From 7f1a560288a09ffc559f8571e3568b3cc10b28d2 Mon Sep 17 00:00:00 2001
From: Uwe Bonnes <bon@elektron.ikp.physik.tu-darmstadt.de>
Date: Tue, 11 May 2021 11:21:27 +0200
Subject: [PATCH] stm32/usbuart: Clear USART_ICR if provided.

Otherwise endless interrupts happened.
---
 src/platforms/stm32/usbuart.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/platforms/stm32/usbuart.c b/src/platforms/stm32/usbuart.c
index 4775e1d3..8c04db7b 100644
--- a/src/platforms/stm32/usbuart.c
+++ b/src/platforms/stm32/usbuart.c
@@ -399,8 +399,15 @@ void USBUSART_ISR(void)
 	usart_recv(USBUSART);
 
 	/* If line is now idle, then transmit a packet */
-	if (isIdle)
+	if (isIdle) {
+#if defined(USART_ICR)
+		USART_ICR(USBUSART) = USART_ICR_IDLECF;
+#else
+		/* On the older uarts, the sequence "read flags", "read DR"
+		 * as above cleared the flags */
+#endif
 		usbuart_run();
+	}
 
 	nvic_enable_irq(USBUSART_DMA_RX_IRQ);
 }