RPi3: serial console

RPi3: serial console

[Heinrich Schuchardt]

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 observe this both with rpi_3_defconfig and rpi_arm64_defconfig,
v2020.10 and current origin/master.

config.txt:

arm_control=0x200
enable_uart=1
upstream_kernel=1
kernel=u-boot.bin

boot.scr:
setenv autoload no
dhcp
load mmc 0:1 $fdt_addr_r bcm2710-rpi-3-b-plus.dtb
load mmc 0:2 $kernel_addr_r EFI/debian/grubaa64.efi
bootefi $kernel_addr_r $fdt_addr_r

Best regards

Heinrich

RPi3: serial console

[Peter Robinson]

On Mon, Oct 12, 2020 at 3:56 PM Heinrich Schuchardt <xypron.glpk@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.

> I observe this both with rpi_3_defconfig and rpi_arm64_defconfig,
> v2020.10 and current origin/master.
>
> config.txt:
>
> arm_control=0x200
> enable_uart=1
> upstream_kernel=1
> kernel=u-boot.bin
>
> boot.scr:
> setenv autoload no
> dhcp
> load mmc 0:1 $fdt_addr_r bcm2710-rpi-3-b-plus.dtb
> load mmc 0:2 $kernel_addr_r EFI/debian/grubaa64.efi
> bootefi $kernel_addr_r $fdt_addr_r
>
> Best regards
>
> Heinrich

RPi3: serial console

[Heinrich Schuchardt]

On 10/12/20 6:50 PM, Peter Robinson wrote:
> On Mon, Oct 12, 2020 at 3:56 PM Heinrich Schuchardt <xypron.glpk@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.

Best regards

Heinrich

>
>> I observe this both with rpi_3_defconfig and rpi_arm64_defconfig,
>> v2020.10 and current origin/master.
>>
>> config.txt:
>>
>> arm_control=0x200
>> enable_uart=1
>> upstream_kernel=1
>> kernel=u-boot.bin
>>
>> boot.scr:
>> setenv autoload no
>> dhcp
>> load mmc 0:1 $fdt_addr_r bcm2710-rpi-3-b-plus.dtb
>> load mmc 0:2 $kernel_addr_r EFI/debian/grubaa64.efi
>> bootefi $kernel_addr_r $fdt_addr_r
>>
>> Best regards
>>
>> Heinrich

RPi3: serial console

[Otavio Salvador]

Hello,

Em seg., 12 de out. de 2020 ?s 15:39, Heinrich Schuchardt
<xypron.glpk@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@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
http://www.ossystems.com.br        http://code.ossystems.com.br
Mobile: +55 (53) 9 9981-7854          Mobile: +1 (347) 903-9750

RPi3: serial console

[Peter Robinson]

> >> 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.

For reference I have found a number of other problems with recent
firmwares and 2020.10 release:
* U-Boot crashes on a RPi4 8Gb model if you don't have a display connected [1]
* It doesn't boot, not sure if it's a crash or something else, you
just get the rainbow screen, if you don't have the uart enabled in
config.txt (ie just using a display for output).

Both of these seem to be due to firmware changes as opposed to U-Boot
changes, as it was working fine on the firmware from Apr 1st, but
there's been various other issues there like the 8Gb model doesn't
completely work.

[1] https://lists.denx.de/pipermail/u-boot/2020-September/428156.html

> 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.
>
> Best regards
>
> Heinrich
>
> >
> >> I observe this both with rpi_3_defconfig and rpi_arm64_defconfig,
> >> v2020.10 and current origin/master.
> >>
> >> config.txt:
> >>
> >> arm_control=0x200
> >> enable_uart=1
> >> upstream_kernel=1
> >> kernel=u-boot.bin
> >>
> >> boot.scr:
> >> setenv autoload no
> >> dhcp
> >> load mmc 0:1 $fdt_addr_r bcm2710-rpi-3-b-plus.dtb
> >> load mmc 0:2 $kernel_addr_r EFI/debian/grubaa64.efi
> >> bootefi $kernel_addr_r $fdt_addr_r
> >>
> >> Best regards
> >>
> >> Heinrich
>

RPi3: serial console

[Ricardo Salveti]

On Tue, Oct 13, 2020 at 11:04 AM Peter Robinson <pbrobinson@gmail.com> 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.
>
> For reference I have found a number of other problems with recent
> firmwares and 2020.10 release:
> * U-Boot crashes on a RPi4 8Gb model if you don't have a display connected [1]
> * It doesn't boot, not sure if it's a crash or something else, you
> just get the rainbow screen, if you don't have the uart enabled in
> config.txt (ie just using a display for output).

Noticed the same as well here (boots fine only with enable_uart=1).
While playing over with the files I noticed it works fine with the
latest firmware when using an older bcm2710-rpi-3-b-plus.dtb
(placed together with the firmware). If I use the latest
bcm2710-rpi-3-b-plus.dtb from the 5.4 downstream kernel, it doesn't
work (only tested on rpi3-b-plus).

This is with CONFIG_OF_BOARD=y, if I use CONFIG_OF_EMBED instead it
works just fine (which gives me the impression that u-boot might not
be happy with the dtb generated by the firmware when enable_uart is
not set).

Cheers,

--
Ricardo Salveti de Araujo

RPi3: serial console

[Stefan Agner]

On 2020-10-16 03:28, Ricardo Salveti wrote:
> On Tue, Oct 13, 2020 at 11:04 AM Peter Robinson <pbrobinson@gmail.com> 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.
>>
>> For reference I have found a number of other problems with recent
>> firmwares and 2020.10 release:
>> * U-Boot crashes on a RPi4 8Gb model if you don't have a display connected [1]
>> * It doesn't boot, not sure if it's a crash or something else, you
>> just get the rainbow screen, if you don't have the uart enabled in
>> config.txt (ie just using a display for output).
> 
> Noticed the same as well here (boots fine only with enable_uart=1).
> While playing over with the files I noticed it works fine with the
> latest firmware when using an older bcm2710-rpi-3-b-plus.dtb
> (placed together with the firmware). If I use the latest
> bcm2710-rpi-3-b-plus.dtb from the 5.4 downstream kernel, it doesn't
> work (only tested on rpi3-b-plus).
> 
> This is with CONFIG_OF_BOARD=y, if I use CONFIG_OF_EMBED instead it
> works just fine (which gives me the impression that u-boot might not
> be happy with the dtb generated by the firmware when enable_uart is
> not set).

What we noticed is adding brcm,bcm2835-pl011 compatible to the UARTs
makes U-Boot 2020.10 boot even *without* enable_uart=1. dm shows that
with this change CONFIG_BCM283X_PL011_SERIAL is in use...

From what I understand, this driver checks if the UART is muxed, and if
not bails out. So I guess without that compatible string, when the
regular PL011 driver is used, it seems that U-Boot tries to initialize
UART and fails?

--
Stefan

RPi3: serial console

[Stefan Agner]

On 2020-11-04 15:05, Stefan Agner wrote:
> On 2020-10-16 03:28, Ricardo Salveti wrote:
>> On Tue, Oct 13, 2020 at 11:04 AM Peter Robinson <pbrobinson@gmail.com> 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.
>>>
>>> For reference I have found a number of other problems with recent
>>> firmwares and 2020.10 release:
>>> * U-Boot crashes on a RPi4 8Gb model if you don't have a display connected [1]
>>> * It doesn't boot, not sure if it's a crash or something else, you
>>> just get the rainbow screen, if you don't have the uart enabled in
>>> config.txt (ie just using a display for output).
>>
>> Noticed the same as well here (boots fine only with enable_uart=1).
>> While playing over with the files I noticed it works fine with the
>> latest firmware when using an older bcm2710-rpi-3-b-plus.dtb
>> (placed together with the firmware). If I use the latest
>> bcm2710-rpi-3-b-plus.dtb from the 5.4 downstream kernel, it doesn't
>> work (only tested on rpi3-b-plus).
>>
>> This is with CONFIG_OF_BOARD=y, if I use CONFIG_OF_EMBED instead it
>> works just fine (which gives me the impression that u-boot might not
>> be happy with the dtb generated by the firmware when enable_uart is
>> not set).
> 
> What we noticed is adding brcm,bcm2835-pl011 compatible to the UARTs
> makes U-Boot 2020.10 boot even *without* enable_uart=1. dm shows that
> with this change CONFIG_BCM283X_PL011_SERIAL is in use...
> 
> From what I understand, this driver checks if the UART is muxed, and if
> not bails out. So I guess without that compatible string, when the
> regular PL011 driver is used, it seems that U-Boot tries to initialize
> UART and fails?

I looked a bit more into this and I think I made some progress.

This is with downstream Linux 5.4, but I don't think it is relevant as
downstream uses now the same UART bindings as upstream.

It seems when U-Boot is falling back to the Bluetooth (mini) UART and
crashes when using it as serial console. I noticed when setting
"enable_uart=0" and "dtoverlay=disable-bt" U-Boot does show a serial
console on the GPIO pins 14/15. The console is running on UART0, the
first PL011 UART:
 serial        0  [ + ]   serial_pl01x          |   |-- serial at 7e201000

Another method which works using "dtparam=uart0=off" and
"enable_uart=0", which essentially disables UART0 and UART1 in device
tree. U-Boot won't show a serial console, but the system boots...

I think the reason why adding "brcm,bcm2835-pl011" to compatible works
is because it makes probing of uart0 (the PL011 UART) in U-Boot fail,
and hence U-Boot won't fallback to this UARTs.

Note that "enable_uart=0" is equal to *not* setting enable_uart at all
according to documentation and confirmed in the discussion at
https://github.com/raspberrypi/firmware/issues/1483 (on RPi 3/4
anyways).

What I also noticed that uart2 makes trouble (which is also PL011 in
RPi4): "dtparam=uart0=off", "enable_uart=0" and "dtoverlay=uart2" make
sure that only uart2 is available to U-Boot. It makes the system crash
well...

Disabling CONFIG_PL01X_SERIAL (which is only possible with a Kconfig
change in arch/arm/Kconfig) makes the system boot in all cases...

--
Stefan