Re: IO port conflict between timer & watchdog on PCISA-C800EV board?

[linux-os]

On Mon, 7 Feb 2005, Randy.Dunlap wrote:

> Charles-Edouard Ruault wrote:
> > Hi All,
> >
> > i wrote a driver for the watchdog timer provided by a small form factor 
> > board from IEI ( the PCISA-C800EV : 
> > http://www.iei.com.tw/en/product_IPC.asp?model=PCISA-C800 ).
> > This board has a Via Apollo PLE133 ( VT8601A and VT82C686B ) chipset.
> > The watchdog uses two registers at addresses 0x43 and 0x443, therefore my 
> > driver tries to get bot addresses for its own use calling
> > request_region(0x43, 1, "watchdog" ) and request_region(0x443, 1, 
> > "watchdog").
> > The first call to request 0x43 fails because the address has already been 
> > allocated to the timer ( /proc/ioports shows 0040-005f : timer ).
> >
> > So my questions are :
> > - Why is the generic timer using this address ? isn't it reserving a too 
> > wide portion of IO ports ? Should it be modified for this board ?
> > -  If there's a good reason for the timer to request this address, is 
> > there a clean way to share it with the timer ?
>
> Missing kernel version.... must be "not the current/latest",
> so early 2.6 or more likely 2.4 (just guessing)?
>
> /proc/ioports timer assignments have now been split up like this:
> 0040-0043 : timer0
> 0050-0053 : timer1
>
> However, port 0x43 is still assigned to timer0, so your request_region
> call will still fail.  What system board timer resource assignments
> should be used for that VIA chipset?  If the chipset timer only needs
> 0x40-0x42, e.g., leaving 0x43 available, then it would be possible
> to do some kind of workaround (maybe not real clean, but possible).
>
> --
> ~Randy

The driver can still R/W registers that it hasn't allocated.
There is no hardware trap preventing this. I suggest that,
as a temporary work-around, just don't allocate the low
port, but attempt to use it. I think the watchdog probably
just looks for read at that address.


Cheers,
Dick Johnson
Penguin : Linux version 2.6.10 on an i686 machine (5537.79 BogoMips).
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