BeagleBone Black/Green SPI pins always low with 4.1.22 kernel

[Grzesiek Stawik]

So i had this other issue where the power button would not trigger poweroff, and from time to time i try new kernel versions to see if it works, and i have recently switched to 4.1.22 because it does work there.

But.

Strange things happen with SPI in 4.1.22, spidev is now created as /dev/spidev2.X instead /dev/spidev1.X, or, when using "cape-universal" overlay, i get both /dev/spidev1.X and /dev/spidev2.X but none of them are working.

What i mean by " SPI not working".

I can get the kernel to create /dev/spidevX.X, i can open it, write to it, read from it etc, however, it does not trigger ANY electrical change on physical SPI bus pins, none. I have been fiddling with device tree overlay sources, without success.

I have my oscilloscope connected and MISO/MOSI lines are not even hoing high during transmision ( they are suppose to go high as soon as /dev/spidevX.X is created ).

So i am swapping uname_r value in uEnv.txt to switch between kernels and compare the results, and so far in 4.1.1 spi is working fine, and in 4.1.22 spi is a black hole, pretending to work, and has absolutely no effect on physical spi pins on the cpu.

I HAVE TRIED 4.1.22 kernel from diffrent pre-builds and from sources.

TL;DR

On kernel 4.1.22, spi bus pins are always low.

[evilwulfie]

On the console image if you want the power button to function you install  acpid
It will shutdown the bbb on power button press AND if a battery is connected will shutdown the bbb as well

As far as spi goes have you tried  BB-SPIDEV1-00A0.dtbo or BB-SPIDEV0-00A0.dtbo?

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[Robert Nelson]

On Fri, Apr 29, 2016 at 11:08 AM, Grzesiek Stawik <sta...@gmail.com> wrote:

So i had this other issue where the power button would not trigger poweroff, and from time to time i try new kernel versions to see if it works, and i have recently switched to 4.1.22 because it does work there.

But.

Strange things happen with SPI in 4.1.22, spidev is now created as /dev/spidev2.X instead /dev/spidev1.X, or, when using "cape-universal" overlay, i get both /dev/spidev1.X and /dev/spidev2.X but none of them are working.

"cape-universal" just enables the peripheral out of the box..

When using it, you need to use "config-pin" to mux the pin's utilized..

Here is the readme:

https://github.com/cdsteinkuehler/beaglebone-universal-io/blob/master/README.md

the 'overlay' is already loaded by default.. you just need to use config-pin to setup the spidev pin's..

Regards,

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Robert Nelson
https://rcn-ee.com/

[Grzesiek Stawik]

Thanks, for the responses, let me clarify the problem.

In 4.1.1 i have been using overlays from "https://github.com/RobertCNelson/bb.org-overlays" and everything was working fine for the last year or so except the power button ( i gave up on this and don't remember the details, but issue was something about the power button device in /dev/ or /sys missing, and acpid not receiving any signal from the button )

so i have working system with 4.1.1 ( except the power button, which is a minor issue ).

i have recently upgraded, ONLY the kernel ( and modules, and firmware ) to 4.1.22, ( also later updated overlays from bb.org-overlays ) and now the power button works fine, but /dev/spidevX.X is dead.

if i simply boot the old kernel, spidev comes back to life.

again, from the system's point of view, on 4.1.22 everything is fine, spidev exists and i can use it, however no electrons are present on the physical spi pins.

Other overlays from bb.org-overlays are working fine on 4.1.22

Best Regards.

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[Mattt C]

Hi, 

I got the exact same problem. I use the DTBO BB-SPIDEV0 with linux kernel 4.1.15. The pinmux of SPI pins doesn't change when I load the SPI overlay. I tried loading I2C1, pin P9_18 change its pinmux. When I load SPIDEV0, it doesn't.

Best regards.

[Robert Nelson]

On Fri, May 27, 2016 at 8:29 AM, Mattt C <matthie...@gmail.com> wrote:

Hi, 

I got the exact same problem. I use the DTBO BB-SPIDEV0 with linux kernel 4.1.15. The pinmux of SPI pins doesn't change when I load the SPI overlay. I tried loading I2C1, pin P9_18 change its pinmux. When I load SPIDEV0, it doesn't.

BB-SPIDEV0 needs to be loaded at bootup, not later, as it will fail if manually loaded...

add it to /boot/uEnv.txt

cape_enable=bone_capemgr.enable_partno=BB-SPIDEV0

Regards,

[John Syne]

Hi Robert,

You are talking about the edma not being registered for the SPI when using overlays, right?

I’ve been working on adding DMA to the IIO ADC driver and I came across the same problem. It seems like prepare_unused_channel_list is only called the first time edma_alloc_channel is called. In prepare_unused_channel_list, it scans the device tree for “dmas” & “dma-cells” and sets up the edma_cc[0]->edma_unused. 

So similar to the problem you have with SPI, I had to add the ADC spec into the base devicetree because the overlay would not work. 

Regards,

John

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