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UART3 mikrobus ttymxc2 doesn't work on HBE #44

Closed ljburtz closed 6 years ago

ljburtz commented 7 years ago

HBE v1.2 SoM i1 solo v1.3 (same results with v1.5 also) sr-imx6-debian-jessie-cli-20160226.img

there is a simple patch in a thread on the forum : http://forum.solid-run.com/linux-on-cubox-i-and-hummingboard-f8/uart3-ttymxc2-mikrobus-nothing-happens-and-uart2-t-t3100.html>

I'm wondering why TX and RX were swapped and why it had 0x40013000 instead of 0x1b0b1 Note also: the fix includes disabling both the TX and RX UART DMA drivers

ljburtz commented 7 years ago

update on the DMA:

test imx6qdl-hummingboard2.dtsi result
both DMA disabled dma-names = "", ""; works both ways
RX DMA enabled / TX DMA disabled dma-names = "rx", ""; works both ways **
RX DMA disabled / TX DMA enabled dma-names = "", "tx"; works both ways
both DMA enabled dma-names = "rx", "tx"; sending from the HBE works / receiving doesn’t work
both DMA enabled but swapped dma-names = "tx", "rx"; sending from the HBE works / receiving doesn’t work

(all above tests include the modified pinctrl lines as described in the patch on the forum )

** but when starting loopback test, dmesg shows : [ 25.284882] imx-uart 21ec000.serial: cannot get the TX DMA channel!

jnettlet commented 6 years ago

This was an issue that has been fixed in newer board spins. It has been fixed in newer kernel releases but there is no way to detect the board revision programmatically. If you are still having problems please open a new bug based on the latest device-tree changes and we will look into it.