FLEXSPI IP request with eDMA sometimes returns "grant timeout error"

[aleksejshch]

Hi! I have an issue with FLEXSPI2. Board - MIMXRT1160-EVK; SDK 2.14 for GCC.

I use FLXSPI for communication with FPGA, QSPI mode. I implemented IP requests based on example flexspi_nor_edma_transfer. There are 2 functions: write 128-bytes block, and read 128-bytes block. And sometimes I can see on logic analyzer' captures that TX transaction breaks: I can see just part of transmitted data (48 or 64 bytes another number), and CS gets stuck at "0", but I receive DMA transaction complete event in DMA callback.

I added also interrupt handler to check errors from FLEXSPI, and I can see that I receive also "grant timeout event" (bit IPCMDGE in INTR reg).

My project is based on FreeRTOS. I have also working 1G ethernet, USB host, and configured SDRAM. I use default configurations for FLEXSPI and eDMA (use EDMA_GetDefaultConfig() and FLEXSPI_GetDefaultConfig()). I checked this issue also with code execution from ITCM, and it repeats.

I tried to increase/decrease rxWatermark / txWatermark, but it didn't make a difference.

I can't find any cause of this effect, or don't know how to handle it properly.

Also I can see another issue with FLEXSPI when I start to copy big buffers with DMA mem-to-mem (another DMA channel) in another task, where I configured lower interrupt priority. And sometimes I can see "stucking" of FLEXSPI TX transaction: with logic analyzer I can see sent command code, then long delay (~10 ms), and then data from buffer starts to transmit. It looks like latency: DMA ch "0" which handles FLEXSPI TX "waiting" for complete of DMA ch "2" (mem-to-mem, from/to external onboard SDRAM).

I can't find any Application Note about eDMA, and in Reference Manual I can't find number of eDMA engines or channel priorities.

Is it possible to configure highest priority for FLEXSPI' DMA channel? 

I also attached QSPI captures for DSView with both of issues, you can see at the end of capture.

Thanks.

[Kan_Li]

Hi @aleksejshch ,

Maybe the modules like 1G ethernet and USB host used in your application also put their buffers in the SDRAM, so lead to such kind of issue, my suggestion would be put the spaces used for above modules as non-cacheable memory , you may refer to https://www.nxp.com.cn/docs/en/application-note/AN12042.pdf for details.

Have a great day,
Kan

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