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Native CS in imx6ul

Question asked by Surendra Dhobale on Jan 31, 2018
Latest reply on Jan 31, 2018 by igorpadykov


           We have interfaced imx6ul with max310x ( max14830) uart expander over spi. As we require multiple UART ports, connected four uart expander chip on each ecSPI bus (ecspi1,ecspi2,ecspi3,ecspi4).
Currently using one interface -ecspi1, Interfaces is working when gpio chip select is used as chip select source. But the reading of the data is slower and loss of data with 115200 baudrate when simultaneously send the data over two ports of the expander chip.

Planned  to use the native chip select. Instead of the gpio used dedicated chip select, in dts configuration.

We can observed the chip select become active to each clock cycle, but unable to read the "Revision Id" from the slave device i.e MAX14830 expander chip.Whatever data write on the MOSI, refect and observed on the oscilloscope. But not received any data on the MISO line, which is expected. Means communication not established.
If we consider problem with slave, but for the gpio chip select able to read the revision id and communication works.

We are using the 4.9.x nxp kernel.

What could be the problem? Is any known problem with native chip select ?

Is anyone already faced similar issue with native chip select ? How to solve ?