From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from relay8-d.mail.gandi.net ([217.70.183.201]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kj7wa-0002Ss-Da for barebox@lists.infradead.org; Sat, 28 Nov 2020 21:39:51 +0000 From: Ahmad Fatoum Date: Sat, 28 Nov 2020 22:39:34 +0100 Message-Id: <20201128213934.681065-11-ahmad@a3f.at> In-Reply-To: <20201128213934.681065-1-ahmad@a3f.at> References: <20201128213934.681065-1-ahmad@a3f.at> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "barebox" Errors-To: barebox-bounces+u.kleine-koenig=pengutronix.de@lists.infradead.org Subject: [PATCH 11/11] doc: bcm283x: document use of mini-uart on Raspberry Pi Zero W / CM3 To: barebox@lists.infradead.org Cc: Andrew John , Roland Hieber , Robert Carnecky , Rouven Czerwinski 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 Cc: Rouven Czerwinski Cc: Robert Carnecky Cc: Andrew John Signed-off-by: Ahmad Fatoum --- 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. + (For more information, refer to the `documentation for config.txt`_.) 5. Connect to board's UART (115200 8N1); -- 2.28.0 _______________________________________________ barebox mailing list barebox@lists.infradead.org http://lists.infradead.org/mailman/listinfo/barebox