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drivers: serial: pl011: prevent concurrent interrupt callback execution

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Since the callback can be executed from either software or a hardware
interrupt, it's possible for multiple instances of the callback function
to run concurrently. That should not happen and can be particularly
problematic on SMP systems. This commit adds a spinlock to prevent
concurrent execution.

This addresses a Twister CI failure discovered in #85539.

Signed-off-by: Xudong Zheng <7pkvm5aw@slicealias.com>
This commit is contained in:
Xudong Zheng 2025-02-15 17:00:40 -05:00 committed by Benjamin Cabé
parent 784f5b5bbd
commit e885c8c42f
1 changed files with 33 additions and 20 deletions
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53
drivers/serial/uart_pl011.c
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@ -74,6 +74,7 @@ struct pl011_data {
#ifdef CONFIG_UART_INTERRUPT_DRIVEN
volatile bool sw_call_txdrdy;
uart_irq_callback_user_data_t irq_cb;
struct k_spinlock irq_cb_lock;
void *irq_cb_data;
#endif
};
@ -342,26 +343,36 @@ static void pl011_irq_tx_enable(const struct device *dev)
struct pl011_data *data = dev->data;
get_uart(dev)->imsc |= PL011_IMSC_TXIM;
if (data->sw_call_txdrdy) {
data->sw_call_txdrdy = false;
if (!data->sw_call_txdrdy) {
return;
}
data->sw_call_txdrdy = false;
/* Verify if the callback has been registered */
if (data->irq_cb) {
/*
* Due to HW limitation, the first TX interrupt should
* be triggered by the software.
*
* PL011 TX interrupt is based on a transition through
* a level, rather than on the level itself[1]. So that,
* enable TX interrupt can not trigger TX interrupt if
* no data was filled to TX FIFO at the beginning.
*
* [1]: PrimeCell UART (PL011) Technical Reference Manual
* functional-overview/interrupts
*/
while (get_uart(dev)->imsc & PL011_IMSC_TXIM) {
data->irq_cb(dev, data->irq_cb_data);
}
/*
* Verify if the callback has been registered. Due to HW limitation, the
* first TX interrupt should be triggered by the software.
*
* PL011 TX interrupt is based on a transition through a level, rather
* than on the level itself[1]. So that, enable TX interrupt can not
* trigger TX interrupt if no data was filled to TX FIFO at the
* beginning.
*
* [1]: PrimeCell UART (PL011) Technical Reference Manual
* functional-overview/interrupts
*/
if (!data->irq_cb) {
return;
}
/*
* Execute callback while TX interrupt remains enabled. If
* uart_fifo_fill() is called with small amounts of data, the 1/8 TX
* FIFO threshold may never be reached, and the hardware TX interrupt
* will never trigger.
*/
while (get_uart(dev)->imsc & PL011_IMSC_TXIM) {
K_SPINLOCK(&data->irq_cb_lock) {
data->irq_cb(dev, data->irq_cb_data);
}
}
}
@ -626,7 +637,9 @@ void pl011_isr(const struct device *dev)
/* Verify if the callback has been registered */
if (data->irq_cb) {
data->irq_cb(dev, data->irq_cb_data);
K_SPINLOCK(&data->irq_cb_lock) {
data->irq_cb(dev, data->irq_cb_data);
}
}
}
#endif /* CONFIG_UART_INTERRUPT_DRIVEN */