If using flow control with a high CTS the thread may be
blocked forever on the second transmit attempt due to waiting
on the txdma semaphore. The calling thread can then never
make progress and release any resources it has taken, thus
may cause a deadlock in other parts of the system.
The implementation differs in behavior from interrupt-driven
TX. It should not implicitly wait on a taken semaphore but
return immediately and let the upper layers decide on what to
do next.
If using flow control with a high CTS the thread may be
blocked forever on the second transmit attempt due to waiting
on the txdma semaphore. The calling thread can then never
make progress and release any resources it has taken, thus
may cause a deadlock in other parts of the system.
The implementation differs in behavior from interrupt-driven
TX. It should not implicitly wait on a taken semaphore but
return immediately and let the upper layers decide on what to
do next.
If using flow control with a high CTS the thread may be
blocked forever on the second transmit attempt due to waiting
on the txdma semaphore. The calling thread can then never
make progress and release any resources it has taken, thus
may cause a deadlock in other parts of the system.
The implementation differs in behavior from interrupt-driven
TX. It should not implicitly wait on a taken semaphore but
return immediately and let the upper layers decide on what to
do next.
If using flow control with a high CTS the thread may be blocked forever
on the second transmit attempt due to waiting on the txdma semaphore.
The calling thread can then never make progress and release any
resources it has taken, thus may cause a deadlock in other parts of the
system.
The implementation differs in behavior from interrupt-driven TX and the
STM32F7 TXDMA . It should not implicitly wait on a taken semaphore but
return immediately and let the upper layers decide on what to do next.
Some APIs are implemented both in common code and CHIP-specific code,
and the link needs to be based on the implementation in CHIP, so move
NUTTX_CHIP_ABS_DIR before common src.
Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>
These flags are not used in the code.
SERIAL_HAVE_RXDMA and SERIAL_HAVE_TXDMA flags are used instead.
STM32_UART_TXDMA flag is not even defined in Kconfig
With TCD set to loop, there is a window where the
DMA has raised Done, but not reloaded the TCD, resetting
count and clearing Done.
In this window imxrt_dmach_getcount could then return 0.
Resulting in imxrt_dma_nextrx returning RXDMA_BUFFER_SIZE.
Which is not a valid index in the FIFO.
Since the count will be set to RXDMA_BUFFER_SIZE. When the DMA
engine completes the TCD reload. The imxrt_dma_nextrx would
return 0. Therefore:
(RXDMA_BUFFER_SIZE - dmaresidual) % RXDMA_BUFFER_SIZE
accomplishes this.
With TCD set to loop, there is a window where the
DMA has raised Done, but not reloaded the TCD, resetting
count and clearing Done.
In this window imxrt_dmach_getcount could then return 0.
Resulting in imxrt_dma_nextrx returning RXDMA_BUFFER_SIZE.
Which is not a valid index in the FIFO.
Since the count will be set to RXDMA_BUFFER_SIZE. When the DMA
engine completes the TCD reload. The imxrt_dma_nextrx would
return 0. Therefore:
(RXDMA_BUFFER_SIZE - dmaresidual) % RXDMA_BUFFER_SIZE
accomplishes this.
With TCD set to loop, there is a window where the
DMA has raised Done, but not reloaded the TCD, resetting
count and clearing Done.
In this window imxrt_dmach_getcount could then return 0.
Resulting in imxrt_dma_nextrx returning RXDMA_BUFFER_SIZE.
Which is not a valid index in the FIFO.
Since the count will be set to RXDMA_BUFFER_SIZE. When the DMA
engine completes the TCD reload. The imxrt_dma_nextrx would
return 0. Therefore:
(RXDMA_BUFFER_SIZE - dmaresidual) % RXDMA_BUFFER_SIZE
accomplishes this.
With DMA enabled on some I2C channels but not all
the Non DMA channels were failing.
The cause was condition the status with only the enabled
interrupts on non DMA chennels. This conditioning needs
to only happen in DMA enabled channels
With DMA enabled on some I2C channels but not all
the Non DMA channels were failing.
The cause was condition the status with only the enabled
interrupts on non DMA chennels. This conditioning needs
to only happen in DMA enabled channels
With DMA enabled on some I2C channels but not all
the Non DMA channels were failing.
The cause was condition the status with only the enabled
interrupts on non DMA chennels. This conditioning needs
to only happen in DMA enabled channels
The DMA can bring in more rx data, than the number of
DMA completions call backs. The call back happen on
idle, 1/2 and full events. But in between these events
the DMA can write more data to the buffers memory that
need to be brought in to the cache. (invalidate)
We do the invalidate on the reads from the fifo memory
if the the DMA as commited since the last read.
