FC3: DVD DMA support vs libata, a (S)ATA(PI) nightmare?

[Robin Laing]

wwp wrote:
> Hello all!
> 
> 
> I'm unsuccessfully struggling w/ DMA support for my Dell D810's DVD drive
> (`hdparm -d 1 /dev/hdc` fails, and I get poor performances when
> reading/writing, it even slows down the reactivity of the system).
> 
> I'm running out of ideas and even of hope, since none of my attempts to get
> DMA were successful, and reading/writing CD/DVD w/ such prehistoric perfs :-).
> 
> I tried to customize/rebuild a 2.6.12-1.1381_FC3 kernel to get the following
> lines in include/linux/libata.h:
>   #define ATA_ENABLE_ATAPI
>   #define ATA_ENABLE_PATA
> then tried hdc=ide-scsi or hdc=scsi as boot params, loading ide-scsi module
> thru /etc/rc.local, but nothing works. According to the variety of tests I
> did, I get or not /dev/hdc, /dev/scd0 or /dev/sr0 (if I add the device node
> manually), w/ various hdparm reports (read-ahead info present or not) but
> hdparm always fails to set DMA:
> 
> /dev/(hdc|sr0|scd0):
>  setting using_dma to 1 (on)
>  HDIO_SET_DMA failed: Invalid argument
> 
> FYI, w/ default boot params of FC3 kernel, I get:
> /dev/sda <- the hdd
> /dev/hdc <- the CD/DVD drive (CD recorder)
> 
> If I use hdc=ide-scsi, /var/log/messages tells me:
>   kernel: sr0: scsi3-mmc drive: 8x/24x writer cd/rw xa/form2 cdda tray
> but I'm not that confident that ide-scsi should be used
> since /var/log/messages tells me:
>   ide-scsi is deprecated for cd burning! Use ide-cd and give dev=/dev/hdX as device
> 
> Any hint would be welcome, I'm definitely lost now! :-) Can't FC3 kernels
> (even if modified) enable DMA for such DVD drives? Should I use a vanilla
> kernel? How to use ide-cd? Is there life on Mars, and hope for me?
> 
> BTW: noticed that `modprobe -r ide-scsi` simply crashes the kernel, huhu.
> 
> 
> References:
> http://cri.ch/linux/docs/sk0010.html
> http://www.lazy8.nu/delld180/DebianLinuxOnDellLattitude810laptop.html
> http://casa.colorado.edu/~ajsh/alienware/index.html#DVD
> http://tkrat.org/d810/
> http://fedora.redhat.com/docs/release-notes/fc3/x86/
> 
> 
> Regards,
> 

I have a similar issue with FC4 and my Toshiba Laptop.  In my case it 
is related to the controller IH6 if I remember off of the top of my 
head.  As it has been in heavy usage, I have not been able to look 
into it much.

 From what I do remember is it has to do with two different driver 
types and this has to be re-written into one single driver.  It may 
not be your problem.