Messages in this thread |  | | Date | Mon, 08 Jun 2015 11:26:16 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH v4 5/7] Watchdog: introduce ARM SBSA watchdog driver |
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On 06/08/2015 09:05 AM, Fu Wei wrote: > Hi Gurnter > > On 3 June 2015 at 01:07, Guenter Roeck <linux@roeck-us.net> wrote: >> On 06/02/2015 09:55 AM, Fu Wei wrote: >>> >>> Hi Timur, >>> >>> Thanks , feedback inline >>> >>> On 2 June 2015 at 23:32, Timur Tabi <timur@codeaurora.org> wrote: >>>> >>>> On 06/01/2015 11:05 PM, fu.wei@linaro.org wrote: >>>> >>>>> +/* >>>>> + * help functions for accessing 32bit registers of SBSA Generic >>>>> Watchdog >>>>> + */ >>>>> +static void sbsa_gwdt_cf_write(unsigned int reg, u32 val, >>>>> + struct watchdog_device *wdd) >>>>> +{ >>>>> + struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd); >>>>> + >>>>> + writel_relaxed(val, gwdt->control_base + reg); >>>>> +} >>>>> + >>>>> +static void sbsa_gwdt_rf_write(unsigned int reg, u32 val, >>>>> + struct watchdog_device *wdd) >>>>> +{ >>>>> + struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd); >>>>> + >>>>> + writel_relaxed(val, gwdt->refresh_base + reg); >>>>> +} >>>>> + >>>>> +static u32 sbsa_gwdt_cf_read(unsigned int reg, struct watchdog_device >>>>> *wdd) >>>>> +{ >>>>> + struct sbsa_gwdt *gwdt = to_sbsa_gwdt(wdd); >>>>> + >>>>> + return readl_relaxed(gwdt->control_base + reg); >>>>> +} >>>> >>>> >>>> >>>> I still think you should get rid of these functions and just call >>>> readl_relaxed() and writel_relaxed() every time, but I won't complain >>>> again >>>> if you keep them. >>> >>> >>> yes, that make sense, and will reduce the size of code, and I think >>> the code's readability will be OK too. >>> will try in my next patch, >>> >>>> >>>>> +static irqreturn_t sbsa_gwdt_interrupt(int irq, void *dev_id) >>>>> +{ >>>>> + struct sbsa_gwdt *gwdt = (struct sbsa_gwdt *)dev_id; >>>>> + struct watchdog_device *wdd = &gwdt->wdd; >>>>> + >>>>> + if (wdd->pretimeout) >>>>> + /* The pretimeout is valid, go panic */ >>>>> + panic("SBSA Watchdog pre-timeout"); >>>>> + else >>>>> + /* We don't use pretimeout, trigger WS1 now*/ >>>>> + sbsa_gwdt_set_wcv(wdd, 0); >>>> >>>> >>>> >>>> I don't like this. >>> >>> >>> If so, what is your idea ,if pretimeout == 0? >>> >>> the reason of using WCV as (timout - pretimeout): it can provide the >>> longer timeout period, >>> (1)If we use WOR, it can only provide 10s @ 400MHz(max). >>> as Guenter said earlier, the default timer out for most watchdog will >>> be 30s, so I think 10s limit will be a little short >>> (2)we can always program WCV just like ping. >>> (3)if a timeout arrives, WOR will be use, so use it as pretimeout, but >>> we still can make this pretimeout longer by programming WCV(I don't >>> think it's necessary) >>> >>> >>>> The triggering of the hardware reset should never depend >>>> on an interrupt being handled properly. >>> >>> >>> if this fail, system reset in 1S, because WOR == (1s) >>> >> So ? > > Even the interrupt routine isn't triggered, (WOR + system counter) --> WCV, > then, sy system reset in 1S. > > the hardware reset doesn't depend on an interrupt. > > >> >>>> You should always program WCV >>>> correctly in advance. This is especially true since pre-timeout will >>>> probably rarely be used. >>> >>> >>> always programming WCV is doable. But I absolutely can not agree " >>> pre-timeout will probably rarely be used" >>> If so, SBSA watchdog is just a normal watchdog, This use case just >>> makes this HW useless. >>> If so, go to use SP805. >>> you still don't see the importance of this warning and pretimeout to a >>> real server. >>> >> >> If pretimeout isn't used, why not just set WCV = timeout, WOR = 0 ? > > Because if WOR = 0 , according to SBSA, once you want to enable watchdog, > (0 + system counter) --> WCV , then , WS0 and WS1 will be triggered immediately. > we have not a chance(a time slot) to update WCV. >
I would have thought that this is exactly what we want if pretimeout is not used. What am I missing here ?
Guenter
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