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stm32: lowputc: Ensure USART is disabled before configuring

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arch/arm/src/stm32/stm32_lowputc.c:

    * stm32_lowsetup(): Ensure the USART is disabled before attempting
      to configure it because some register bits cannot be modified
      otherwise. This solves an issue that was encountered when a
      serial bootloader did not perform a full teardown/cleanup before
      launching NuttX.
This commit is contained in:
Nathan Hartman
2020-09-04 17:33:06 -04:00
committed by David Sidrane
parent b88038a1e1
commit e67f72b02d
1 changed files with 12 additions and 0 deletions
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arch/arm/src/stm32/stm32_lowputc.c
+12
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@@ -614,6 +614,18 @@ void stm32_lowsetup(void)
/* Enable and configure the selected console device */
#if defined(HAVE_CONSOLE) && !defined(CONFIG_SUPPRESS_UART_CONFIG)
/* Ensure the USART is disabled because some bits of the following
* registers cannot be modified otherwise.
*
* Although the USART is expected to be disabled at power on reset, this
* might not be the case if we boot from a serial bootloader that does not
* clean up properly.
*/
cr = getreg32(STM32_CONSOLE_BASE + STM32_USART_CR1_OFFSET);
cr &= ~USART_CR1_UE;
putreg32(cr, STM32_CONSOLE_BASE + STM32_USART_CR1_OFFSET);
/* Configure CR2 */
cr = getreg32(STM32_CONSOLE_BASE + STM32_USART_CR2_OFFSET);