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drivers: serial: nrfx_uarte: Add workaround for FRAMETIMEOUT corner case #85392

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drivers: serial: nrfx_uarte: Add workaround for FRAMETIMEOUT corner case #85392

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47 changes: 45 additions & 2 deletions drivers/serial/uart_nrfx_uarte.c
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Original file line number Diff line number Diff line change
Expand Up @@ -95,6 +95,17 @@ LOG_MODULE_REGISTER(uart_nrfx_uarte, CONFIG_UART_LOG_LEVEL);
#define UARTE_HAS_FRAME_TIMEOUT 1
#endif

/* Frame timeout has a bug that countdown counter may not be triggered in some
* specific condition. It may happen if RX is manually started after ENDRX (STOPRX
* task was not triggered) and there is ongoing reception of a byte. RXDRDY event
* triggered by the reception of that byte may not trigger frame timeout counter.
* If this is the last byte of a transfer then without the workaround there will
* be no expected RX timeout.
*/
#ifdef UARTE_HAS_FRAME_TIMEOUT
#define RX_FRAMETIMEOUT_WORKAROUND 1
#endif

#define INSTANCE_NEEDS_CACHE_MGMT(unused, prefix, i, prop) UARTE_IS_CACHEABLE(prefix##i)

#if UARTE_FOR_EACH_INSTANCE(INSTANCE_NEEDS_CACHE_MGMT, (+), (0), _)
Expand Down Expand Up @@ -251,6 +262,8 @@ struct uarte_nrfx_data {
#define UARTE_FLAG_LOW_POWER (UARTE_FLAG_LOW_POWER_TX | UARTE_FLAG_LOW_POWER_RX)
#define UARTE_FLAG_TRIG_RXTO BIT(2)
#define UARTE_FLAG_POLL_OUT BIT(3)
/* Flag indicating that a workaround for not working frame timeout is active. */
#define UARTE_FLAG_FTIMEOUT_WATCH BIT(4)

/* If enabled then ENDTX is PPI'ed to TXSTOP */
#define UARTE_CFG_FLAG_PPI_ENDTX BIT(0)
Expand Down Expand Up @@ -1304,9 +1317,22 @@ static void rx_timeout(struct k_timer *timer)
NRF_UARTE_Type *uarte = get_uarte_instance(dev);

#ifdef UARTE_HAS_FRAME_TIMEOUT
if (!nrf_uarte_event_check(uarte, NRF_UARTE_EVENT_RXDRDY)) {
nrf_uarte_task_trigger(uarte, NRF_UARTE_TASK_STOPRX);
struct uarte_nrfx_data *data = dev->data;
struct uarte_async_rx *async_rx = &data->async->rx;
bool rxdrdy = nrf_uarte_event_check(uarte, NRF_UARTE_EVENT_RXDRDY);

if (IS_ENABLED(RX_FRAMETIMEOUT_WORKAROUND) &&
(atomic_and(&data->flags, ~UARTE_FLAG_FTIMEOUT_WATCH) & UARTE_FLAG_FTIMEOUT_WATCH)) {
if (rxdrdy) {
nrf_uarte_event_clear(uarte, NRF_UARTE_EVENT_RXDRDY);
k_timer_start(&async_rx->timer, async_rx->timeout, K_NO_WAIT);
}
} else {
if (!rxdrdy) {
nrf_uarte_task_trigger(uarte, NRF_UARTE_TASK_STOPRX);
}
}

return;
#else /* UARTE_HAS_FRAME_TIMEOUT */
struct uarte_nrfx_data *data = dev->data;
Expand Down Expand Up @@ -1532,6 +1558,7 @@ static void endrx_isr(const struct device *dev)
async_rx->offset = 0;

if (async_rx->enabled) {
bool start_timeout = false;
/* If there is a next buffer, then STARTRX will have already been
* invoked by the short (the next buffer will be filling up already)
* and here we just do the swap of which buffer the driver is following,
Expand All @@ -1546,6 +1573,11 @@ static void endrx_isr(const struct device *dev)
*/
if (!nrf_uarte_event_check(uarte, NRF_UARTE_EVENT_RXSTARTED)) {
nrf_uarte_task_trigger(uarte, NRF_UARTE_TASK_STARTRX);
nrf_uarte_event_clear(uarte, NRF_UARTE_EVENT_RXTO);
if (IS_ENABLED(RX_FRAMETIMEOUT_WORKAROUND)) {
data->flags |= UARTE_FLAG_FTIMEOUT_WATCH;
start_timeout = true;
}
}
/* Remove the short until the subsequent next buffer is setup */
nrf_uarte_shorts_disable(uarte, NRF_UARTE_SHORT_ENDRX_STARTRX);
Expand All @@ -1554,6 +1586,11 @@ static void endrx_isr(const struct device *dev)
}

irq_unlock(key);
if (IS_ENABLED(UARTE_HAS_FRAME_TIMEOUT)) {
if (start_timeout && !K_TIMEOUT_EQ(async_rx->timeout, K_NO_WAIT)) {
k_timer_start(&async_rx->timer, async_rx->timeout, K_NO_WAIT);
}
}
}

#if !defined(CONFIG_UART_NRFX_UARTE_ENHANCED_RX)
Expand Down Expand Up @@ -1611,6 +1648,12 @@ static void rxto_isr(const struct device *dev)
struct uarte_nrfx_data *data = dev->data;
struct uarte_async_rx *async_rx = &data->async->rx;

if (IS_ENABLED(RX_FRAMETIMEOUT_WORKAROUND)) {
if (atomic_test_and_clear_bit(&data->flags, UARTE_FLAG_FTIMEOUT_WATCH)) {
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@anangl anangl Mar 20, 2025 •
edited
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Suggested change
if (atomic_test_and_clear_bit(&data->flags, UARTE_FLAG_FTIMEOUT_WATCH)) {
if (atomic_test_and_clear_bit(&data->flags, UARTE_FLAG_FTIMEOUT_WATCH_BIT)) {

But perhaps it would be better, for consistency with other flags, to not use UARTE_FLAG_FTIMEOUT_WATCH_BIT at all, just UARTE_FLAG_FTIMEOUT_WATCH and atomic_and().

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done

k_timer_stop(&async_rx->timer);
}
}

if (async_rx->buf) {
#ifdef CONFIG_HAS_NORDIC_DMM
(void)dmm_buffer_in_release(config->mem_reg, async_rx->usr_buf, 0, async_rx->buf);
Expand Down
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