From: Renaud Barbier <renaud.barbier@ge.com>
To: linux-console@vger.kernel.org
Subject: ttySx probing
Date: Fri, 26 Jun 2015 14:44:22 +0100 [thread overview]
Message-ID: <558D5736.2080904@ge.com> (raw)
Hello,
I have a Freescale P1014 custom board with the UARTs connected as follows:
UART0 -> BMM (Board management device connected to sensors) ttyS0 115200
bauds
UART1 -> Not used. Disable in the device tree.
UART2 -> Console. ttyS1 - 9600 bauds
UART3 -> Not used. ttyS2
I am using Linux 3.14
The bootargs specifices console=ttyS1,9600n8
I have two issues:
When booting a few lines of garbage characters are printed when ttyS0 is
probed.
serialªrÒÒ¢ÑåMÅÑyS0 at MMIO 0xffe04500 (irq = 42, base_baud = 20833333)
is a 165
ÑÑ55%=ÁááÁÑÝÁÁÑ¡¥ÉÅÉõÑɱõ±
ÍÍ}½¹Íͽ¹Íͽ±mÕÕѹ¹ loaded
±5)½½Ñ½¹Íͽ±mÕÕÍÍ
5)½½ÑÑ
...
Later the system reached the prompt.
These type of character also appears when setting UART0 to 9600/115200
bauds in the boot loader or not programming the speed at all.
This does not happen when UART0 is disabled in the device tree.
I do not understand why Linux would attempt to use ttyS0 when the
console is specified as ttyS1. Is there a way to prevent this behaviour?
Next, if I do not program a baud rate in UART0 from the boot loader and
use for instance the command stty -F /dev/ttyS0. There is an interrupt
flood and Linux hangs. The same happen when using the tools accessing
the BMM. No character seems to be transmitted or received.
Note that I need to spent for time gathering data on this issue.
I am looking for a way to solve the first issue. I was thinking to get
ttyS1 (UART2) to be probed first and see whether that would prevent
these characters from being printed or any other possible solution to
test. Though, I am not sure how this can be accomplished after looking
at boot argument controlling console access or changing the device tree.
I would appreciate any suggestions.
Cheers,
Renaud
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reply other threads:[~2015-06-26 13:44 UTC|newest]
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