Re: [Qemu-devel] [PULL 1/6] audio/hda: create millisecond timers that handle IO

[Max Reitz <mreitz@redhat.com>]

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On 2018-06-25 15:12, Gerd Hoffmann wrote:
> Currently, the HDA device tries to sync itself with the QEMU audio
> backend by waiting for the guest driver to handle buffer completion
> interrupts. This causes the backend to often read too much data from the
> device, as well as running out of data whenever the guest takes too long
> to handle the interrupt.
> 
> According to the HDA specification, the guest is also not required to
> use interrupts, but can also sync itself by polling the LPIB registers.
> 
> This patch will introduce high frequency (1000Hz) timers that interface
> with the device and allow for much smoother emulation of the LPIB
> registers. Since the timing is now provided by these timers, the need
> to wait for buffer completion interrupts also ceases.
> 
> Signed-off-by: Martin Schrodt <martin@schrodt.org>
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> Message-id: 20180622111200.30561-2-kraxel@redhat.com
> Message-id: 20171015184033.2951-3-martin@schrodt.org
> 
> [ kraxel: keep old code for compatibility with older qemu versions,
>           add property to switch code paths at runtime ]
> [ kraxel: new code is disabled by default, use-timer=on enables it ]
> 
> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  hw/audio/hda-codec.c | 263 ++++++++++++++++++++++++++++++++++++++++++++++-----
>  hw/audio/intel-hda.c |   7 --
>  2 files changed, 237 insertions(+), 33 deletions(-)

This patch breaks compilation on clang with -m32 for me, because I
apparently I don't have 64 bit atomics there.  Should there be
CONFIG_ATOMIC64 guards and handling for when that isn't defined?

Max


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