enabling DMA in FreeBSD

Hecate

I'm trying to enable DMA mode for two drives in FreeBSD (one cdrw and one dvd).

The DVD drive is master on the 2nd ide channel and the cdrw is a slave; they're both currently in programmed io mode:

acd0: DVD-ROM <TOSHIBA DVD-ROM SD-M1202> at ata1-master PIO4

acd1: CD-RW <CR-4804TE> at ata1-slave PIO3

Now i've tried setting DMA with sysctl hw.ata.atapi_dma=1 but it says the variable is read only, wont do it through single user mode or sysctl.conf either

Any one managed to get this working?..the drives run in DMA mode in windows so I'm pretty sure they supoort it.

(running FreeBSD 4.8)

QBall

AFAIK you can set hw.ata.atapi_dma from /boot/loader.conf

Also, I'm not 100% sure but you may have to quote the 1 when you put it in loader.conf. (i.e. hw.ata.atapi_dma="1")

/me goes off to look at the docs again...

[edit]
atacontrol(8) may be what you're looking for.
[/edit]

hamster

Not sure about FreeBsd but generally:

hdparm -d1 device_of_your_drive_that_supplies_video_data

similar line here: http://oreilly.linux.com/pub/a/linu.../29/hdparm.html

QBall

AFAIK FreeBSD has no hdparm. (It's not on my copy of FreeBSD 5.0 and www.freebsd.org doesn't have a man page for it.)

You use the sysctls and/or atacontrol(8).

Then again, I've never gone about enabling DMA on my machine, mainly cos I don't really need it, so I may be open to correction.

Hecate

Yep atacontrol seemed to work fine.

Typedef

Originally posted by QBall
Then again, I've never gone about enabling DMA on my machine, mainly cos I don't really need it, so I may be open to correction.

You don't 'need' DMA.... what's that... like saying 'no thanks' to SCSI hard disks, or free CPU upgrades?

*ahem*.

QBall

Originally posted by Typedef
You don't 'need' DMA.... what's that... like saying 'no thanks' to SCSI hard disks, or free CPU upgrades?

*ahem*.

*ahem* yourself.

Things I do on my laptop:
Check my mail.
Browse the web.
Program.

Which one of those benefits noticeably from having DMA enabled? (Hint: None of them)

I'll get round to enabling DMA at some stage but it's not exactly high on the priority list. (Getting ACPI to work under FreeBSD and stopping Win2K freezing are though.)

Typedef

Shrug.

If you want to get decent reads from your hard disk then DMA matters.

Say you wanted to recompile your kernel, or send an email with a five megabyte attachment.

In such instances DMA matters.