On Fri, Aug 09, 2013 at 10:54:28AM -1000, Min Xu wrote:
> Hi Holger
Dear Min,
>
> Thanks for getting back to me. After analyzing the issue, I believe the
> issue is the overrun error the USART reports. The issue appear to stem
> from the fact that each byte received by the USART is handled in the
> interrupt handler, but the USB sending code locks out the interrupt for the
> entirety of its call. So I change the code in the following manner and it
> appears to solve the issue for me:
thank you for the analysis and the change! Would you like to create entire
git commits for the various things and follow the kernel coding style?
> 5) An additional function call in the main loop to detect (and output to
> debug serial) if an overrun occured
great! We have a slightly different coding style but the change itself looks
good and I would support it to be included.
> 1) Increase the small buffer to be large enough to hold 1 typical apdu:
> 270 bytes: 4 byte SIMTrace header, 4 byte command, 2 byte status, 1 byte
> instruction that appears to be repeated?? 256 bytes payload
this seems reasonable. Using git gui blame on the req_ctx.h I notice that
this has already been increased for the SIM, increasing it further can
make sense.
>
> 2) Disable USB interrupt before deciding to Continue to send stuff to USB
> until returning from function.
>
> 3) lock out interrupt ONLY when retrieving a new req_ctx to transmit to USB
>
> 4) Some additional code change to detect if a req_ctx is completely
> transmitted ..
I can't comment on these three as I have not looked into the inner workings
of the USB code yet.
I would propose we start with creating three git commits for the first three
things and then look into locking/disabling irqs.
thanks a lot
holger
