Re: Netra X1 with WD0 and AcerIDE

>>> Martin Husemann <martin <at> duskware.de> wrote

> On Mon, Oct 25, 2010 at 10:52:05AM -0400, Chris Ross wrote:
> >   Unless you're wiling to run the disk with PIO.  Which is what I'm 
> > doing on my X1...
> 
> Can we please add a check in the aceride driver for this revision, log
> a prominent warning and go down to PIO mode automatically?
> 
> Martin

FreeBSD's sys/dev/ata/chipsets/ata-acerlabs.c has the following
lines.  It seems using PIO above 137GB but DMA below.

| 	/* only chips with revision > 0xc4 can do 48bit DMA */
| 	if (ctlr->chip->chiprev <= 0xc4)
| 	    device_printf(dev,
| 			  "using PIO transfers above 137GB as workaround for "
| 			  "48bit DMA access bug, expect reduced performance\n");
	:
	:
|     /* older chips can't do 48bit DMA transfers */
|     if (ctlr->chip->chiprev <= 0xc4) {
| 	ch->flags |= ATA_NO_48BIT_DMA;
| 	if (ch->dma.max_iosize > 256 * 512)
| 		ch->dma.max_iosize = 256 * 512;
|     }

-- Takeshi Nakayama