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Message-ID: <0c69734d-b301-7762-7614-0644e2a719ba@roeck-us.net>
Date: Mon, 13 Jul 2020 22:15:41 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Tero Kristo <t-kristo@...com>, wim@...ux-watchdog.org,
linux-watchdog@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, jan.kiszka@...mens.com
Subject: Re: [PATCHv3 3/4] watchdog: rti-wdt: attach to running watchdog
during probe
On 7/13/20 6:18 AM, Tero Kristo wrote:
> If the RTI watchdog is running already during probe, the driver must
> configure itself to match the HW. Window size and timeout is probed from
> hardware, and the last keepalive ping is adjusted to match it also.
>
> Signed-off-by: Tero Kristo <t-kristo@...com>
> ---
> drivers/watchdog/rti_wdt.c | 111 +++++++++++++++++++++++++++++++++----
> 1 file changed, 101 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/watchdog/rti_wdt.c b/drivers/watchdog/rti_wdt.c
> index d456dd72d99a..45dfc546e371 100644
> --- a/drivers/watchdog/rti_wdt.c
> +++ b/drivers/watchdog/rti_wdt.c
> @@ -35,7 +35,11 @@
>
> #define RTIWWDRX_NMI 0xa
>
> -#define RTIWWDSIZE_50P 0x50
> +#define RTIWWDSIZE_50P 0x50
> +#define RTIWWDSIZE_25P 0x500
> +#define RTIWWDSIZE_12P5 0x5000
> +#define RTIWWDSIZE_6P25 0x50000
> +#define RTIWWDSIZE_3P125 0x500000
>
> #define WDENABLE_KEY 0xa98559da
>
> @@ -48,7 +52,7 @@
>
> #define DWDST BIT(1)
>
> -static int heartbeat;
> +static int heartbeat = DEFAULT_HEARTBEAT;
>
> /*
> * struct to hold data for each WDT device
> @@ -79,11 +83,9 @@ static int rti_wdt_start(struct watchdog_device *wdd)
> * be petted during the open window; not too early or not too late.
> * The HW configuration options only allow for the open window size
> * to be 50% or less than that; we obviouly want to configure the open
> - * window as large as possible so we select the 50% option. To avoid
> - * any glitches, we accommodate 5% safety margin also, so we setup
> - * the min_hw_hearbeat at 55% of the timeout period.
> + * window as large as possible so we select the 50% option.
> */
> - wdd->min_hw_heartbeat_ms = 11 * wdd->timeout * 1000 / 20;
> + wdd->min_hw_heartbeat_ms = 500 * wdd->timeout;
>
> /* Generate NMI when wdt expires */
> writel_relaxed(RTIWWDRX_NMI, wdt->base + RTIWWDRXCTRL);
> @@ -110,7 +112,48 @@ static int rti_wdt_ping(struct watchdog_device *wdd)
> return 0;
> }
>
> -static unsigned int rti_wdt_get_timeleft(struct watchdog_device *wdd)
> +static int rti_wdt_setup_hw_hb(struct watchdog_device *wdd, u32 wsize)
> +{
> + /*
> + * RTI only supports a windowed mode, where the watchdog can only
> + * be petted during the open window; not too early or not too late.
> + * The HW configuration options only allow for the open window size
> + * to be 50% or less than that.
> + */
> + switch (wsize) {
> + case RTIWWDSIZE_50P:
> + /* 50% open window => 50% min heartbeat */
> + wdd->min_hw_heartbeat_ms = 500 * heartbeat;
> + break;
> +
> + case RTIWWDSIZE_25P:
> + /* 25% open window => 75% min heartbeat */
> + wdd->min_hw_heartbeat_ms = 750 * heartbeat;
> + break;
> +
> + case RTIWWDSIZE_12P5:
> + /* 12.5% open window => 87.5% min heartbeat */
> + wdd->min_hw_heartbeat_ms = 875 * heartbeat;
> + break;
> +
> + case RTIWWDSIZE_6P25:
> + /* 6.5% open window => 93.5% min heartbeat */
> + wdd->min_hw_heartbeat_ms = 935 * heartbeat;
> + break;
> +
> + case RTIWWDSIZE_3P125:
> + /* 3.125% open window => 96.9% min heartbeat */
> + wdd->min_hw_heartbeat_ms = 969 * heartbeat;
> + break;
> +
> + default:
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +static unsigned int rti_wdt_get_timeleft_ms(struct watchdog_device *wdd)
> {
> u64 timer_counter;
> u32 val;
> @@ -123,11 +166,18 @@ static unsigned int rti_wdt_get_timeleft(struct watchdog_device *wdd)
>
> timer_counter = readl_relaxed(wdt->base + RTIDWDCNTR);
>
> + timer_counter *= 1000;
> +
> do_div(timer_counter, wdt->freq);
>
> return timer_counter;
> }
>
> +static unsigned int rti_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> + return rti_wdt_get_timeleft_ms(wdd) / 1000;
> +}
> +
> static const struct watchdog_info rti_wdt_info = {
> .options = WDIOF_KEEPALIVEPING,
> .identity = "K3 RTI Watchdog",
> @@ -148,6 +198,7 @@ static int rti_wdt_probe(struct platform_device *pdev)
> struct watchdog_device *wdd;
> struct rti_wdt_device *wdt;
> struct clk *clk;
> + u32 last_ping = 0;
>
> wdt = devm_kzalloc(dev, sizeof(*wdt), GFP_KERNEL);
> if (!wdt)
> @@ -169,6 +220,14 @@ static int rti_wdt_probe(struct platform_device *pdev)
> return -EINVAL;
> }
>
> + /*
> + * If watchdog is running at 32k clock, it is not accurate.
> + * Adjust frequency down in this case so that we don't pet
> + * the watchdog too often.
> + */
> + if (wdt->freq < 32768)
> + wdt->freq = wdt->freq * 9 / 10;
> +
So this is now only a problem is the window size was set restrictively
in the BOS/ROMMON. Meaning it is still a problem. How is this better than
before ? Why not just always set the window size to something reasonable ?
> pm_runtime_enable(dev);
> ret = pm_runtime_get_sync(dev);
> if (ret) {
> @@ -185,11 +244,8 @@ static int rti_wdt_probe(struct platform_device *pdev)
> wdd->min_timeout = 1;
> wdd->max_hw_heartbeat_ms = (WDT_PRELOAD_MAX << WDT_PRELOAD_SHIFT) /
> wdt->freq * 1000;
> - wdd->timeout = DEFAULT_HEARTBEAT;
> wdd->parent = dev;
>
> - watchdog_init_timeout(wdd, heartbeat, dev);
> -
> watchdog_set_drvdata(wdd, wdt);
> watchdog_set_nowayout(wdd, 1);
> watchdog_set_restart_priority(wdd, 128);
> @@ -201,12 +257,47 @@ static int rti_wdt_probe(struct platform_device *pdev)
> goto err_iomap;
> }
>
> + if (readl(wdt->base + RTIDWDCTRL) == WDENABLE_KEY) {
> + u32 time_left_ms;
> + u64 heartbeat_ms;
> + u32 wsize;
> +
> + set_bit(WDOG_HW_RUNNING, &wdd->status);
> + time_left_ms = rti_wdt_get_timeleft_ms(wdd);
> + heartbeat_ms = readl(wdt->base + RTIDWDPRLD);
> + heartbeat_ms <<= WDT_PRELOAD_SHIFT;
> + heartbeat_ms *= 1000;
> + heartbeat_ms /= wdt->freq;
Ah yes, the pitfalls of 64-bit divide operations.
> + if (heartbeat_ms / 1000 != heartbeat)
> + dev_warn(dev, "watchdog already running, ignoring heartbeat config!\n");
> +
> + heartbeat = heartbeat_ms / 1000;
> +
> + wsize = readl(wdt->base + RTIWWDSIZECTRL);
> + ret = rti_wdt_setup_hw_hb(wdd, wsize);
> + if (ret) {
> + dev_err(dev, "bad window size.\n");
> + goto err_iomap;
> + }
> +
> + last_ping = heartbeat_ms - time_left_ms;
> + if (time_left_ms > heartbeat_ms) {
> + dev_warn(dev, "time_left > heartbeat? Assuming last ping just before now.\n");
> + last_ping = 0;
> + }
All that complexity makes me wonder if it wouldn't be better to just reprogram
the watchdog if it is already running. Any reason for not doing that ?
> + }
> +
> + watchdog_init_timeout(wdd, heartbeat, dev);
> +
> ret = watchdog_register_device(wdd);
> if (ret) {
> dev_err(dev, "cannot register watchdog device\n");
> goto err_iomap;
> }
>
> + if (last_ping)
> + watchdog_set_last_hw_keepalive(wdd, last_ping);
> +
> return 0;
>
> err_iomap:
>
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