RELENG_7: interrupt eating whole cpu core

[Tom Evans]

On Tue, 2008-02-12 at 15:53 +0100, Oliver Fromme wrote:
> Tom Evans wrote:
>  > The chipset supports UDMA6, the drive supports UDMA6,
> 
> Are you sure about that?  What brand/model is that?
> I don't think I've ever seen an atapi CD/DVD drive
> that supported more than UDMA3.
> 
> Best regards
>    Oliver
> 
I actually made a mistake there; the drive supports 'ATA/ATAPI Revision
6', which is, of course, UDMA5. This is according to atacontrol, and is
used when booted up into windows 2000. 

I believe UDMA modes will give less resource usage compared to WDMA
modes, and combined with a large read-ahead cache in mplayer, should
prolong battery life by spinning up less frequently and remaining
spinning for less time, therefore I'm going to continue to try and get
it to correctly allow my DVD drive to use these modes. 

As for drives not supporting more than udma3, seems ok on linux.

/dev/hda:

ATAPI CD-ROM, with removable media
        Model Number:       PIONEER DVD-RW  DVR-112                 
        Serial Number:      GFDP176727WL       
        Firmware Revision:  1.21    
Standards:
        Likely used CD-ROM ATAPI-1
Configuration:
        DRQ response: 50us.
        Packet size: 12 bytes
Capabilities:
        LBA, IORDY(can be disabled)
        Buffer size: 64.0kB
        DMA: mdma0 mdma1 mdma2 udma0 udma1 udma2 udma3 *udma4 
             Cycle time: min=120ns recommended=120ns
        PIO: pio0 pio1 pio2 pio3 pio4 
             Cycle time: no flow control=240ns  IORDY flow control=120ns

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