[yocto] [meta-raspberrypi] Issue with 8250/16550 UART1 access in raspberrypi (meta-raspberrypi)

[Valentin Le bescond]

Hi !

I'm really no expert but am very interested in the subject.

Did you modify the device tree ? From what I understand in the DT that
you'll find pinmux definition right ?

Regards.


2015-06-04 14:01 GMT+02:00 Andreas Enbacka <andreas.enbacka at gasera.fi>:

> Hello,
>
>
>
> After a long break, I have returned to the Yocto project, and generally
> very pleased. A lot of progress has been done since I last used the project
> (two years ago), and now in my opinion everything works very smoothly.
>
>
>
> I have used yocto to build a custom image for the RaspberryPi Compute
> Module. Generally everything works ok, however I am experiencing problem
> with accessing the UART1 port on the raspberryPi. I am using a library
> called wiringPi to put the appropriate GPIO pins in the correct mode (alt5)
> for RXD1/TXD1 (pins 32/33). Also I have used menuconfig to enable the
> 8250/16550 serial port support in the kernel (3.18.5+). After booting the
> image I examined the dmesg output, and it shows following information
> related to 8250/16550:
>
> ..
>
> [   1.010958] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
>
> [   1.013920] serial8250.0: ttyS0 at MMIO 0x20215040 (irq = 29, base_baud
> = 7812500) is a 8250
>
> …
>
>
>
> Then I put the pins 32/33 into alternative mode alt5, and try to connect
> to the port /dev/ttyS0 using minicom (baud 115200). Trying to enter
> something into the Mincom terminal does not give any indications on our
> connected oscilloscope (connected to the relevant pins), however change of
> the alt mode earlier was observed correctly. The serial port should not be
> using any flow control, but when trying to disable the flow control using
> Minicom (it was on by default) freezes the complete RaspberryPi system
> (requiring to disconnect and reconnect power).
>
>
>
> Does anyone have any thoughts what could be the cause of these issues
> (e.g., problems with driver etc)? Any information would be greatly
> appreciated. In the project we are working on we would need to use both
> uart ports (0/1) provided by the compute module (the uart0 is a pl011 and
> by disabling console use of /dev/ttyAMA0 we were able to successfully
> connect to that port).
>
>
>
> Thanks for the great work with the Yocto platform.
>
>
>
> Sincerely,
>
> Andreas Enbacka
>
> SW designer
>
> Gasera Ltd
>
>
>
> --
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>
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