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Message-ID: <2a92083c-f8bd-7a42-25e2-ee6ae354a4de@ti.com>
Date: Tue, 14 Jul 2020 09:50:22 +0300
From: Tero Kristo <t-kristo@...com>
To: Guenter Roeck <linux@...ck-us.net>, <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 14/07/2020 08:15, Guenter Roeck wrote:
> 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 ?
Re-programming of the watchdog only takes effect at the next ping, then
and only then will it adjust the window size + timeout period.
>
>
>> 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.
Should I convert this to use do_div? With 64bit archs this code is
targeted at it runs just fine.
>
>> + 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 ?
Well, you can re-program it but... It does not take effect until next
window starts, so basically we need to take care of the currently
running window anyways after which re-programming it doesn't make much
sense anymore. And handling the switch from one setup to next would add
extra complexity.
-Tero
>
>> + }
>> +
>> + 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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