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    SubjectRe: [PATCH v10 5/5] Watchdog: ARM SBSA Generic Watchdog half timeout panic support
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    On 02/06/2016 10:02 AM, Fu Wei wrote:
    > Hi Guenter,
    >
    > On 6 February 2016 at 07:54, Guenter Roeck <linux@roeck-us.net> wrote:
    >> On 02/05/2016 10:21 AM, Fu Wei wrote:
    >>>
    >>> On 5 February 2016 at 22:42, Guenter Roeck <linux@roeck-us.net> wrote:
    >>>>
    >>>> On 02/05/2016 01:51 AM, Fu Wei wrote:
    >>>>>
    >>>>>
    >>>>> Hi Guenter,
    >>>>>
    >>>>> On 4 February 2016 at 13:17, Guenter Roeck <linux@roeck-us.net> wrote:
    >>>>>>
    >>>>>>
    >>>>>> On 02/03/2016 03:00 PM, Fu Wei wrote:
    >>>>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>> On 4 February 2016 at 02:45, Timur Tabi <timur@codeaurora.org> wrote:
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>> Fu Wei wrote:
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>>
    >>>>>>>>> As you know I have made the pre-timeout support patch, If people
    >>>>>>>>> like
    >>>>>>>>> it, i am happy to go on upstream it separately.
    >>>>>>>>>
    >>>>>>>>> If we want to use pre-timeout here, user only can use get_pretimeout
    >>>>>>>>> and disable panic by setting pretimeout to 0
    >>>>>>>>> but user can not really set pretimeout, because "pre-timeout ==
    >>>>>>>>> timeout / 2 (always)".
    >>>>>>>>> if user want to change pretimeout, he/she has to set_time instead.
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>>
    >>>>>>>> Ok, I think patches 4 and 5 should be combined, and I think the
    >>>>>>>> Kconfig
    >>>>>>>> entry should be removed and just use panic_enabled.
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>>
    >>>>>> Agreed.
    >>>>>
    >>>>>
    >>>>>
    >>>>> np, will do
    >>>>>
    >>>>>>>
    >>>>>>>
    >>>>>>> NP, will update this patchset like that , thanks :-)
    >>>>>>>
    >>>>>>
    >>>>>> Also, if panic is enabled, the timeout needs to be adjusted accordingly
    >>>>>> (to only panic after the entire timeout period has expired, not after
    >>>>>> half of it). We can not panic the system after timeout / 2.
    >>>>>
    >>>>>
    >>>>>
    >>>>> OK, my thought is
    >>>>>
    >>>>> if panic is enabled :
    >>>>> |--------WOR-------WS0--------WOR-------WS1
    >>>>> |------timeout------(panic)------timeout-----reset
    >>>>>
    >>>>> if panic is disabled .
    >>>>> |--------WOR-------WS0--------WOR-------WS1
    >>>>> |---------------------timeout---------------------reset
    >>>>>
    >>>>> panic_enabled only can be configured when module is loaded by module
    >>>>> parameter
    >>>>>
    >>>>> But user should know that max_timeout(panic_enable) =
    >>>>> max_timeout(panic_disable) / 2
    >>>>>
    >>>>
    >>>> That means you'll have to update max_timeout accordingly.
    >>>
    >>>
    >>> panic_enabled only can be configured when module is loaded, so we
    >>> don't need to update it.
    >>>
    >>> max_timeout will only be set up in the init stage.
    >>>
    >>> Does it make sense ? :-)
    >>>
    >> Not sure I understand your problem or question.
    >>
    >> max_timeout will have to reflect the correct maximum timeout, under
    >> all circumstances. It will have to be set to the correct value before
    >> the watchdog driver is registered.
    >
    > yes, understood, my thought is :
    >
    > in static int sbsa_gwdt_probe(struct platform_device *pdev)
    >
    > if (action) {
    > wdd->min_timeout = 1;
    > wdd->max_timeout = U32_MAX / gwdt->clk;
    > } else {
    > wdd->min_timeout = 2;
    > wdd->max_timeout = U32_MAX / gwdt->clk * 2;

    Pretty much, though you would also have to adjust all calculations
    using gwdt->clk, in both set_timeout() and get_timeout(). Wonder if
    you could adjust gwdt->clk instead.

    Does min_timeout really have to be 2 if panic is disabled ?
    The only reason seems to be the calculation in sbsa_gwdt_set_timeout().

    writel(timeout / 2 * gwdt->clk, gwdt->control_base + SBSA_GWDT_WOR);

    Maybe you could use something like

    writel(timeout * (gwdt->clk / 2), ...);

    instead. Or, as mentioned above, adjust the value of gwdt->clk
    to include the factor.

    Thanks,
    Guenter

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