serial: stm32: replace access to DMAR bit by dmaengine_pause/resume

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It's rather advised to rely on DMA pause / resume instead of
clearing/setting DMA request enable bit for the same purpose. Some DMA
request/acknowledge race may encountered by doing so. We prefer to use
dmaengine_pause and resume instead to pause a dma transfer when it is
necessary.

Create two new functions (stm32_usart_rx_dma_pause, stm32_usart_rx_dma
_resume) to handle dma error when pausing/resuming.

And rename stm32_usart_start_rx_dma_cyclic() to
stm32_usart_rx_dma_start_or_resume() and use this function to resume an
rx dma transfer. If resume fail, stm32_usart_rx_dma_start_or_resume can
create a new transfer to continue.

It is also safer to close DMA before reset DMAR in stm32_usart_shutdown.

Signed-off-by: Valentin Caron <valentin.caron@foss.st.com>
Link: https://lore.kernel.org/r/20230808161906.178996-6-valentin.caron@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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Valentin Caron 2023-08-08 18:19:05 +02:00 • committed by Greg Kroah-Hartman

parent 7f28bcea82

commit a01ae50d7e

1 changed files with 106 additions and 94 deletions

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drivers/tty/serial/stm32-usart.c

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