linux-kernel - Re: about cs5536 interrupt ack

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Date:	Thu, 12 Jul 2007 15:26:07 +0800
From:	Songmao Tian <tiansm@...ote.com>
To:	"Maciej W. Rozycki" <macro@...ux-mips.org>
CC:	LinuxBIOS Mailing List <linuxbios@...uxbios.org>,
	marc.jones@....com, linux-kernel@...r.kernel.org,
	linux-mips@...ux-mips.org
Subject: Re: about cs5536 interrupt ack

8259 problem  seems to be done with the attached patch, IDE hung seems 
to be the dma setting problem.

Thanks all for your advise, comments. I have learned a lot. now I 
continue to trace down the IDE problem.

Mao

Maciej W. Rozycki wrote:
> On Wed, 11 Jul 2007, Songmao Tian wrote:
>
>   
>>> Huh?  Have you managed to find an 8259A clone *that* broken?  So what does
>>> it return if you write 0xc to the address 0x20 in the I/O port space and
>>> then read back from that location?  You should complain to the 
>>>   
>>>       
>> It's the value of IRR, so guess IRR. AMD has well documented cs5536, I
>> appreciate that.
>>     
>
>  Indeed.  I am surprised they have decided to drop the poll command -- it 
> surely does not require much logic as it mostly reuses what's used to 
> produce the vector anyway and it is commonly used when 8259A 
> implementations are interfaced to non-i386 processors.  PPC is another 
> example.
>
>   
>>> More or less -- 3-5 should probably be the outcome of a single read
>>> transaction from the north bridge.  I.e. you issue a read to a "magic"
>>> location, 3-5 happen, and the data value returned is the vector presented by
>>> the interrupt controller on the PCI bus.
>>>   
>>>       
>> yeah, we can implement a register in north bridge.
>>     
>
>  Strictly speaking it would not be a register, but a "PCI INTA address 
> space" much like PCI memory or I/O port address spaces.  Though as the 
> former ignores addresses driven on the bus, the space occupied does not 
> have to be extensive -- I would assume whatever slot size is available 
> with the address decoder you have implemented would do.
>
>   
>>> You can still dispatch interrupts manually by examining the IRR register,
>>> but having a way to ask the 8259A's prioritiser would be nice.  Although
>>> given such a lethal erratum you report I would not count on the prioritiser
>>> to provide any useful flexibility...
>>>   
>>>       
>> yeah, that's a straight thought, tried but failed:(, patch followed.
>>     
>
>  You may have to modify other functions from arch/mips/kernel/i8259.c; 
> yes, this makes the whole experience not as pretty as one would hope...
>
>   Maciej
>
>
>
>   


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