When the Head to Tail relationship was H < T, then
only the tail to end of buffer was sent.
The fix is: In the txdma completion to do a second
the DMA operation using nbuffer if the nlength is
non zero.
stm32f7:serial UART5 use actual size
UART5 was using the CONFIG_UART5_TXBUFSIZE
not the UART5_TXBUFSIZE_ADJUSTED.
Since the buffer size was adjusted up, this
has no dcache implications.
If the UART5_TXBUFSIZE_ADJUSTED is larger
then CONFIG_UART5_TXBUFSIZE it will present
a larger usable buffer to the system's
serial driver.
4a6f7cacd5