serial: stm32: Reset .throttled state in .startup()

Uwe Kleine-König · gregkh · commit ea2624b5b829 · 2024-04-17T13:26:45.000+02:00
When an UART is opened that still has .throttled set from a previous open, the RX interrupt is enabled but the irq handler doesn't consider it. This easily results in a stuck irq with the effect to occupy the CPU in a tight loop. So reset the throttle state in .startup() to ensure that RX irqs are handled. Fixes: d1ec8a2 ("serial: stm32: update throttle and unthrottle ops for dma mode") Cc: stable@vger.kernel.org Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> Link: https://lore.kernel.org/r/a784f80d3414f7db723b2ec66efc56e1ad666cbf.1713344161.git.u.kleine-koenig@pengutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
@@ -1092,6 +1092,7 @@ static int stm32_usart_startup(struct uart_port *port)
 		val |= USART_CR2_SWAP;
 		writel_relaxed(val, port->membase + ofs->cr2);
 	}
+	stm32_port->throttled = false;
 
 	/* RX FIFO Flush */
 	if (ofs->rqr != UNDEF_REG)

Original file line number	Diff line number	Diff line change
`@@ -1092,6 +1092,7 @@ static int stm32_usart_startup(struct uart_port *port)`
`1092`	`1092`	`val \|= USART_CR2_SWAP;`
`1093`	`1093`	`writel_relaxed(val, port->membase + ofs->cr2);`
`1094`	`1094`	`}`
	`1095`	`+ stm32_port->throttled = false;`
`1095`	`1096`
`1096`	`1097`	`/* RX FIFO Flush */`
`1097`	`1098`	`if (ofs->rqr != UNDEF_REG)`