I have a RSB4210 board (i.MX536) from Advantech running Linux 220.127.116.11.
I am reading data from UART5 at 460800 bit/s.
I have issues similar to those described at https://community.freescale.com/thread/357233
I can't just take latest freescale 18.104.22.168 kernel from git because it requires some RSB4210-specific changes.
So I have disabled DMA - set #define UART5_DMA_ENABLE 0 at arch/arm/mach-mx5/serial.h.
This improved the result, but the problem remains:
I constantly read data from UART5, but sometimes overruns occur and data gets corrupted.
This happens few times a second but if CPU load increases it happens more frequently.
Overrun counter "oe:" keeps increasing in /proc/tty/driver/ttymxc.
I looked into drivers/serial/mxc_uart.c and found the following detail.
mxcuart_int() does all work and is called constantly with 100-200 microsecond intervals (depending on UART5_UFCR_RXTL threshold).
But sometimes next mxcuart_int() call happens in 5 milliseconds after its previous call.
In this situation driver detects overrun and increases "oe" counter.
I have turned off Ethernet but overruns still occur.
What can periodically delay mxcuart_int() call for 5 milliseconds?
Eliminating that could probably fix my issue.