RPi3: serial console

[Otavio Salvador]

Hello,

Em seg., 12 de out. de 2020 às 15:39, Heinrich Schuchardt
<xypron.glpk at gmx.de> escreveu:
> On 10/12/20 6:50 PM, Peter Robinson wrote:
> > On Mon, Oct 12, 2020 at 3:56 PM Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
> >>
> >> Hello Matthias,
> >>
> >> I have upgraded the Raspberry 3 firmware from raspi3-firmware
> >> (1.20190215-1+deb10u4) to raspi-firmware (1.20200601-3)
> >> [https://packages.debian.org/bullseye/raspi-firmware].
> >>
> >> After the upgrade the output of U-Boot on the serial console is complete
> >> gibberish as if the baudrate were incorrect. The output from the Linux
> >> kernel is fine at 115200 baud.
> >
> > I've seen similar on all firmware since around mid April up until
> > recently, it seems to be fixed with releases in Oct (I'm using one
> > from Oct 8th), I'm not sure if it can be fixed in U-Boot but it seems
> > to be due to a change in the firmware.
>
> Thanks for confirming the problem.
>
> Using the most current files from
> https://github.com/raspberrypi/firmware does not solve the problem for me.
>
> In bcm283x_mu_serial_setbrg() we divide a clock rate by the baudrate.
> divider = plat->clock / (baudrate * 8);
>
> If we do not have the correct clock rate, the actual baudrate will be wrong.

It seems if you have the dtb files next to the firmware, the firmware
loads it and the baudrate seems right. We've been struggling with this
at our side as well and this was the only way we got it to work.

-- 
Otavio Salvador                             O.S. Systems
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