ?
>
Ok, done
>> +    }
>> +
>> +    /* 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.
Ok, I remove stop function
>
>> +    }
>> +
>> +    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() ?
Ok, done
>
>> +
>> +    /* 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.
>
Ok done
>> +
>> +    /* 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.
>
Ok, done
>> +    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.
Ok, removed
>
>> +    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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