[Qemu-devel] [PATCH] uhci: Change default transaction lifetime to 32 frames

[Qemu-devel] [PATCH] uhci: Change default transaction lifetime to 32 frames

[Max Krasnyansky]

Transaction lifetime was originally set to 10 frames. That was an arbitrary
number I picked without much thinking :).
I'm changing that to 32 frames because things like interrupt transfers
and such are scheduled at that rate. It seems like 1/32 is accepted as
lowest supported rate. OHCI, for example, defines exactly 32 interrupt
heads.

While testing USB webcam under XP I noticed that interrupt transactions were
being canceled and then resubmitted on a regular basis, which works but is a
waste of CPU cycles. This change fixes that.
All other devices I have are not affected.

Signed-off-by: Max Krasnyansky <maxk@kernel.org>
---
 hw/usb-uhci.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/hw/usb-uhci.c b/hw/usb-uhci.c
index 62c743d..b90cf78 100644
--- a/hw/usb-uhci.c
+++ b/hw/usb-uhci.c
@@ -781,7 +781,7 @@ static int uhci_handle_td(UHCIState *s, uint32_t addr, UHCI_TD *td, uint32_t *in
     async = uhci_async_find_td(s, addr, td->token);
     if (async) {
         /* Already submitted */
-        async->valid = 10;
+        async->valid = 32;
 
         if (!async->done)
             return 1;
-- 
1.5.5.1

[Qemu-devel] Re: [PATCH] uhci: Change default transaction lifetime to 32 frames

[Anthony Liguori]

Max Krasnyansky wrote:
> Transaction lifetime was originally set to 10 frames. That was an arbitrary
> number I picked without much thinking :).
> I'm changing that to 32 frames because things like interrupt transfers
> and such are scheduled at that rate. It seems like 1/32 is accepted as
> lowest supported rate. OHCI, for example, defines exactly 32 interrupt
> heads.
>
> While testing USB webcam under XP I noticed that interrupt transactions were
> being canceled and then resubmitted on a regular basis, which works but is a
> waste of CPU cycles. This change fixes that.
> All other devices I have are not affected.
>   

Applied.  Thanks.

Regards,

Anthony Liguori

> Signed-off-by: Max Krasnyansky <maxk@kernel.org>
> ---
>  hw/usb-uhci.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/hw/usb-uhci.c b/hw/usb-uhci.c
> index 62c743d..b90cf78 100644
> --- a/hw/usb-uhci.c
> +++ b/hw/usb-uhci.c
> @@ -781,7 +781,7 @@ static int uhci_handle_td(UHCIState *s, uint32_t addr, UHCI_TD *td, uint32_t *in
>      async = uhci_async_find_td(s, addr, td->token);
>      if (async) {
>          /* Already submitted */
> -        async->valid = 10;
> +        async->valid = 32;
>  
>          if (!async->done)
>              return 1;
>