Re: [PATCH v10 4/5] Watchdog: introduce ARM SBSA watchdog driver

[Mathieu Poirier]

On 3 February 2016 at 10:18,  <fu.wei@xxxxxxxxxx> wrote:
> From: Fu Wei <fu.wei@xxxxxxxxxx>
>
> According to Server Base System Architecture (SBSA) specification,
> the SBSA Generic Watchdog has two stage timeouts: the first signal (WS0)
> is for alerting the system by interrupt, the second one (WS1) is a real
> hardware reset.
>
> This patch initially implements a simple single stage watchdog driver:
> when the timeout is reached, your system will be reset by the second
> signal (WS1).
> The first signal (WS0) is ignored in this driver.
>
> This driver bases on linux kernel watchdog framework, so it can get
> timeout from module parameter and FDT at the driver init stage.
>
> Signed-off-by: Fu Wei <fu.wei@xxxxxxxxxx>
> Reviewed-by: Graeme Gregory <graeme.gregory@xxxxxxxxxx>
> Tested-by: Pratyush Anand <panand@xxxxxxxxxx>
> ---
>  drivers/watchdog/Kconfig     |  17 +++
>  drivers/watchdog/Makefile    |   1 +
>  drivers/watchdog/sbsa_gwdt.c | 322 +++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 340 insertions(+)
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 4f0e7be..4ab1b05 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -201,6 +201,23 @@ config ARM_SP805_WATCHDOG
>           ARM Primecell SP805 Watchdog timer. This will reboot your system when
>           the timeout is reached.
>
> +config ARM_SBSA_WATCHDOG
> +       tristate "ARM SBSA Generic Watchdog"
> +       depends on ARM64
> +       depends on ARM_ARCH_TIMER
> +       select WATCHDOG_CORE
> +       help
> +         ARM SBSA Generic Watchdog has two stage timeouts:
> +         the first signal (WS0) is for alerting the system by interrupt,
> +         the second one (WS1) is a real hardware reset.
> +         More details: ARM DEN0029B - Server Base System Architecture (SBSA)
> +
> +         This is a simple single stage driver: when the timeout is reached,
> +         your system will be reset by WS1. The first signal (WS0) is ignored.
> +
> +         To compile this driver as module, choose M here: The module
> +         will be called sbsa_gwdt.
> +
>  config ASM9260_WATCHDOG
>         tristate "Alphascale ASM9260 watchdog"
>         depends on MACH_ASM9260
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index f566753..f9826d4 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -30,6 +30,7 @@ obj-$(CONFIG_USBPCWATCHDOG) += pcwd_usb.o
>
>  # ARM Architecture
>  obj-$(CONFIG_ARM_SP805_WATCHDOG) += sp805_wdt.o
> +obj-$(CONFIG_ARM_SBSA_WATCHDOG) += sbsa_gwdt.o
>  obj-$(CONFIG_ASM9260_WATCHDOG) += asm9260_wdt.o
>  obj-$(CONFIG_AT91RM9200_WATCHDOG) += at91rm9200_wdt.o
>  obj-$(CONFIG_AT91SAM9X_WATCHDOG) += at91sam9_wdt.o
> diff --git a/drivers/watchdog/sbsa_gwdt.c b/drivers/watchdog/sbsa_gwdt.c
> new file mode 100644
> index 0000000..5a2dba3
> --- /dev/null
> +++ b/drivers/watchdog/sbsa_gwdt.c
> @@ -0,0 +1,322 @@
> +/*
> + * SBSA(Server Base System Architecture) Generic Watchdog driver
> + *
> + * Copyright (c) 2015, Linaro Ltd.
> + * Author: Fu Wei <fu.wei@xxxxxxxxxx>
> + *         Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>
> + *         Al Stone <al.stone@xxxxxxxxxx>
> + *         Timur Tabi <timur@xxxxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License 2 as published
> + * by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * This SBSA Generic watchdog driver is a single stage timeout version.
> + * Since this watchdog timer has two stages, and each stage is determined
> + * by WOR. So the timeout is (WOR * 2).
> + * When first timeout is reached, WS0 is triggered, the interrupt
> + * triggered by WS0 will be ignored, then the second watch period starts;
> + * when second timeout is reached, then WS1 is triggered, system reset.
> + *
> + * More details about the hardware specification of this device:
> + * ARM DEN0029B - Server Base System Architecture (SBSA)
> + *
> + * SBSA GWDT: |--------WOR-------WS0--------WOR-------WS1
> + *            |----------------timeout----------------reset
> + *
> + */
> +
> +#include <linux/io.h>
> +#include <linux/interrupt.h>
> +#include <linux/module.h>
> +#include <linux/moduleparam.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/uaccess.h>
> +#include <linux/watchdog.h>
> +#include <asm/arch_timer.h>
> +
> +/* SBSA Generic Watchdog register definitions */
> +/* refresh frame */
> +#define SBSA_GWDT_WRR                          0x000
> +
> +/* control frame */
> +#define SBSA_GWDT_WCS                          0x000
> +#define SBSA_GWDT_WOR                          0x008
> +#define SBSA_GWDT_WCV                          0x010
> +
> +/* refresh/control frame */
> +#define SBSA_GWDT_W_IIDR                       0xfcc
> +#define SBSA_GWDT_IDR                          0xfd0
> +
> +/* Watchdog Control and Status Register */
> +#define SBSA_GWDT_WCS_EN                       BIT(0)
> +#define SBSA_GWDT_WCS_WS0                      BIT(1)
> +#define SBSA_GWDT_WCS_WS1                      BIT(2)
> +
> +/**
> + * struct sbsa_gwdt - Internal representation of the SBSA GWDT
> + * @wdd:               kernel watchdog_device structure
> + * @clk:               store the System Counter clock frequency, in Hz.
> + * @refresh_base:      Virtual address of the watchdog refresh frame
> + * @control_base:      Virtual address of the watchdog control frame
> + */
> +struct sbsa_gwdt {
> +       struct watchdog_device  wdd;
> +       u32                     clk;
> +       void __iomem            *refresh_base;
> +       void __iomem            *control_base;
> +};
> +
> +#define to_sbsa_gwdt(e) container_of(e, struct sbsa_gwdt, wdd)
> +
> +#define DEFAULT_TIMEOUT                20 /* seconds, the 1st + 2nd watch periods*/
> +
> +static unsigned int timeout;
> +module_param(timeout, uint, 0);
> +MODULE_PARM_DESC(timeout,
> +                "Watchdog timeout in seconds. (>=0, default="
> +                __MODULE_STRING(DEFAULT_TIMEOUT) ")");
> +
> +static bool nowayout = WATCHDOG_NOWAYOUT;
> +module_param(nowayout, bool, S_IRUGO);
> +MODULE_PARM_DESC(nowayout,
> +                "Watchdog cannot be stopped once started (default="
> +                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
> +
> +/*
> + * watchdog operation functions
> + */
> +static int sbsa_gwdt_set_timeout(struct watchdog_device *wdd,
> +                                unsigned int timeout)
> +{
> +       struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +       wdd->timeout = timeout;
> +       writel(timeout / 2 * gwdt->clk, gwdt->control_base + SBSA_GWDT_WOR);
> +
> +       return 0;
> +}
> +
> +static unsigned int sbsa_gwdt_get_timeleft(struct watchdog_device *wdd)
> +{
> +       struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +       u64 timeleft = readq(gwdt->control_base + SBSA_GWDT_WCV) -
> +                      arch_counter_get_cntvct();
> +
> +       do_div(timeleft, gwdt->clk);
> +
> +       if (readl(gwdt->control_base + SBSA_GWDT_WCS) & SBSA_GWDT_WCS_WS0)
> +               return timeleft;
> +
> +       return timeleft + wdd->timeout / 2;

It would be great to have a comment whenever hard coded values are
used.  That way people understand why things were set this way.  The
same applies for the rest of this patch.

> +}
> +
> +static int sbsa_gwdt_keepalive(struct watchdog_device *wdd)
> +{
> +       struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +       /*
> +       * Writing WRR for an explicit watchdog refresh.
> +       * You can write anyting(like 0xc0ffee).
> +       */
> +       writel(0xc0ffee, gwdt->refresh_base + SBSA_GWDT_WRR);
> +
> +       return 0;
> +}
> +
> +static unsigned int sbsa_gwdt_status(struct watchdog_device *wdd)
> +{
> +       struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +       u32 status = readl(gwdt->control_base + SBSA_GWDT_WCS);
> +
> +       /* is the watchdog timer running? */
> +       return (status & SBSA_GWDT_WCS_EN) << WDOG_ACTIVE;
> +}
> +
> +static int sbsa_gwdt_start(struct watchdog_device *wdd)
> +{
> +       struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +       /* writing WCS will cause an explicit watchdog refresh */
> +       writel(SBSA_GWDT_WCS_EN, gwdt->control_base + SBSA_GWDT_WCS);
> +
> +       return sbsa_gwdt_keepalive(wdd);
> +}
> +
> +static int sbsa_gwdt_stop(struct watchdog_device *wdd)
> +{
> +       struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd);
> +
> +       writel(0, gwdt->control_base + SBSA_GWDT_WCS);
> +
> +       return 0;
> +}
> +
> +static struct watchdog_info sbsa_gwdt_info = {
> +       .identity       = "SBSA Generic Watchdog",
> +       .options        = WDIOF_SETTIMEOUT |
> +                         WDIOF_KEEPALIVEPING |
> +                         WDIOF_MAGICCLOSE |
> +                         WDIOF_CARDRESET,
> +};
> +
> +static struct watchdog_ops sbsa_gwdt_ops = {
> +       .owner          = THIS_MODULE,
> +       .start          = sbsa_gwdt_start,
> +       .stop           = sbsa_gwdt_stop,
> +       .status         = sbsa_gwdt_status,
> +       .ping           = sbsa_gwdt_keepalive,
> +       .set_timeout    = sbsa_gwdt_set_timeout,
> +       .get_timeleft   = sbsa_gwdt_get_timeleft,
> +};
> +
> +static int sbsa_gwdt_probe(struct platform_device *pdev)
> +{
> +       void __iomem *rf_base, *cf_base;
> +       struct device *dev = &pdev->dev;
> +       struct watchdog_device *wdd;
> +       struct sbsa_gwdt *gwdt;
> +       struct resource *res;
> +       u32 status;
> +       int ret;
> +
> +       gwdt = devm_kzalloc(dev, sizeof(*gwdt), GFP_KERNEL);
> +       if (!gwdt)
> +               return -ENOMEM;
> +       platform_set_drvdata(pdev, gwdt);
> +
> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       cf_base = devm_ioremap_resource(dev, res);
> +       if (IS_ERR(cf_base))
> +               return PTR_ERR(cf_base);
> +
> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 1);
> +       rf_base = devm_ioremap_resource(dev, res);
> +       if (IS_ERR(rf_base))
> +               return PTR_ERR(rf_base);
> +
> +       /*
> +        * Get the frequency of system counter from the cp15 interface of ARM
> +        * Generic timer. We don't need to check it, because if it returns "0",
> +        * system would panic in very early stage.
> +        */
> +       gwdt->clk = arch_timer_get_cntfrq();
> +       gwdt->refresh_base = rf_base;
> +       gwdt->control_base = cf_base;
> +
> +       wdd = &gwdt->wdd;
> +       wdd->parent = dev;
> +       wdd->info = &sbsa_gwdt_info;
> +       wdd->ops = &sbsa_gwdt_ops;
> +       watchdog_set_drvdata(wdd, gwdt);
> +       watchdog_set_nowayout(wdd, nowayout);
> +
> +       wdd->min_timeout = 2;
> +       wdd->max_timeout = U32_MAX / gwdt->clk * 2;
> +       wdd->timeout = DEFAULT_TIMEOUT;
> +       watchdog_init_timeout(wdd, timeout, dev);
> +
> +       status = readl(gwdt->control_base + SBSA_GWDT_WCS);
> +       if (status & SBSA_GWDT_WCS_WS1) {
> +               dev_warn(dev, "System reset by WDT.\n");
> +               wdd->bootstatus |= WDIOF_CARDRESET;
> +       }
> +
> +       ret = watchdog_register_device(wdd);
> +       if (ret)
> +               return ret;
> +
> +       /*
> +        * Update timeout to WOR.
> +        * Because of the explicit watchdog refresh mechanism,
> +        * it's also a ping, if watchdog is enabled.
> +        */
> +       sbsa_gwdt_set_timeout(wdd, wdd->timeout);
> +
> +       dev_info(dev, "Initialized with %ds timeout @ %u Hz%s\n", wdd->timeout,
> +                gwdt->clk, status & SBSA_GWDT_WCS_EN ? " [enabled]" : "");
> +
> +       return 0;
> +}
> +
> +static void sbsa_gwdt_shutdown(struct platform_device *pdev)
> +{
> +       struct sbsa_gwdt *gwdt = platform_get_drvdata(pdev);
> +
> +       sbsa_gwdt_stop(&gwdt->wdd);
> +}
> +
> +static int sbsa_gwdt_remove(struct platform_device *pdev)
> +{
> +       struct sbsa_gwdt *gwdt = platform_get_drvdata(pdev);
> +
> +       watchdog_unregister_device(&gwdt->wdd);
> +
> +       return 0;
> +}
> +
> +/* Disable watchdog if it is active during suspend */
> +static int __maybe_unused sbsa_gwdt_suspend(struct device *dev)
> +{
> +       struct sbsa_gwdt *gwdt = dev_get_drvdata(dev);
> +
> +       if (watchdog_active(&gwdt->wdd))
> +               sbsa_gwdt_stop(&gwdt->wdd);
> +
> +       return 0;
> +}
> +
> +/* Enable watchdog and configure it if necessary */
> +static int __maybe_unused sbsa_gwdt_resume(struct device *dev)
> +{
> +       struct sbsa_gwdt *gwdt = dev_get_drvdata(dev);
> +
> +       if (watchdog_active(&gwdt->wdd))
> +               sbsa_gwdt_start(&gwdt->wdd);
> +
> +       return 0;
> +}
> +
> +static const struct dev_pm_ops sbsa_gwdt_pm_ops = {
> +       SET_SYSTEM_SLEEP_PM_OPS(sbsa_gwdt_suspend, sbsa_gwdt_resume)
> +};
> +
> +static const struct of_device_id sbsa_gwdt_of_match[] = {
> +       { .compatible = "arm,sbsa-gwdt", },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, sbsa_gwdt_of_match);
> +
> +static const struct platform_device_id sbsa_gwdt_pdev_match[] = {
> +       { .name = "sbsa-gwdt", },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(platform, sbsa_gwdt_pdev_match);
> +
> +static struct platform_driver sbsa_gwdt_driver = {
> +       .driver = {
> +               .name = "sbsa-gwdt",
> +               .pm = &sbsa_gwdt_pm_ops,
> +               .of_match_table = sbsa_gwdt_of_match,
> +       },
> +       .probe = sbsa_gwdt_probe,
> +       .remove = sbsa_gwdt_remove,
> +       .shutdown = sbsa_gwdt_shutdown,
> +       .id_table = sbsa_gwdt_pdev_match,
> +};
> +
> +module_platform_driver(sbsa_gwdt_driver);
> +
> +MODULE_DESCRIPTION("SBSA Generic Watchdog Driver");
> +MODULE_AUTHOR("Fu Wei <fu.wei@xxxxxxxxxx>");
> +MODULE_AUTHOR("Suravee Suthikulpanit <Suravee.Suthikulpanit@xxxxxxx>");
> +MODULE_AUTHOR("Al Stone <al.stone@xxxxxxxxxx>");
> +MODULE_AUTHOR("Timur Tabi <timur@xxxxxxxxxxxxxx>");
> +MODULE_LICENSE("GPL v2");
> --
> 2.5.0
>