Re: [Qemu-devel] [PATCH] ide: fix DMA register transitions

[John Snow <jsnow@redhat.com>]

On 08/02/2016 06:05 PM, John Snow wrote:
> ATA8-APT defines the state transitions for both a host controller and
> for the hardware device during the lifecycle of a DMA transfer, in
> section 9.7 "DMA command protocol."
>
> One of the interesting tidbits here is that when a device transitions
> from DDMA0 ("Prepare state") to DDMA1 ("Data_Transfer State"), it can
> choose to set either BSY or DRQ to signal this transition, but not both.
>
> as ide_sector_dma_start is the last point in our preparation process
> before we begin the real data transfer process (for either AHCI or BMDMA),
> this is the correct transition point for DDMA0 to DDMA1.
>
> I have chosen !BSY && DRQ for QEMU to make the transition from DDMA0 the
> most obvious.
>
> Reported-by: Benjamin David Lunt <fys@fysnet.net>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  hw/ide/core.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/ide/core.c b/hw/ide/core.c
> index d117b7c..e961d42 100644
> --- a/hw/ide/core.c
> +++ b/hw/ide/core.c
> @@ -907,7 +907,7 @@ eot:
>
>  static void ide_sector_start_dma(IDEState *s, enum ide_dma_cmd dma_cmd)
>  {
> -    s->status = READY_STAT | SEEK_STAT | DRQ_STAT | BUSY_STAT;
> +    s->status = READY_STAT | SEEK_STAT | DRQ_STAT;
>      s->io_buffer_size = 0;
>      s->dma_cmd = dma_cmd;
>
>

Thanks, applied to my IDE-Next tree:

https://github.com/jnsnow/qemu/commits/ide-next
https://github.com/jnsnow/qemu.git

--js