Hi JM, On 23/10/24 00:48, Jean-Michel Hautbois wrote:
Hi there ! I can see there are a lot of eDMA interrupts requested at boot, on my M54418 board, but I can't see any of it used for UART while using the serial port. Is it supported in RX/TX ? Should something be done for it to be used ?
The ColdFire serial driver (drivers/tty/serial/mcf.c) does not support DMA operation. Historically very few parts had DMA support for UART block.
I am wondering, because I added a few traces (trace_printk with trace support [1]) and it seems I get one interrupt per 1 or 2 bytes only. I am using UART2 for a serial communication with another CPU, and it looks like it is using a *lot* of interrupts for the UART, and none on any eDMA interrupts ?
Even on the parts that support DMA the buffer (FIFOs) are small. On TX it is mostly a holding and shift register only, so the best you usually get is 2 bytes per TX interrupt. Some parts, like the m5441x family have a 3 byte RX FIFO, so still small. Regards Greg
