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author | Ahmad Fatoum <ahmad@a3f.at> | 2020-11-28 22:39:34 +0100 |
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committer | Sascha Hauer <s.hauer@pengutronix.de> | 2020-12-10 10:47:15 +0100 |
commit | c06cd360830e83d4d916da3918a4f819d59230e9 (patch) | |
tree | 84b8d1b8e6e0abda59ec5aed0b02ef51163a48f5 | |
parent | eab7eedd2e5315e7dbb8f35277d095107edab57c (diff) | |
download | barebox-c06cd360830e83d4d916da3918a4f819d59230e9.tar.gz |
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.rst | 7 |
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); |