Re: [PATCH v6] watchdog: orion_wdt: use timer1 as a pretimeout

[Guenter Roeck <linux@roeck-us.net>]

On Fri, Aug 30, 2019 at 09:52:24AM +1200, Chris Packham wrote:
> The orion watchdog can either reset the CPU or generate an interrupt.
> The interrupt would be useful for debugging as it provides panic()
> output about the watchdog expiry, however if the interrupt is used the
> watchdog can't reset the CPU in the event of being stuck in a loop with
> interrupts disabled or if the CPU is prevented from accessing memory
> (e.g. an unterminated DMA).
> 
> The Armada SoCs have spare timers that aren't currently used by the
> Linux kernel. We can use timer1 to provide a pre-timeout ahead of the
> watchdog timer and provide the possibility of gathering debug before the
> reset triggers.
> 
> Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>

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

> ---
> Changes in v6:
> - Fix bitwise operation in armada375_stop()
> - Add comment about 2nd interrupt being optional
> Changes in v5:
> - Group bit values with register addresses
> - Address review comments from Gunter
> Changes in v3:
> - rebase against linux/master
> Changes in v2:
> - apply changes to armada-38x only
> 
>  drivers/watchdog/orion_wdt.c | 66 +++++++++++++++++++++++++++++-------
>  1 file changed, 53 insertions(+), 13 deletions(-)
> 
> diff --git a/drivers/watchdog/orion_wdt.c b/drivers/watchdog/orion_wdt.c
> index cdb0d174c5e2..1cccf8eb1c5d 100644
> --- a/drivers/watchdog/orion_wdt.c
> +++ b/drivers/watchdog/orion_wdt.c
> @@ -35,7 +35,15 @@
>   * Watchdog timer block registers.
>   */
>  #define TIMER_CTRL		0x0000
> -#define TIMER_A370_STATUS	0x04
> +#define TIMER1_FIXED_ENABLE_BIT	BIT(12)
> +#define WDT_AXP_FIXED_ENABLE_BIT BIT(10)
> +#define TIMER1_ENABLE_BIT	BIT(2)
> +
> +#define TIMER_A370_STATUS	0x0004
> +#define WDT_A370_EXPIRED	BIT(31)
> +#define TIMER1_STATUS_BIT	BIT(8)
> +
> +#define TIMER1_VAL_OFF		0x001c
>  
>  #define WDT_MAX_CYCLE_COUNT	0xffffffff
>  
> @@ -43,9 +51,6 @@
>  #define WDT_A370_RATIO_SHIFT	5
>  #define WDT_A370_RATIO		(1 << WDT_A370_RATIO_SHIFT)
>  
> -#define WDT_AXP_FIXED_ENABLE_BIT BIT(10)
> -#define WDT_A370_EXPIRED	BIT(31)
> -
>  static bool nowayout = WATCHDOG_NOWAYOUT;
>  static int heartbeat = -1;		/* module parameter (seconds) */
>  
> @@ -158,6 +163,7 @@ static int armadaxp_wdt_clock_init(struct platform_device *pdev,
>  				   struct orion_watchdog *dev)
>  {
>  	int ret;
> +	u32 val;
>  
>  	dev->clk = of_clk_get_by_name(pdev->dev.of_node, "fixed");
>  	if (IS_ERR(dev->clk))
> @@ -168,10 +174,9 @@ static int armadaxp_wdt_clock_init(struct platform_device *pdev,
>  		return ret;
>  	}
>  
> -	/* Enable the fixed watchdog clock input */
> -	atomic_io_modify(dev->reg + TIMER_CTRL,
> -			 WDT_AXP_FIXED_ENABLE_BIT,
> -			 WDT_AXP_FIXED_ENABLE_BIT);
> +	/* Fix the wdt and timer1 clock freqency to 25MHz */
> +	val = WDT_AXP_FIXED_ENABLE_BIT | TIMER1_FIXED_ENABLE_BIT;
> +	atomic_io_modify(dev->reg + TIMER_CTRL, val, val);
>  
>  	dev->clk_rate = clk_get_rate(dev->clk);
>  	return 0;
> @@ -183,6 +188,10 @@ static int orion_wdt_ping(struct watchdog_device *wdt_dev)
>  	/* Reload watchdog duration */
>  	writel(dev->clk_rate * wdt_dev->timeout,
>  	       dev->reg + dev->data->wdt_counter_offset);
> +	if (dev->wdt.info->options & WDIOF_PRETIMEOUT)
> +		writel(dev->clk_rate * (wdt_dev->timeout - wdt_dev->pretimeout),
> +		       dev->reg + TIMER1_VAL_OFF);
> +
>  	return 0;
>  }
>  
> @@ -194,13 +203,18 @@ static int armada375_start(struct watchdog_device *wdt_dev)
>  	/* Set watchdog duration */
>  	writel(dev->clk_rate * wdt_dev->timeout,
>  	       dev->reg + dev->data->wdt_counter_offset);
> +	if (dev->wdt.info->options & WDIOF_PRETIMEOUT)
> +		writel(dev->clk_rate * (wdt_dev->timeout - wdt_dev->pretimeout),
> +		       dev->reg + TIMER1_VAL_OFF);
>  
>  	/* Clear the watchdog expiration bit */
>  	atomic_io_modify(dev->reg + TIMER_A370_STATUS, WDT_A370_EXPIRED, 0);
>  
>  	/* Enable watchdog timer */
> -	atomic_io_modify(dev->reg + TIMER_CTRL, dev->data->wdt_enable_bit,
> -						dev->data->wdt_enable_bit);
> +	reg = dev->data->wdt_enable_bit;
> +	if (dev->wdt.info->options & WDIOF_PRETIMEOUT)
> +		reg |= TIMER1_ENABLE_BIT;
> +	atomic_io_modify(dev->reg + TIMER_CTRL, reg, reg);
>  
>  	/* Enable reset on watchdog */
>  	reg = readl(dev->rstout);
> @@ -277,7 +291,7 @@ static int orion_stop(struct watchdog_device *wdt_dev)
>  static int armada375_stop(struct watchdog_device *wdt_dev)
>  {
>  	struct orion_watchdog *dev = watchdog_get_drvdata(wdt_dev);
> -	u32 reg;
> +	u32 reg, mask;
>  
>  	/* Disable reset on watchdog */
>  	atomic_io_modify(dev->rstout_mask, dev->data->rstout_mask_bit,
> @@ -287,7 +301,10 @@ static int armada375_stop(struct watchdog_device *wdt_dev)
>  	writel(reg, dev->rstout);
>  
>  	/* Disable watchdog timer */
> -	atomic_io_modify(dev->reg + TIMER_CTRL, dev->data->wdt_enable_bit, 0);
> +	mask = dev->data->wdt_enable_bit;
> +	if (wdt_dev->info->options & WDIOF_PRETIMEOUT)
> +		mask |= TIMER1_ENABLE_BIT;
> +	atomic_io_modify(dev->reg + TIMER_CTRL, mask, 0);
>  
>  	return 0;
>  }
> @@ -349,7 +366,7 @@ static unsigned int orion_wdt_get_timeleft(struct watchdog_device *wdt_dev)
>  	return readl(dev->reg + dev->data->wdt_counter_offset) / dev->clk_rate;
>  }
>  
> -static const struct watchdog_info orion_wdt_info = {
> +static struct watchdog_info orion_wdt_info = {
>  	.options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
>  	.identity = "Orion Watchdog",
>  };
> @@ -368,6 +385,16 @@ static irqreturn_t orion_wdt_irq(int irq, void *devid)
>  	return IRQ_HANDLED;
>  }
>  
> +static irqreturn_t orion_wdt_pre_irq(int irq, void *devid)
> +{
> +	struct orion_watchdog *dev = devid;
> +
> +	atomic_io_modify(dev->reg + TIMER_A370_STATUS,
> +			 TIMER1_STATUS_BIT, 0);
> +	watchdog_notify_pretimeout(&dev->wdt);
> +	return IRQ_HANDLED;
> +}
> +
>  /*
>   * The original devicetree binding for this driver specified only
>   * one memory resource, so in order to keep DT backwards compatibility
> @@ -589,6 +616,19 @@ static int orion_wdt_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	/* Optional 2nd interrupt for pretimeout */
> +	irq = platform_get_irq(pdev, 1);
> +	if (irq > 0) {
> +		orion_wdt_info.options |= WDIOF_PRETIMEOUT;
> +		ret = devm_request_irq(&pdev->dev, irq, orion_wdt_pre_irq,
> +				       0, pdev->name, dev);
> +		if (ret < 0) {
> +			dev_err(&pdev->dev, "failed to request IRQ\n");
> +			goto disable_clk;
> +		}
> +	}
> +
> +
>  	watchdog_set_nowayout(&dev->wdt, nowayout);
>  	ret = watchdog_register_device(&dev->wdt);
>  	if (ret)
> -- 
> 2.23.0
>