From: Matthias Brugger <matthias.bgg@gmail.com>
To: u-boot@lists.denx.de
Subject: Garbage UART output on RPI 4 with upstream kernel DTB
Date: Mon, 23 Dec 2019 21:20:05 +0100 [thread overview]
Message-ID: <50134995-68f7-c30a-5e48-ec8469f26e39@gmail.com> (raw)
In-Reply-To: <0cf7d0c0-7e9b-cd09-e15c-f906365ecd63@i2se.com>
Hi Stefan,
On 23/12/2019 19:51, Stefan Wahren wrote:
> Am 20.12.19 um 14:58 schrieb Stefan Wahren:
>> Hi,
>>
>> i tried to run current U-Boot (rpi_4_32b_defconfig) on my RPi 4 with
>> bcm2711-rpi-4-b.dtb from the upstream kernel. Unfortunately i only see
>> garbage on the debug UART (pin 14 & 15). Using the DTB from the
>> downstream kernel has a proper UART output. The config.txt contains
>> debug_uart=1
>>
>> I compared both and identified an offending Linux commit:
>> ARM: dts: bcm283x: Remove brcm,bcm2835-pl011 compatible
>>
>> Unfortunately reverting this patch still doesn't fix the issue. Any ideas?
>
> After hours of playing with the DTB, i finally found the reason why the
> upstream kernel DTB doesn't work with U-Boot on RPI 4. The DTS must be
> compiled with flag "-@".
>
> It isn't clear to me, why this is necessary but it would be nice to make
> U-Boot work without this.
>
Can you provide the exact command you are using?
Regards,
Matthias
next prev parent reply other threads:[~2019-12-23 20:20 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-20 13:58 Garbage UART output on RPI 4 with upstream kernel DTB Stefan Wahren
2019-12-23 18:51 ` Stefan Wahren
2019-12-23 20:20 ` Matthias Brugger [this message]
2019-12-24 11:56 ` Stefan Wahren
2019-12-24 12:38 ` Matthias Brugger
2019-12-25 13:55 ` Stefan Wahren
2020-01-13 12:45 ` Matthias Brugger
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