Re: [Qemu-devel] enabling bus-master IDE driver

[Jens Axboe]

On Sun, Nov 07 2004, Jens Axboe wrote:
> On Sat, Nov 06 2004, Jason Brittain wrote:
> > Johannes Schindelin wrote:
> > >Hi,
> > >
> > >On Fri, 5 Nov 2004, Jason Brittain wrote:
> > >
> > >
> > >>/dev/hda:
> > >> setting using_dma to 1 (on)
> > >> HDIO_SET_DMA failed: Operation not permitted
> > >> using_dma    =  0 (off)
> > >
> > >Are you sure you did as guest root? This error could happen if you try to
> > >use hdparm as a plain user. 
> > 
> > I was most certainly logged in as root in the guest Linux
> > when I did that.
> 
> I has nothing to do with user privilege, you are most likely getting
> EPERM because the drive doesn't flag dma capability.
> 
>     put_le16(p + 49, 1 << 9); /* LBA supported, no DMA */
> 
> mask that with 1 << 8 and it'll most likely work.
> 
> Index: hw/ide.c
> ===================================================================
> RCS file: /cvsroot/qemu/qemu/hw/ide.c,v
> retrieving revision 1.28
> diff -u -r1.28 ide.c
> --- hw/ide.c  9 Oct 2004 20:27:55 -0000       1.28
> +++ hw/ide.c  7 Nov 2004 09:06:33 -0000
> @@ -416,7 +416,7 @@
>      put_le16(p + 47, 0x8000 | MAX_MULT_SECTORS);
>  #endif
>      put_le16(p + 48, 1); /* dword I/O */
> -    put_le16(p + 49, 1 << 9); /* LBA supported, no DMA */
> +    put_le16(p + 49, 1 << 9 | 1 << 8); /* DMA and LBA supported */
>      put_le16(p + 51, 0x200); /* PIO transfer cycle */
>      put_le16(p + 52, 0x200); /* DMA transfer cycle */
>      put_le16(p + 53, 1); /* words 54-58 are valid */

Did a quick test on a rescue iso boot, works for me. hdparm -t went from
55MiB/sec in pio to 100MiB/sec with sdma2.

-- 
Jens Axboe