impossible to set pata dma mode?

[Ian Lepore]

On Thu, 2016-01-28 at 09:44 +0100, Norbert Koch wrote:
> Hello.
> 
> I have to reduce dma mode from udma to wdma2
> for a flash device.
> 
> In the past this was easy using atacontrol
> but, afaiks it seems to be impossible using camcontrol.
> 
>  camcontrol negotiate ada0 -M wdma
> ...You can only modify user parameters
> 
>  camcontrol negotiate ada0 -NM wdma
> Works, but I see no way how those user
> parameters become active parameters as the
> driver only reads then in attach as far as
> I can see.
> 
> It seems like the ata driver's interface
> allows to change the current settings
> (XPT_SET_TRAN_SETTINGS/CTS_TYPE_CURRENT_SETTINGS)
> so, why is camcontrol so restrictive?
> 
> Thank you,
> Norbert Koch

I don't know about changing it on the fly with camcontrol (I've never
done that), but you can configure it at boot time with a tunable in
loader.conf of the form

  dev.ada.0.mode="modestr"

Where modestr is one of these (from dev/ata/ata-all.c):

	if (!strcasecmp(str, "PIO0")) return (ATA_PIO0);
	if (!strcasecmp(str, "PIO1")) return (ATA_PIO1);
	if (!strcasecmp(str, "PIO2")) return (ATA_PIO2);
	if (!strcasecmp(str, "PIO3")) return (ATA_PIO3);
	if (!strcasecmp(str, "PIO4")) return (ATA_PIO4);
	if (!strcasecmp(str, "WDMA0")) return (ATA_WDMA0);
	if (!strcasecmp(str, "WDMA1")) return (ATA_WDMA1);
	if (!strcasecmp(str, "WDMA2")) return (ATA_WDMA2);
	if (!strcasecmp(str, "UDMA0")) return (ATA_UDMA0);
	if (!strcasecmp(str, "UDMA16")) return (ATA_UDMA0);
	if (!strcasecmp(str, "UDMA1")) return (ATA_UDMA1);
	if (!strcasecmp(str, "UDMA25")) return (ATA_UDMA1);
	if (!strcasecmp(str, "UDMA2")) return (ATA_UDMA2);
	if (!strcasecmp(str, "UDMA33")) return (ATA_UDMA2);
	if (!strcasecmp(str, "UDMA3")) return (ATA_UDMA3);
	if (!strcasecmp(str, "UDMA44")) return (ATA_UDMA3);
	if (!strcasecmp(str, "UDMA4")) return (ATA_UDMA4);
	if (!strcasecmp(str, "UDMA66")) return (ATA_UDMA4);
	if (!strcasecmp(str, "UDMA5")) return (ATA_UDMA5);
	if (!strcasecmp(str, "UDMA100")) return (ATA_UDMA5);
	if (!strcasecmp(str, "UDMA6")) return (ATA_UDMA6);
	if (!strcasecmp(str, "UDMA133")) return (ATA_UDMA6);

-- Ian