Linux-compatible watchdog add-on?

Linux-compatible watchdog add-on?

[Nicolas Boullis]

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Hi,

Sorry if my question is off-topic for this list.

I have a computer that experienced a kernel failure while a was far away 
and nobody could reboot it. So I thought it would be nice to have a 
watchdog. Unfortunately, to the best of my knowledge, it has no hardware 
watchdog, so I thought I should add one.

Hence, do you have suggestions for I²C-, serial- or USB-connected 
watchdog add-ons? It should of course be compatible with linux.

I found 
  http://www.berkprod.com/Product_Web_Pages/usb_v1_pc_watchdog.aspx
but I think it is a little too expensive.

If no such thing exists, I might consider designing my own (open 
hardware) I²C- or USB-connected watchdog add-on, using a cheap MCU. But 
then I would welcome opinions on what the interface between the host and 
watchdog should look like.


Cheers,

-- 
Nicolas Boullis

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Re: Linux-compatible watchdog add-on?

[Oleksij Rempel]

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Hi

Am 25.08.2016 um 18:31 schrieb Nicolas Boullis:
> Hi,
> 
> Sorry if my question is off-topic for this list.
> 
> I have a computer that experienced a kernel failure while a was far away 
> and nobody could reboot it. So I thought it would be nice to have a 
> watchdog. Unfortunately, to the best of my knowledge, it has no hardware 
> watchdog, so I thought I should add one.
> 
> Hence, do you have suggestions for I²C-, serial- or USB-connected 
> watchdog add-ons? It should of course be compatible with linux.
> 
> I found 
>   http://www.berkprod.com/Product_Web_Pages/usb_v1_pc_watchdog.aspx
> but I think it is a little too expensive.
> 
> If no such thing exists, I might consider designing my own (open 
> hardware) I²C- or USB-connected watchdog add-on, using a cheap MCU. But 
> then I would welcome opinions on what the interface between the host and 
> watchdog should look like.

How about SPI?
If yes, you can try this project:
https://plus.google.com/102032716864870215256/posts/PwMMKYP5PKR
https://plus.google.com/102032716864870215256/posts/QJqPxSi1Str

Linux side is configured as watchdog, MCU side currently do only demo
blinking, but watchdog should be a main future.


-- 
Regards,
Oleksij


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Re: Linux-compatible watchdog add-on?

[Nicolas Boullis]

Hi,

On Fri, Aug 26, 2016 at 06:58:15AM +0200, Oleksij Rempel wrote:
> 
> How about SPI?
> If yes, you can try this project:
> https://plus.google.com/102032716864870215256/posts/PwMMKYP5PKR
> https://plus.google.com/102032716864870215256/posts/QJqPxSi1Str
> 
> Linux side is configured as watchdog, MCU side currently do only demo
> blinking, but watchdog should be a main future.

Thanks for telling me about this project.

But, to be honnest, I don’t really understand what this project is 
about. I never hearded about the SSI32 protocol (while I know the SPI 
protocol)…

Anyway, as far as I know, my motherboard has no SPI bus… I guess I might 
buy or design an USB-SPI interface, but I wonder if designing an USB 
watchdog wouldn’t be easier…

Anyway, I would still be interested to understand a little more what 
that project is about; it might at least be a good source for 
inspiration…


Cheers,

-- 
Nicolas Boullis
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Re: Linux-compatible watchdog add-on?

[Oleksij Rempel]

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Hi

Am 27.08.2016 um 01:14 schrieb Nicolas Boullis:
> Hi,
> 
> On Fri, Aug 26, 2016 at 06:58:15AM +0200, Oleksij Rempel wrote:
>>
>> How about SPI?
>> If yes, you can try this project:
>> https://plus.google.com/102032716864870215256/posts/PwMMKYP5PKR
>> https://plus.google.com/102032716864870215256/posts/QJqPxSi1Str
>>
>> Linux side is configured as watchdog, MCU side currently do only demo
>> blinking, but watchdog should be a main future.
> 
> Thanks for telling me about this project.
> 
> But, to be honnest, I don’t really understand what this project is 
> about. I never hearded about the SSI32 protocol (while I know the SPI 
> protocol)…
> 
> Anyway, as far as I know, my motherboard has no SPI bus… I guess I might 
> buy or design an USB-SPI interface, but I wonder if designing an USB 
> watchdog wouldn’t be easier…
> 
> Anyway, I would still be interested to understand a little more what 
> that project is about; it might at least be a good source for 
> inspiration…
>
This project have different components levels:
1. SPI - it is cheap any mostly available on all SoCs and MCUs. IMO same
can be implemented on UART.
2. Flow control line. SPI don't have it and if we use  MCU with many
tasks on other end, there is no way to predict where we can start our
transfer. The are many ways to implement flow control on SPI, some of
them implemented directly to IPcore which is not really portable.
3. Request/Interrupt line is muxed with Flow Control, it means by using
5 wire we still able to do slave to master transfer and flow control.
4. on transport level it has 4 byte header with some control
information, size and checksumming. Practice has show that even on
stable products we can get some weard DMA or FIFO related bugs so the
transfer got corrupted.
4. LUN or Endpoint number, so one MCU can provide different functions at
same time. For example watchdog, rtc clock, package filter, gpio
extender. At same time since it all done in software we can use unified
linux drivers.
5. App to App acknowledgement, so each side knows if package was
actually delivered.
6. linux side bus implementation, so on linux we create a device tree
with MCU capabilities and drivers are loaded automatically.

In my link i provided a example watchdog driver, but in this case MCU is
only toggling LEDs. Need more time to finish it.

-- 
Regards,
Oleksij


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Re: Linux-compatible watchdog add-on?

[Guenter Roeck]

On Thu, Aug 25, 2016 at 06:31:49PM +0200, Nicolas Boullis wrote:
> Hi,
> 
> Sorry if my question is off-topic for this list.
> 
> I have a computer that experienced a kernel failure while a was far away 
> and nobody could reboot it. So I thought it would be nice to have a 
> watchdog. Unfortunately, to the best of my knowledge, it has no hardware 
> watchdog, so I thought I should add one.
> 
> Hence, do you have suggestions for I²C-, serial- or USB-connected 
> watchdog add-ons? It should of course be compatible with linux.
> 
> I found 
>   http://www.berkprod.com/Product_Web_Pages/usb_v1_pc_watchdog.aspx
> but I think it is a little too expensive.
> 
> If no such thing exists, I might consider designing my own (open 
> hardware) I²C- or USB-connected watchdog add-on, using a cheap MCU. But 
> then I would welcome opinions on what the interface between the host and 
> watchdog should look like.
> 
Anything you come up with will need a connection to the system reset,
so you'll have to have an in-chassis solution. Any cheap MCU with USB
or I2C port and a couple of GPIO ports would probably do.

If you consider the above product, make sure that you get an assurance
that its Linux driver still works - it is quite old.

Guenter