Re: [PATCH v2 5/6] watchdog: Add Renesas RZ/N1 Watchdog driver

[Geert Uytterhoeven]

Hi Jean-Jacques,

On Tue, Feb 8, 2022 at 7:35 PM Jean-Jacques Hiblot
<jjhiblot@xxxxxxxxxxxxxxx> wrote:
> From: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
>
> This is a driver for the standard WDT on the RZ/N1 devices. This WDT has
> very limited timeout capabilities. However, it can reset the device.
> To do so, the corresponding bits in the SysCtrl RSTEN register need to
> be enabled. This is not done by this driver.
>
> Signed-off-by: Phil Edworthy <phil.edworthy@xxxxxxxxxxx>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@xxxxxxxxxxxxxxx>

Thanks for your patch!

> --- /dev/null
> +++ b/drivers/watchdog/rzn1_wdt.c
> @@ -0,0 +1,208 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Renesas RZ/N1 Watchdog timer.
> + * This is a 12-bit timer driver from a (62.5/16384) MHz clock. It can't even
> + * cope with 2 seconds.
> + *
> + * Copyright 2018 Renesas Electronics Europe Ltd.
> + *
> + * Derived from Ralink RT288x watchdog timer.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/watchdog.h>
> +
> +#define DEFAULT_TIMEOUT                60
> +
> +#define RZN1_WDT_RETRIGGER                     0x0
> +#define RZN1_WDT_RETRIGGER_RELOAD_VAL          0
> +#define RZN1_WDT_RETRIGGER_RELOAD_VAL_MASK     0xfff
> +#define RZN1_WDT_RETRIGGER_PRESCALE            BIT(12)
> +#define RZN1_WDT_RETRIGGER_ENABLE              BIT(13)
> +#define RZN1_WDT_RETRIGGER_WDSI                        (0x2 << 14)
> +
> +#define RZN1_WDT_PRESCALER                     16384
> +#define RZN1_WDT_MAX                           4095
> +
> +struct rzn1_watchdog {
> +       struct watchdog_device          wdt;
> +       void __iomem                    *base;
> +       unsigned long                   clk_rate;
> +};
> +
> +#define to_rzn1_watchdog(_ptr) \
> +       container_of(_ptr, struct rzn1_watchdog, wdt)
> +
> +static inline uint32_t get_max_heart_beat(uint32_t clk_rate)

unsigned long clk_rate

> +{
> +       return (RZN1_WDT_MAX * RZN1_WDT_PRESCALER) / (clk_rate / 1000);

Is clk_rate always a multiple of 1000? If not, you want to reorder
this to avoid losing precision.

> +}
> +static inline uint32_t compute_reload_value(uint32_t tick_ms, uint32_t clk)

unsigned long clk_rate

> +{
> +       return (tick_ms * (clk / 1000)) / RZN1_WDT_PRESCALER;

Likewise.

> +}

> +static int rzn1_wdt_probe(struct platform_device *pdev)
> +{
> +       struct device *dev = &pdev->dev;
> +       struct rzn1_watchdog *wdt;
> +       struct device_node *np = dev->of_node;
> +       struct clk *clk;
> +       int ret;
> +       int irq;
> +
> +       wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> +       if (!wdt)
> +               return -ENOMEM;
> +
> +       wdt->wdt = rzn1_wdt;
> +       wdt->wdt.parent = dev;
> +
> +       wdt->base = devm_platform_ioremap_resource(pdev, 0);
> +       if (IS_ERR(wdt->base))
> +               return PTR_ERR(wdt->base);
> +
> +       irq = platform_get_irq(pdev, 0);
> +       if (irq < 0) {
> +               dev_err(dev, "failed to get the irq\n");

No need to print a message, platform_get_irq() already does that.

> +               return irq;
> +       }
> +
> +       ret = devm_request_irq(dev, irq, rzn1_wdt_irq, 0,
> +                              np->name, wdt);
> +       if (ret) {
> +               dev_err(dev, "failed to request irq %d\n", irq);
> +               return ret;
> +       }
> +
> +       clk = devm_clk_get(dev, NULL);
> +       if (IS_ERR(clk)) {
> +               dev_err(dev, "failed to get the clock\n");
> +               return PTR_ERR(clk);
> +       }
> +
> +       ret = clk_prepare_enable(clk);
> +       if (ret) {
> +               dev_err(dev, "failed to prepare/enable the clock\n");
> +               return ret;
> +       }
> +
> +       ret = devm_add_action_or_reset(dev, rzn1_wdt_clk_disable_unprepare,
> +                                      clk);
> +       if (ret) {
> +               dev_err(dev, "failed to register clock unprepare callback\n");
> +               clk_disable_unprepare(clk);

Please drop this, as devm_add_action_or_reset() calls the
action on failure.

> +               return ret;
> +       }
> +
> +       wdt->clk_rate = clk_get_rate(clk);
> +       if (!wdt->clk_rate) {
> +               dev_err(dev, "failed to get the clock rate\n");
> +               return -EINVAL;
> +       }
> +
> +       /*
> +        * The period of the watchdog cannot be changed once set
> +        * and is limited to a very short period.
> +        * Configure it for a 1s period once and for all, and
> +        * rely on the heart-beat provided by the watchdog core
> +        * to make this usable by the user-space.
> +        */
> +       wdt->wdt.max_hw_heartbeat_ms = get_max_heart_beat(wdt->clk_rate);
> +       if (wdt->wdt.max_hw_heartbeat_ms > 1000)
> +               wdt->wdt.max_hw_heartbeat_ms = 1000;
> +
> +       wdt->wdt.timeout = DEFAULT_TIMEOUT;
> +       ret = watchdog_init_timeout(&wdt->wdt, 0, dev);
> +
> +       return devm_watchdog_register_device(dev, &wdt->wdt);
> +}
> +
> +
> +static const struct of_device_id rzn1_wdt_match[] = {
> +       { .compatible = "renesas,r9a06g032-wdt" },

No need to match on the soc-specific compatible value, as the
family-specific value should be present in the DTB, too.

> +       { .compatible = "renesas,rzn1-wdt" },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, rzn1_wdt_match);

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds