summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorAhmad Fatoum <ahmad@a3f.at>2020-11-28 22:39:34 +0100
committerSascha Hauer <s.hauer@pengutronix.de>2020-12-10 10:47:15 +0100
commitc06cd360830e83d4d916da3918a4f819d59230e9 (patch)
tree84b8d1b8e6e0abda59ec5aed0b02ef51163a48f5
parenteab7eedd2e5315e7dbb8f35277d095107edab57c (diff)
downloadbarebox-c06cd360830e83d4d916da3918a4f819d59230e9.tar.gz
barebox-c06cd360830e83d4d916da3918a4f819d59230e9.tar.xz
doc: bcm283x: document use of mini-uart on Raspberry Pi Zero W / CM3
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@pengutronix.de> Cc: Rouven Czerwinski <rcz@pengutronix.de> Cc: Robert Carnecky <robert@neopsis.com> Cc: Andrew John <andrew@mobius-embedded-systems.co.uk> Signed-off-by: Ahmad Fatoum <ahmad@a3f.at> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
-rw-r--r--Documentation/boards/bcm2835.rst7
1 files changed, 7 insertions, 0 deletions
diff --git a/Documentation/boards/bcm2835.rst b/Documentation/boards/bcm2835.rst
index c896871e0d..8af6a09c13 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 may need to additionally set::
+
+ uart_2ndstage=1
+
+ This is required on boards, like the Raspberry Pi Zero W, that use the mini-uart as the
+ primary UART. It is needed on boards like the CM3 as well if the mini-uart is to be used.
+
(For more information, refer to the `documentation for config.txt`_.)
5. Connect to board's UART (115200 8N1);