UP xtreme SPI speed problem
i have upboard with RT-patch is being used for SPI communication. (more than 6MHz)
(ubuntu16.04, kernel 4.4.86)
link : https://github.com/QiayuanLiao/Ubuntu-RT-UP-Board
recently, I needed a faster operation, so I bought up extreme.
(ubuntu18.04, kernel Linux upxtreme-UP-WHL01 5.0.0-1-generic)
link : https://wiki.up-community.org/Ubuntu_18.04#Install_Ubuntu_kernel_5.0.0_from_PPA_on_Ubuntu_18.04
i expected batter than UPboard. but I can currently communicate with SPI at a speed of 2MHz.
When the communication speed is increased(more than 2MHz), data corruption or shift occur.
I tried applying lowlatency as well, but it failed(same problem).
The development board(STM32F4) is directly connected on the 40pin header, and there is no communication problem in the upboard.
data length is more than 100byte.
spi mode : SPI_MODE_0
bits per word : 8bits
SPI_IOC_RD_LSB_FIRST : 0x01