Re: [PATCH v3 2/2] watchdog: Add Realtek Otto watchdog timer

Guenter Roeck
2021-11-17T05:21:00Z

On Thu, Nov 04, 2021 at 10:32:13AM +0100, Sander Vanheule wrote:
> Realtek MIPS SoCs (platform name Otto) have a watchdog timer with
> pretimeout notifitication support. The WDT can (partially) hard reset,
> or soft reset the SoC.
>
> This driver implements all features as described in the devicetree
> binding, except the phase2 interrupt, and also functions as a restart
> handler. The cpu reset mode is considered to be a "warm" restart, since
> this mode does not reset all peripherals. Being an embedded system
> though, the "cpu" and "software" modes will still cause the bootloader
> to run on restart.
>
> It is not known how a forced system reset can be disabled on the
> supported platforms. This means that the phase2 interrupt will only fire
> at the same time as reset, so implementing phase2 is of little use.
>
> Signed-off-by: Sander Vanheule <sander@svanheule.net>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

>
> --

Note for the future: Change log should be after '---'.

> v2 -> v3:
> - fix off-by-one error in PRESCALE assignment
>
> v1 -> v2:
> - drop raw_spinlock, locking is not required
> - replace devm_free_irq with disable_irq
> - use max_hw_heartbeat_ms instead of max_timeout
> - drop redundant timeout value checks
> - replace ROUND_CLOSEST by ROUND_UP for tick counts, and flooring
> division for timeout values
> - change COMMON_CLK 'select' into 'depends on'
> - add MODULE_DEVICE_TABLE for OF ID table
> - add realtek,rtl9300 compatible
> - drop phase2 irq
> ---
> MAINTAINERS | 7 +
> drivers/watchdog/Kconfig | 13 +
> drivers/watchdog/Makefile | 1 +
> drivers/watchdog/realtek_otto_wdt.c | 361 ++++++++++++++++++++++++++++
> 4 files changed, 382 insertions(+)
> create mode 100644 drivers/watchdog/realtek_otto_wdt.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2c9070aeba2a..54c8f788d3e5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15991,6 +15991,13 @@ S: Maintained
> F: include/sound/rt*.h
> F: sound/soc/codecs/rt*
>
> +REALTEK OTTO WATCHDOG
> +M: Sander Vanheule <sander@svanheule.net>
> +L: linux-watchdog@vger.kernel.org
> +S: Maintained
> +F: Documentation/devicetree/bindings/watchdog/realtek,otto-wdt.yaml
> +F: driver/watchdog/realtek_otto_wdt.c
> +
> REALTEK RTL83xx SMI DSA ROUTER CHIPS
> M: Linus Walleij <linus.walleij@linaro.org>
> S: Maintained
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index bf59faeb3de1..d308e13a9aa1 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -954,6 +954,19 @@ config RTD119X_WATCHDOG
> Say Y here to include support for the watchdog timer in
> Realtek RTD1295 SoCs.
>
> +config REALTEK_OTTO_WDT
> + tristate "Realtek Otto MIPS watchdog support"
> + depends on MACH_REALTEK_RTL || COMPILE_TEST
> + depends on COMMON_CLK
> + select WATCHDOG_CORE
> + default MACH_REALTEK_RTL
> + help
> + Say Y here to include support for the watchdog timer on Realtek
> + RTL838x, RTL839x, RTL930x SoCs. This watchdog has pretimeout
> + notifications and system reset on timeout.
> +
> + When built as a module this will be called realtek_otto_wdt.
> +
> config SPRD_WATCHDOG
> tristate "Spreadtrum watchdog support"
> depends on ARCH_SPRD || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index 1bd2d6f37c53..a8dccf819163 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -171,6 +171,7 @@ obj-$(CONFIG_IMGPDC_WDT) += imgpdc_wdt.o
> obj-$(CONFIG_MT7621_WDT) += mt7621_wdt.o
> obj-$(CONFIG_PIC32_WDT) += pic32-wdt.o
> obj-$(CONFIG_PIC32_DMT) += pic32-dmt.o
> +obj-$(CONFIG_REALTEK_OTTO_WDT) += realtek_otto_wdt.o
>
> # PARISC Architecture
>
> diff --git a/drivers/watchdog/realtek_otto_wdt.c b/drivers/watchdog/realtek_otto_wdt.c
> new file mode 100644
> index 000000000000..48bc8dfefc25
> --- /dev/null
> +++ b/drivers/watchdog/realtek_otto_wdt.c
> @@ -0,0 +1,361 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +/*
> + * Realtek Otto MIPS platform watchdog
> + *
> + * Watchdog timer that will reset the system after timeout, using the selected
> + * reset mode.
> + *
> + * Counter scaling and timeouts:
> + * - Base prescale of (2 << 25), providing tick duration T_0: 168ms @ 200MHz
> + * - PRESCALE: logarithmic prescaler adding a factor of {1, 2, 4, 8}
> + * - Phase 1: Times out after (PHASE1 + 1) × PRESCALE × T_0
> + * Generates an interrupt, WDT cannot be stopped after phase 1
> + * - Phase 2: starts after phase 1, times out after (PHASE2 + 1) × PRESCALE × T_0
> + * Resets the system according to RST_MODE
> + */
> +
> +#include <linux/bits.h>
> +#include <linux/bitfield.h>
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/math.h>
> +#include <linux/minmax.h>
> +#include <linux/module.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/platform_device.h>
> +#include <linux/property.h>
> +#include <linux/reboot.h>
> +#include <linux/watchdog.h>
> +
> +#define OTTO_WDT_REG_CNTR 0x0
> +#define OTTO_WDT_CNTR_PING BIT(31)
> +
> +#define OTTO_WDT_REG_INTR 0x4
> +#define OTTO_WDT_INTR_PHASE_1 BIT(31)
> +#define OTTO_WDT_INTR_PHASE_2 BIT(30)
> +
> +#define OTTO_WDT_REG_CTRL 0x8
> +#define OTTO_WDT_CTRL_ENABLE BIT(31)
> +#define OTTO_WDT_CTRL_PRESCALE GENMASK(30, 29)
> +#define OTTO_WDT_CTRL_PHASE1 GENMASK(26, 22)
> +#define OTTO_WDT_CTRL_PHASE2 GENMASK(19, 15)
> +#define OTTO_WDT_CTRL_RST_MODE GENMASK(1, 0)
> +#define OTTO_WDT_MODE_SOC 0
> +#define OTTO_WDT_MODE_CPU 1
> +#define OTTO_WDT_MODE_SOFTWARE 2
> +#define OTTO_WDT_CTRL_DEFAULT OTTO_WDT_MODE_CPU
> +
> +#define OTTO_WDT_PRESCALE_MAX 3
> +
> +/*
> + * One higher than the max values contained in PHASE{1,2}, since a value of 0
> + * corresponds to one tick.
> + */
> +#define OTTO_WDT_PHASE_TICKS_MAX 32
> +
> +/*
> + * The maximum reset delay is actually 2×32 ticks, but that would require large
> + * pretimeout values for timeouts longer than 32 ticks. Limit the maximum timeout
> + * to 32 + 1 to ensure small pretimeout values can be configured as expected.
> + */
> +#define OTTO_WDT_TIMEOUT_TICKS_MAX (OTTO_WDT_PHASE_TICKS_MAX + 1)
> +
> +struct otto_wdt_ctrl {
> + struct watchdog_device wdev;
> + struct device *dev;
> + void __iomem *base;
> + struct clk *clk;
> + int irq_phase1;
> +};
> +
> +static int otto_wdt_start(struct watchdog_device *wdev)
> +{
> + struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
> + u32 v;
> +
> + v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
> + v |= OTTO_WDT_CTRL_ENABLE;
> + iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + return 0;
> +}
> +
> +static int otto_wdt_stop(struct watchdog_device *wdev)
> +{
> + struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
> + u32 v;
> +
> + v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
> + v &= ~OTTO_WDT_CTRL_ENABLE;
> + iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + return 0;
> +}
> +
> +static int otto_wdt_ping(struct watchdog_device *wdev)
> +{
> + struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
> +
> + iowrite32(OTTO_WDT_CNTR_PING, ctrl->base + OTTO_WDT_REG_CNTR);
> +
> + return 0;
> +}
> +
> +static int otto_wdt_tick_ms(struct otto_wdt_ctrl *ctrl, int prescale)
> +{
> + unsigned int rate_khz = clk_get_rate(ctrl->clk) / 1000;
> +
> + if (!rate_khz)
> + return 0;
> +
> + return DIV_ROUND_CLOSEST(1 << (25 + prescale), rate_khz);
> +}
> +
> +/*
> + * The timer asserts the PHASE1/PHASE2 IRQs when the number of ticks exceeds
> + * the value stored in those fields. This means each phase will run for at least
> + * one tick, so small values need to be clamped to correctly reflect the timeout.
> + */
> +static inline unsigned int div_round_ticks(unsigned int val, unsigned int tick_duration,
> + unsigned int min_ticks)
> +{
> + return max(min_ticks, DIV_ROUND_UP(val, tick_duration));
> +}
> +
> +static int otto_wdt_determine_timeouts(struct watchdog_device *wdev, unsigned int timeout,
> + unsigned int pretimeout)
> +{
> + struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
> + unsigned int pretimeout_ms = pretimeout * 1000;
> + unsigned int timeout_ms = timeout * 1000;
> + unsigned int prescale_next = 0;
> + unsigned int phase1_ticks;
> + unsigned int phase2_ticks;
> + unsigned int total_ticks;
> + unsigned int prescale;
> + unsigned int tick_ms;
> + u32 v;
> +
> + do {
> + prescale = prescale_next;
> + if (prescale > OTTO_WDT_PRESCALE_MAX)
> + return -EINVAL;
> +
> + tick_ms = otto_wdt_tick_ms(ctrl, prescale);
> + total_ticks = div_round_ticks(timeout_ms, tick_ms, 2);
> + phase1_ticks = div_round_ticks(timeout_ms - pretimeout_ms, tick_ms, 1);
> + phase2_ticks = total_ticks - phase1_ticks;
> +
> + prescale_next++;
> + } while (phase1_ticks > OTTO_WDT_PHASE_TICKS_MAX
> + || phase2_ticks > OTTO_WDT_PHASE_TICKS_MAX);
> +
> + v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + v &= ~(OTTO_WDT_CTRL_PRESCALE | OTTO_WDT_CTRL_PHASE1 | OTTO_WDT_CTRL_PHASE2);
> + v |= FIELD_PREP(OTTO_WDT_CTRL_PHASE1, phase1_ticks - 1);
> + v |= FIELD_PREP(OTTO_WDT_CTRL_PHASE2, phase2_ticks - 1);
> + v |= FIELD_PREP(OTTO_WDT_CTRL_PRESCALE, prescale);
> +
> + iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + timeout_ms = total_ticks * tick_ms;
> + ctrl->wdev.timeout = timeout_ms / 1000;
> +
> + pretimeout_ms = phase2_ticks * tick_ms;
> + ctrl->wdev.pretimeout = pretimeout_ms / 1000;
> +
> + return 0;
> +}
> +
> +static int otto_wdt_set_timeout(struct watchdog_device *wdev, unsigned int val)
> +{
> + return otto_wdt_determine_timeouts(wdev, val, min(wdev->pretimeout, val - 1));
> +}
> +
> +static int otto_wdt_set_pretimeout(struct watchdog_device *wdev, unsigned int val)
> +{
> + return otto_wdt_determine_timeouts(wdev, wdev->timeout, val);
> +}
> +
> +static int otto_wdt_restart(struct watchdog_device *wdev, unsigned long reboot_mode,
> + void *data)
> +{
> + struct otto_wdt_ctrl *ctrl = watchdog_get_drvdata(wdev);
> + u32 reset_mode;
> + u32 v;
> +
> + disable_irq(ctrl->irq_phase1);
> +
> + switch (reboot_mode) {
> + case REBOOT_SOFT:
> + reset_mode = OTTO_WDT_MODE_SOFTWARE;
> + break;
> + case REBOOT_WARM:
> + reset_mode = OTTO_WDT_MODE_CPU;
> + break;
> + default:
> + reset_mode = OTTO_WDT_MODE_SOC;
> + break;
> + }
> +
> + /* Configure for shortest timeout and wait for reset to occur */
> + v = FIELD_PREP(OTTO_WDT_CTRL_RST_MODE, reset_mode) | OTTO_WDT_CTRL_ENABLE;
> + iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + mdelay(3 * otto_wdt_tick_ms(ctrl, 0));
> +
> + return 0;
> +}
> +
> +static irqreturn_t otto_wdt_phase1_isr(int irq, void *dev_id)
> +{
> + struct otto_wdt_ctrl *ctrl = dev_id;
> +
> + iowrite32(OTTO_WDT_INTR_PHASE_1, ctrl->base + OTTO_WDT_REG_INTR);
> + dev_crit(ctrl->dev, "phase 1 timeout\n");
> + watchdog_notify_pretimeout(&ctrl->wdev);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static const struct watchdog_ops otto_wdt_ops = {
> + .owner = THIS_MODULE,
> + .start = otto_wdt_start,
> + .stop = otto_wdt_stop,
> + .ping = otto_wdt_ping,
> + .set_timeout = otto_wdt_set_timeout,
> + .set_pretimeout = otto_wdt_set_pretimeout,
> + .restart = otto_wdt_restart,
> +};
> +
> +static const struct watchdog_info otto_wdt_info = {
> + .identity = "Realtek Otto watchdog timer",
> + .options = WDIOF_KEEPALIVEPING |
> + WDIOF_MAGICCLOSE |
> + WDIOF_SETTIMEOUT |
> + WDIOF_PRETIMEOUT,
> +};
> +
> +static int otto_wdt_probe_reset_mode(struct otto_wdt_ctrl *ctrl)
> +{
> + static const char *mode_property = "realtek,reset-mode";
> + const struct fwnode_handle *node = ctrl->dev->fwnode;
> + int mode_count;
> + u32 mode;
> + u32 v;
> +
> + if (!node)
> + return -ENXIO;
> +
> + mode_count = fwnode_property_string_array_count(node, mode_property);
> + if (mode_count < 0)
> + return mode_count;
> + else if (mode_count == 0)
> + return 0;
> + else if (mode_count != 1)
> + return -EINVAL;
> +
> + if (fwnode_property_match_string(node, mode_property, "soc") == 0)
> + mode = OTTO_WDT_MODE_SOC;
> + else if (fwnode_property_match_string(node, mode_property, "cpu") == 0)
> + mode = OTTO_WDT_MODE_CPU;
> + else if (fwnode_property_match_string(node, mode_property, "software") == 0)
> + mode = OTTO_WDT_MODE_SOFTWARE;
> + else
> + return -EINVAL;
> +
> + v = ioread32(ctrl->base + OTTO_WDT_REG_CTRL);
> + v &= ~OTTO_WDT_CTRL_RST_MODE;
> + v |= FIELD_PREP(OTTO_WDT_CTRL_RST_MODE, mode);
> + iowrite32(v, ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + return 0;
> +}
> +
> +static int otto_wdt_probe(struct platform_device *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct otto_wdt_ctrl *ctrl;
> + unsigned int max_tick_ms;
> + int ret;
> +
> + ctrl = devm_kzalloc(dev, sizeof(*ctrl), GFP_KERNEL);
> + if (!ctrl)
> + return -ENOMEM;
> +
> + ctrl->dev = dev;
> + ctrl->base = devm_platform_ioremap_resource(pdev, 0);
> + if (IS_ERR(ctrl->base))
> + return PTR_ERR(ctrl->base);
> +
> + /* Clear any old interrupts and reset initial state */
> + iowrite32(OTTO_WDT_INTR_PHASE_1 | OTTO_WDT_INTR_PHASE_2,
> + ctrl->base + OTTO_WDT_REG_INTR);
> + iowrite32(OTTO_WDT_CTRL_DEFAULT, ctrl->base + OTTO_WDT_REG_CTRL);
> +
> + ctrl->clk = devm_clk_get(dev, NULL);
> + if (IS_ERR(ctrl->clk))
> + return dev_err_probe(dev, PTR_ERR(ctrl->clk), "Failed to get clock\n");
> +
> + ctrl->irq_phase1 = platform_get_irq_byname(pdev, "phase1");
> + if (ctrl->irq_phase1 < 0)
> + return dev_err_probe(dev, ctrl->irq_phase1, "phase1 IRQ not found\n");
> +
> + ret = devm_request_irq(dev, ctrl->irq_phase1, otto_wdt_phase1_isr, 0,
> + "realtek-otto-wdt", ctrl);
> + if (ret)
> + return dev_err_probe(dev, ret, "Failed to get IRQ for phase1\n");
> +
> + ret = otto_wdt_probe_reset_mode(ctrl);
> + if (ret)
> + return dev_err_probe(dev, ret, "Invalid reset mode specified\n");
> +
> + ctrl->wdev.parent = dev;
> + ctrl->wdev.info = &otto_wdt_info;
> + ctrl->wdev.ops = &otto_wdt_ops;
> +
> + /*
> + * Since pretimeout cannot be disabled, min. timeout is twice the
> + * subsystem resolution. max. timeout is ca. 43s at a bus clock of 200MHz.
> + */
> + ctrl->wdev.min_timeout = 2;
> + max_tick_ms = otto_wdt_tick_ms(ctrl, OTTO_WDT_PRESCALE_MAX);
> + ctrl->wdev.max_hw_heartbeat_ms = max_tick_ms * OTTO_WDT_TIMEOUT_TICKS_MAX;
> + ctrl->wdev.timeout = min(30U, ctrl->wdev.max_hw_heartbeat_ms / 1000);
> +
> + watchdog_set_drvdata(&ctrl->wdev, ctrl);
> + watchdog_init_timeout(&ctrl->wdev, 0, dev);
> + watchdog_stop_on_reboot(&ctrl->wdev);
> + watchdog_set_restart_priority(&ctrl->wdev, 128);
> +
> + ret = otto_wdt_determine_timeouts(&ctrl->wdev, ctrl->wdev.timeout, 1);
> + if (ret)
> + return dev_err_probe(dev, ret, "Failed to set timeout\n");
> +
> + return devm_watchdog_register_device(dev, &ctrl->wdev);
> +}
> +
> +static const struct of_device_id otto_wdt_ids[] = {
> + { .compatible = "realtek,rtl8380-wdt" },
> + { .compatible = "realtek,rtl8390-wdt" },
> + { .compatible = "realtek,rtl9300-wdt" },
> + { }
> +};
> +MODULE_DEVICE_TABLE(of, otto_wdt_ids);
> +
> +static struct platform_driver otto_wdt_driver = {
> + .probe = otto_wdt_probe,
> + .driver = {
> + .name = "realtek-otto-watchdog",
> + .of_match_table = otto_wdt_ids,
> + },
> +};
> +module_platform_driver(otto_wdt_driver);
> +
> +MODULE_LICENSE("GPL v2");
> +MODULE_AUTHOR("Sander Vanheule <sander@svanheule.net>");
> +MODULE_DESCRIPTION("Realtek Otto watchdog timer driver");
> --
> 2.31.1
>