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Message-ID: <ef5d2227-90ad-19d4-5d40-5cd21c669266@roeck-us.net>
Date: Thu, 29 Aug 2019 05:34:15 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Chris Packham <Chris.Packham@...iedtelesis.co.nz>,
"wim@...ux-watchdog.org" <wim@...ux-watchdog.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-watchdog@...r.kernel.org" <linux-watchdog@...r.kernel.org>
Subject: Re: [PATCH v4] watchdog: orion_wdt: use timer1 as a pretimeout
On 8/28/19 10:05 PM, Chris Packham wrote:
> On Wed, 2019-08-28 at 21:45 -0700, Guenter Roeck wrote:
>> On 8/28/19 6:53 PM, 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@...iedtelesis.co.nz>
>>> ---
>>>
>>> This was submitted previously[1], the other patches two from the series have
>>> been picked up but this one seems to have fallen through the gaps.
>>>
>>
>> I had marked it as "under review" but I don't recall why. Maybe it was because
>> it depended on the other patches, but I don't recall, and I didn't keep track
>> of those patches either. Sorry for that.
>>
>
> No problem. I think it was related to discussions around the other
> patches. I had meant to follow up earlier.
>
>>> Changes in v3:
>>> - rebase against linux/master
>>> Changes in v2:
>>> - apply changes to armada-38x only
>>>
>>> [1] - https://lore.kernel.org/linux-watchdog/20190305201924.14853-4-chris.packham@alliedtelesis.co.nz/
>>>
>>> drivers/watchdog/orion_wdt.c | 59 ++++++++++++++++++++++++++++++------
>>> 1 file changed, 50 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/watchdog/orion_wdt.c b/drivers/watchdog/orion_wdt.c
>>> index cdb0d174c5e2..f2e90bfd7186 100644
>>> --- a/drivers/watchdog/orion_wdt.c
>>> +++ b/drivers/watchdog/orion_wdt.c
>>> @@ -46,6 +46,11 @@
>>> #define WDT_AXP_FIXED_ENABLE_BIT BIT(10)
>>> #define WDT_A370_EXPIRED BIT(31)
>>>
>>> +#define TIMER1_VAL_OFF 0x001c
>>> +#define TIMER1_ENABLE_BIT BIT(2)
>>> +#define TIMER1_FIXED_ENABLE_BIT BIT(12)
>>> +#define TIMER1_STATUS_BIT BIT(8)
>>> +
>>
>> It would be better to group the bits associated with a single register together.
>> The bits above are not associated with TIMER1_VAL_OFF, yet the grouping suggests
>> that this may be the case.
>
> Will fix.
>
>>
>>> 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))
>>> @@ -169,38 +175,48 @@ static int armadaxp_wdt_clock_init(struct platform_device *pdev,
>>> }
>>>
>>> /* Enable the fixed watchdog clock input */
>>> - atomic_io_modify(dev->reg + TIMER_CTRL,
>>> - WDT_AXP_FIXED_ENABLE_BIT,
>>> - WDT_AXP_FIXED_ENABLE_BIT);
>>> + val = WDT_AXP_FIXED_ENABLE_BIT | TIMER1_FIXED_ENABLE_BIT;
>>
>> This always sets TIMER1_FIXED_ENABLE_BIT, but later the enable bit is set
>> only conditionally. I don't know what is correct, but this asks for a comment.
>
> The fixed part is safe to set. It just means that the rate is constant.
> I'll add a comment.
>
>>
>>> + atomic_io_modify(dev->reg + TIMER_CTRL, val, val);
>>>
>>> dev->clk_rate = clk_get_rate(dev->clk);
>>> +
>>
>> We can only hope we won't see another patch two days from now where someone
>> removes this added line.
>>
>> I can understand such changes if they fix a checkpatch issue,
>> but otherwise please refrain from whitespace changes.
>
> I think it was to appease checkpatch, the one below certainly was. If
> it's not needed for checkpatch I'll drop it in the next version.
>
>>
>>> return 0;
>>> }
>>>
>>> static int orion_wdt_ping(struct watchdog_device *wdt_dev)
>>> {
>>> struct orion_watchdog *dev = watchdog_get_drvdata(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;
>>> }
>>>
>>> static int armada375_start(struct watchdog_device *wdt_dev)
>>> {
>>> struct orion_watchdog *dev = watchdog_get_drvdata(wdt_dev);
>>> - u32 reg;
>>> + u32 reg, val;
>>>
>>
>> Is the second variable here and below really necessary ?
>>
>
> No I can use reg.
>
>>> /* 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);
>>> + val = dev->data->wdt_enable_bit;
>>> + if (dev->wdt.info->options & WDIOF_PRETIMEOUT)
>>> + val |= TIMER1_ENABLE_BIT;
>>> + atomic_io_modify(dev->reg + TIMER_CTRL, val, val);
>>>
>>> /* Enable reset on watchdog */
>>> reg = readl(dev->rstout);
>>> @@ -277,7 +293,7 @@ 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 +303,10 @@ 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;
>>
>> FWIW, += is a bit unusual for a mask. Is it guaranteed that
>> the bit is never already set ? Any special reason for using +=
>> instead of |= here, but not above ?
>>
>
> I have no idea why on earth I used +=, slip of the keyboard perhaps, |=
> is obviously the correct thing to use.
>
>>> + atomic_io_modify(dev->reg + TIMER_CTRL, mask, 0);
>>>
>>> return 0;
>>> }
>>> @@ -349,7 +368,7 @@ 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 +387,16 @@ 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 +618,18 @@ static int orion_wdt_probe(struct platform_device *pdev)
>>> }
>>> }
>>>
>>> + irq = platform_get_irq(pdev, 1);
>>
>> platform_get_irq() may return -EPROBE_DEFER. Are you sure you want to ignore
>> the interrupt (and thus disable the pretimeout) if that is the case ?
>>
>
> In any current system that uses this driver I can't imagine a case
> where we would see -EPROBE_DEFER here and not for the index 0 interrupt
> above. And even then these are SoC interrupt sources so it's unlikely
> that they would be deferred.
>
> I do need to handle the case where the 2nd irq is not provided (which
> is what I was going for here). IMHO I think it's better to get on with
> things rather than deferring the entire driver probe just because an
> optional feature isn't ready for use. But if you want me to handle
> -EPROBE_DEFER here I will.
>
Your call, but maybe add a comment to avoid future questions.
Thanks,
Guenter
>>> + 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)
>>>
>>
>>
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