danielappiagyei-bc commented on code in PR #11020:
URL: https://github.com/apache/nuttx/pull/11020#discussion_r1373486112
##########
arch/arm/src/imxrt/imxrt_serial.c:
##########
@@ -1373,6 +1373,7 @@ static inline void imxrt_serialout(struct imxrt_uart_s
*priv,
static int imxrt_dma_nextrx(struct imxrt_uart_s *priv)
{
int dmaresidual = imxrt_dmach_getcount(priv->rxdma);
+ DEBUGASSERT(dmaresidual <= RXDMA_BUFFER_SIZE);
Review Comment:
Appreciate the thorough work here david. I don't have an answer for why I'm
experiencing the issue while you're not. I apologize for not having a branch
with a minimum, reproducible example to give you, as I'm using my company's
codebase as a test bed. Are you opposed to me just making a PR with my
suggested fix? It is only an extra `if` statement with a simple conditional so
performance really shouldn't be affected. It also does not make the existing
code suddenly incorrect, so I don't see any negatives to it
```
static unsigned int imxrt_dma_nextrx(struct imxrt_uart_s *priv)
{
unsigned int dmaresidual = imxrt_dmach_getcount(priv->rxdma);
DEBUGASSERT(dmaresidual <= RXDMA_BUFFER_SIZE);
if (dmaresidual == 0)
{
/* We've finished transferring RXDMA_BUFFER_SIZE bytes. The next byte
* will be placed at the beginning of the buffer
*/
return 0;
}
else
{
return RXDMA_BUFFER_SIZE - dmaresidual;
}
}
```
This is essentially equivalent to what you did for `kinetis_serial.c`:
```
return (RXDMA_BUFFER_SIZE - (int)dmaresidual) % RXDMA_BUFFER_SIZE;
```
Note that `kinetis_edma.c` [also has a EDMA_TCD_DONE
flag](https://github.com/apache/nuttx/blob/master/arch/arm/src/kinetis/kinetis_edma.c#L1051)
The register description of the eDMA `DONE` flag I posted earlier does not
say that it won't automatically be set for our configuration. I can post on the
NXP support forum and ask them specifically about the IMXRT1064 and place the
reply here.
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