Re: PCI Express

[Colin Ngam <cngam@sgi.com>]

Grant Grundler wrote:

>On Wed, Mar 09, 2005 at 08:35:00AM -0800, Nguyen, Tom L wrote:
>  
>
>>Existing MSI support implements a direct
>>memory-write mechanism (generic solution without platform dependency and
>>limitation to MSI-X support as an example). With existing direct
>>memory-write mechanism, a device's MSI address is configured with
>>current running CPU as a target.
>>    
>>
>
>At some point, PARISC (and Alpha?) will also want to support MSI
>using "direct memory write". But like Altix, does not implement
>0xfeeXXXXX (1) PIB since PARISC arch predates PCI by a decade or so.
>
>We'll have to figure out which platform specific hooks would enable
>parisc/alpha/altix to use existing PCI MSI/MSI-X support.
>
Hi Grant,

Sounds great.

Thanks.

colin

>
>PA-RISC IPI is as straight forward as Jesse described - just write
>to a per CPU address with a data value (vector).
>
>thanks,
>grant
>
>(1) the most recent two or three PA-RISC chipsets do implement 0xfeeXXXXX
>interrupt block. But firmware hands us the CPU "ID/EID" values to use
>when programming the IO SAPIC IRT. See drivers/parisc/iosapic.c
>iosapic_set_irt_data() for more details.
>
>Bottomline is, even if we know it's implemented in HW, we don't know if
>we are using 0xfeeXXXXX or not for IO SAPIC today. platform hooks
>into MSI code would have to sort that out.
>  
>