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serial: uart_nrfx_uarte: graceful async power down

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Gracefully shutdown the UARTE peripheral when the async API is used.
Failure to do so results in the driver being unusable when powered back
up as the required events (ENDTX & TXSTOPPED) are not set. This also
ensures that the last byte sent out via `poll_out` is properly output
on the serial line before powering down.

Fixes #31930.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>
This commit is contained in:
Jordan Yates 2021-02-04 21:41:10 +10:00 • committed by Anas Nashif
commit 238067dfc1
1 changed files with 38 additions and 16 deletions
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54
drivers/serial/uart_nrfx_uarte.c
View file

@ -424,6 +424,33 @@ static bool is_tx_ready(const struct device *dev)
nrf_uarte_event_check(uarte, NRF_UARTE_EVENT_ENDTX) : 0);
}
/* Wait until the transmitter is in the idle state. When this function returns,
* IRQ's are locked with the returned key.
*/
static int wait_tx_ready(const struct device *dev)
{
int key;
do {
/* wait arbitrary time before back off. */
bool res;
NRFX_WAIT_FOR(is_tx_ready(dev), 100, 1, res);
if (res) {
key = irq_lock();
if (is_tx_ready(dev)) {
break;
}
irq_unlock(key);
}
k_msleep(1);
} while (1);
return key;
}
static void tx_start(NRF_UARTE_Type *uarte, const uint8_t *buf, size_t len)
{
nrf_uarte_tx_buffer_set(uarte, buf, len);
@ -1148,22 +1175,7 @@ static void uarte_nrfx_poll_out(const struct device *dev, unsigned char c)
irq_unlock(key);
}
} else {
do {
/* wait arbitrary time before back off. */
bool res;
NRFX_WAIT_FOR(is_tx_ready(dev), 100, 1, res);
if (res) {
key = irq_lock();
if (is_tx_ready(dev)) {
break;
}
irq_unlock(key);
}
k_msleep(1);
} while (1);
key = wait_tx_ready(dev);
}
/* At this point we should have irq locked and any previous transfer
@ -1587,6 +1599,16 @@ static void uarte_nrfx_set_power_state(const struct device *dev,
data->async->rx_total_user_byte_cnt = 0;
}
if (get_dev_data(dev)->async) {
/* Wait for the transmitter to go idle.
* While the async API can wait for transmission to
* complete before disabling the peripheral, the poll
* API exits before the character is sent on the wire.
* If the transmission is ongoing when the peripheral
* is disabled, the ENDTX and TXSTOPPED events will
* never be generated. This will block the driver in
* any future calls to poll_out.
*/
irq_unlock(wait_tx_ready(dev));
nrf_uarte_disable(uarte);
uarte_nrfx_pins_enable(dev, false);
return;