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Fix uart race condition dropping bytes on NRF52 

In nordic_nrf5_uart_event_handler if the events NRF_UARTE_EVENT_ENDRX
and NRF_UARTE_EVENT_RXSTARTED become pending after the check for
NRF_UARTE_EVENT_ENDRX but before the check for
NRF_UARTE_EVENT_RXSTARTED the RX DMA buffers will be setup incorrectly
by nordic_nrf5_uart_event_handler_rxstarted because active_bank hasn't
been updated. This cause dropped and incorrect data.

This patch fixes that problem by adding a second check for
NRF_UARTE_EVENT_ENDRX after checking for NRF_UARTE_EVENT_RXSTARTED
and skipping processing if NRF_UARTE_EVENT_ENDRX is set. The
subsequent interrupt will process both in the correct order. This
ensures that these events cannot be handled out of order and thus fixes
the corruption.
pull/8784/head
Russ Butler 2018-11-16 17:30:31 -06:00
parent d643034941
commit 4cda158e55
1 changed files with 8 additions and 2 deletions
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10
targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/serial_api.c
View File

@ -727,8 +727,14 @@ static void nordic_nrf5_uart_event_handler(int instance)
}
}
/* Rx DMA buffer has been armed. */
if (nrf_uarte_event_check(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_RXSTARTED))
/* Rx DMA buffer has been armed.
*
* Warning - Do not process NRF_UARTE_EVENT_RXSTARTED if NRF_UARTE_EVENT_ENDRX is pending.
* NRF_UARTE_EVENT_RXSTARTED must be processed first or nordic_nrf5_uart_event_handler_rxstarted
* will setup the wrong DMA buffer and cause data to be lost.
*/
if (nrf_uarte_event_check(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_RXSTARTED) &&
!nrf_uarte_event_check(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_ENDRX))
{
nrf_uarte_event_clear(nordic_nrf5_uart_register[instance], NRF_UARTE_EVENT_RXSTARTED);