i.MX Processors中的主题 Re: Adding SPI-SLAVE mode to an older kernel version

Adding SPI-SLAVE mode to an older kernel version

Yavuz — Mon, 07 Sep 2020 10:09:45 GMT

Hi Everybody,

I have a few questions related to LINUX SPI concepts and SLAVE MODE implementations.

I am trying to port an IMX6 board to embedded linux by yocto from another operating system. Right now I need to port one SPI SLAVE MODE peripheral and one SPI MASTER MODE peripheral to port.

Linux-imx kernel version is 4.9.88. It is coming from yocto packages released by NXP.

I have added 2 spi devices using spidev userspace driver and tested with spidev_test loopback test. On loopback test it seem successful. But both are in SPI MASTR MODE.

When I checked the concepts of SPI on linux I encountered 2 nice videos on youtube

"https://www.youtube.com/watch?v=tCa_ydVwKhM&list=WL&index=3&t=0s"

"https://www.youtube.com/watch?v=MV8Sy6jGUIE&list=WL&index=2&t=0s"

First one defines slave mode support on linux and later one explains SPI subsystem on Linux kernel.

An far as I understand the SPI slave implementation is in LINUX Kernel.

Q1 Is it ready to use for an IMX6 system? If I had a newer version of kernel would it be easily implemented? Is there such an example that works for imx-yocto-bsp for imx6 SPI slave mode?

Q2 Can I port the SLAVE MODE capability from later kernels to my kernel version 4.9.88? How can i do that?

Q3 Is controller driver spi-imx.c used for this purpose? On device tree can i specify spidev as "compatible" parameter? How will spidev userspace driver use spi-imx.c as a control driver? How is the connection between protocol driver (userspace driver) and controller driver is established?

Q4 May be is it possible to change my linux-imx version to a kernel that supports spi slave mode functionality? It also needs to be supported by a yocto environment.

I know these are quite wide and unclear questions but it is so because my mind is also confused on concepts.

I hope to clarify these issues by your answers.

Best Regards

Yavuz

Re: Adding SPI-SLAVE mode to an older kernel version

Yuri — Mon, 07 Sep 2020 11:31:14 GMT

@Yavuz
Hello,

look at the following thread, hope it helps.

https://community.nxp.com/t5/i-MX-Processors/ECSPI-slave-mode-support-for-iMX6/m-p/767130#M119124

Regards,
Yuri.

Re: Adding SPI-SLAVE mode to an older kernel version

Yavuz — Tue, 08 Sep 2020 02:24:47 GMT

Thank You @Yuri for your response,

I checked "https://community.nxp.com/t5/i-MX-Processors/ECSPI-slave-mode-support-for-iMX6/m-p/767130#M119124"

it is definitely the same kind of problem.

But the thread you referred do not explain how to do that?

which files are to be updated for this purpose?

and how can i test it?

Regards

Re: Adding SPI-SLAVE mode to an older kernel version

Yuri — Tue, 08 Sep 2020 06:55:45 GMT

@Yavuz

It is needed to rebuild the kernel; under Yocto:

By default it is not supported; the following sequence may be performed for SPIDEV :

$ bitbake linux-imx -c menuconfig

# select DEVICE DRIVERS -> SPI Support -> User mode SPI device driver support

$ bitbake linux-imx
$ bitbake core-image-minimal

Re: Adding SPI-SLAVE mode to an older kernel version

Yavuz — Tue, 06 Oct 2020 07:52:45 GMT

Hi,

I have decided not to port spi slave support to an older version of kernel but rather switched to a kernel version 5.4.24.

https://community.nxp.com/t5/i-MX-Processors/Which-imx-linux-version-shall-be-selected-for-porting-SPI-SLAVE/m-p/1161140#M162735

Best Regards