Hello, On 29.11.20 20:50, Roland Hieber wrote: > On Sat, Nov 28, 2020 at 10:39:34PM +0100, Ahmad Fatoum wrote: >> As described in the UART configuration[1] article in the Raspberry Pi >> Foundation documentation, Raspberry Pi 3 & 4 as well as Zero W use the >> mini-uart as primary (easily user-accessible) UART. At least on the >> Raspberry Zero W and CM3, we need to pass uart_2ndstage=1, so the >> BootROM leaves the 8250 IP in a suitable state for use by barebox. >> Document this. >> >> [1]: https://www.raspberrypi.org/documentation/configuration/uart.md >> >> Cc: Roland Hieber <rhi@xxxxxxxxxxxxxx> >> Cc: Rouven Czerwinski <rcz@xxxxxxxxxxxxxx> >> Cc: Robert Carnecky <robert@xxxxxxxxxxx> >> Cc: Andrew John <andrew@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> >> Signed-off-by: Ahmad Fatoum <ahmad@xxxxxx> >> --- >> Documentation/boards/bcm2835.rst | 7 +++++++ >> 1 file changed, 7 insertions(+) >> >> diff --git a/Documentation/boards/bcm2835.rst b/Documentation/boards/bcm2835.rst >> index c896871e0d82..dbdfc2633173 100644 >> --- a/Documentation/boards/bcm2835.rst >> +++ b/Documentation/boards/bcm2835.rst >> @@ -23,6 +23,13 @@ Raspberry Pi >> kernel=barebox.img >> enable_uart=1 >> >> + If you want to use the mini-uart instead of the PL011, you might need to additionally set:: >> + >> + uart_2ndstage=1 >> + >> + This is useful on newer boards like the Raspberry Pi Zero W and CM3, which route the >> + more easily accessible primary UART to the mini-uart. > > This seems to be non-optional on RPi Zero W, so I would word it more > strongly. > > With this series, at least barebox boots, which is better than in master > :-) However, I cannot get the stock kernel (/boot/kernel.img) to boot on > Zero W, and I cannot figure out why: > > barebox@RaspberryPi Zero W:/ cat /boot/config.txt > enable_uart=1 > kernel=barebox.img > uart_2ndstage=1 > barebox@RaspberryPi Zero W:/ global bootm.image=/boot/kernel.img > barebox@RaspberryPi Zero W:/ global bootm.oftree=/boot/bcm2708-rpi-0-w.dtb > barebox@RaspberryPi Zero W:/ global linux.bootargs.dyn.root="root=/dev/mmcblk0p2 rootfstype=ext4 rootwait rw" > barebox@RaspberryPi Zero W:/ bootm -v > > Loading ARM Linux zImage '/boot/kernel.img' > OS image not yet relocated > Passing control to ARM zImage handler > no OS load address, defaulting to 0x014e9000 > no initrd load address, defaulting to 0x01a18000 > Loading devicetree from '/boot/bcm2708-rpi-0-w.dtb' > commandline: console=ttyS1,115200n8 root=/dev/mmcblk0p2 rootfstype=ext4 rootwait rw > > Starting kernel at 0x014e9000, oftree at 0x01a18000... > Starting kernel in secure mode > > and then nothing happens at least for a minute. > > I tried leaving 'uart_2ndstage=1' out, leaving 'enable_uart=1' out, setting > 'console=ttyS1,115200n8' on the kernel command line, and setting > 'console=ttyAMA0,115200n8' (as before), but nothing helped. > > The same setup works on a RPI-1B (with bootm.oftree=/boot/bcm2708-rpi-b.dtb), > so at least there's that :) > > Did you do anything else for your Zero W? Can you try `boot rpi` instead? > > - Roland > >> + >> (For more information, refer to the `documentation for config.txt`_.) >> >> 5. Connect to board's UART (115200 8N1); >> -- >> 2.28.0 >> >> > -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
