firmware/sniffer: Log parity errors, just like overruns and framing e…

…rrors

Reading of code + datasheet showed that we did enable parity checking
but never actually checked if the USART has the PARE bit in CSR set.

Let's change that.  Plus also avoid possible race conditions due to
multiple status resets via US_CR_RSTSTA.  Let's only reset that once
per interrupt handler.

TODO: actually do something useful at that point.  We currently don't
report those to the host, nor do we attempt to recover in any way.  The
data sheet also doesn't tell us what it actually does in such
situations; it appears the character is *not* returned from the USART,
so we're missing one byte in the stream at that point.

Change-Id: I5f012d86c61a2377d355396e7b95d078952bee7c
Related: OS#5464

firmware/libcommon/source/sniffer.c

@@ -800,14 +800,14 @@ void Sniffer_usart_isr(void)
  /* Read channel status register */
  uint32_t csr = sniff_usart.base->US_CSR;
  /* Verify if there was an error */
- if (csr & US_CSR_OVRE) {
- TRACE_WARNING("USART overrun error\n\r");
+ if (csr & US_CSR_OVRE)
+ TRACE_ERROR("USART overrun error\n\r");
+ if (csr & US_CSR_FRAME)
+ TRACE_ERROR("USART framing error\n\r");
+ if (csr & US_CSR_PARE)
+ TRACE_ERROR("USART parity error\n\r");
+ if (csr & (US_CSR_OVRE|US_CSR_FRAME|US_CSR_PARE))
  sniff_usart.base->US_CR |= US_CR_RSTSTA;
- }
- if (csr & US_CSR_FRAME) {
- TRACE_WARNING("USART framing error\n\r");
- sniff_usart.base->US_CR |= US_CR_RSTSTA;
- }
 
  /* Verify if character has been received */
  if (csr & US_CSR_RXRDY) {