topic Re: ls1028a using lpuart (dma tx/rx channel request failed) in Layerscape

ls1028a using lpuart (dma tx/rx channel request failed)

pjw — Wed, 21 Oct 2020 01:43:53 GMT

Hi, I'm developing a custom board using ls1028a.

I added lpuart to dtsi to use lpuart,

lpuart2: serial@2280000 {
compatible = "fsl,ls1028a-lpuart";
reg = <0x0 0x2280000 0x0 0x1000>;
interrupts = <GIC_SPI 234 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clockgen 4 1>;
clock-names = "ipg";
little-endian;
status = "okay";
};

and added it to dts as follows.

&lpuart2 {
status = "okay";
};

After creating and checking the image file, ttyLP0 was created under /dev. But when I checked because there was no communication, I found the following log.

root@TinyLinux:~# dmesg | grep lpuart
[ 3.465382] fsl-lpuart 2280000.serial: DMA tx channel request failed, operating without tx DMA
[ 3.474030] fsl-lpuart 2280000.serial: DMA rx channel request failed, operating without rx DMA
[ 3.492118] fsl-lpuart 2290000.serial: DMA tx channel request failed, operating without tx DMA
[ 3.500765] fsl-lpuart 2290000.serial: DMA rx channel request failed, operating without rx DMA

I think it's a problem that doesn't have access to DMA, but it's hard to determine whether it's a hardware problem or a software problem.

For your information, the basic uart works properly.

I'd appreciate it if you could give me an answer.

Re: ls1028a using lpuart (dma tx/rx channel request failed)

ufedor — Wed, 21 Oct 2020 02:50:33 GMT

Please provide U-Boot booting log showing the RCW.

Re: ls1028a using lpuart (dma tx/rx channel request failed)

pjw — Wed, 21 Oct 2020 04:08:01 GMT

Hi.

Here is..

Reset Configuration Word (RCW):
00000000: 3c004010 00000030 00000000 00000000
00000010: 00000000 018f0000 0030c000 00000000
00000020: 01e031a0 00002580 00000000 010db291
00000030: 00000000 00000010 00000000 00000000
00000040: 00000000 00000000 00000000 00000000
00000050: 00000000 00000000 00000000 00000000
00000060: 00000000 00000000 100e7012 00000000
00000070: bb580000 00000000

I changed

XSPI1_A_DATA74_PMUX[369:367]

XSPI1_A_DATA30_PMUX[372:370]

for using LPUART2 / 3

and some other gpio pins.The clock side did not change because there was no change in hardware.

Thank you.

Re: ls1028a using lpuart (dma tx/rx channel request failed)

ufedor — Wed, 21 Oct 2020 06:33:55 GMT

Please provide complete U-Boot and Linux booting logs and log of the LPUART testing in Linux as ZIP archive attachment.

Re: ls1028a using lpuart (dma tx/rx channel request failed)

pjw — Wed, 21 Oct 2020 07:53:17 GMT

u- boot log and kernel log and testing log lpuart

The lpuart test was done using echo and nothing appears on the serial program.

Thank you

Re: ls1028a using lpuart (dma tx/rx channel request failed)

ufedor — Thu, 22 Oct 2020 14:18:53 GMT

> I think it's a problem that doesn't have access to DMA, but it's hard

> to determine whether it's a hardware problem or a software problem.

No, it's not a problem, LPUART can operate without DMA. Read the message, in fact:

DMA tx channel request failed, **operating without tx DMA**

DMA rx channel request failed, **operating without rx DMA**

If you were to add DMA channels, you would use the "dmas" and "dma-names"

device tree properties. Read the documentation for more details:

https://elixir.bootlin.com/linux/v5.9/source/Documentation/devicetree/bindings/serial/fsl-lpuart.txt

What logic level are you using for interfacing with the LPUART? 1.8V, right?

Does anything get output if you add console=/dev/ttyLP0,115200 to the kernel boot arguments?