serial: stm32: fix TX and RX FIFO thresholds

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[ Upstream commit 25a8e7611d ]

TX and RX FIFO thresholds may be cleared after suspend/resume, depending
on the low power mode.

Those configurations (done in startup) are not effective for UART console,
as:
- the reference manual indicates that FIFOEN bit can only be written when
  the USART is disabled (UE=0)
- a set_termios (where UE is set) is requested firstly for console
  enabling, before the startup.

Fixes: 84872dc448 ("serial: stm32: add RX and TX FIFO flush")
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210304162308.8984-5-erwan.leray@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

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Erwan Le Ray 2021-03-04 17:22:59 +01:00 • committed by Greg Kroah-Hartman

parent 5ca0d5b2c8

commit 69ac7b3b89

1 changed files with 9 additions and 14 deletions

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drivers/tty/serial/stm32-usart.c

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