Re: what is hdparm doing?

[Sebastian Kuzminsky <seb@highlab.com>]

Mark Lord <liml@rtr.ca> wrote:
> Sebastian Kuzminsky wrote:
> > Hi folks, hdparm's got me confused.
> ..
> > "hdparm /dev/hda" says:
> .
> >             DMA: mdma0 mdma1 *mdma2
> >                  Cycle time: min=120ns recommended=120ns
> >             PIO: pio0 pio1 pio2 pio3 pio4
> >                  Cycle time: no flow control=120ns  IORDY flow control=120ns
> ..
> 
> The *mdma2 means, that if you were to issue a READ_DMA (or WRITE_DMA)
> command to the drive, the drive is expecting the host to use
> the multiword-dma-2 protocol and timings for it.
> 
> Meanwhile, the host may, at its option, simply use PIO commands (READ, WRITE)
> instead of DMA, any time it chooses.
> 
> Drives have both a DMA mode, and a PIO mode, each of which is selected
> and used independently of the other.

Ok thanks!

So how do I know what PIO mode the drive wants to use?

And how do I tell the HBA what PIO mode to use?

-- 
Sebastian Kuzminsky