From mboxrd@z Thu Jan 1 00:00:00 1970 From: Renaud Barbier Subject: ttySx probing Date: Fri, 26 Jun 2015 14:44:22 +0100 Message-ID: <558D5736.2080904@ge.com> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Sender: linux-console-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="utf-8" To: linux-console@vger.kernel.org Hello, I have a Freescale P1014 custom board with the UARTs connected as follo= ws: UART0 -> BMM (Board management device connected to sensors) ttyS0 11520= 0 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=3DttyS1,9600n8 I have two issues: When booting a few lines of garbage characters are printed when ttyS0 i= s probed. serial=C2=AAr=C3=92=C3=92=C2=A2=C3=91=C3=A5M=C3=85=C3=91yS0 at MMIO 0xf= fe04500 (irq =3D 42, base_baud =3D 20833333) is a 165 =C3=91=C3=9155%=3D=C3=81=C3=A1=C3=A1=C3=81=C3=91=C3=9D=C3=81=C3=81=C3=91= =C2=A1=C2=A5=C3=89=C3=85=C3=89=C3=B5=C3=91=C3=89=C2=B1=C3=B5=C2=B1 =C3=8D=C3=8D}=C2=BD=C2=B9=C3=8D=C3=8D=C2=BD=C2=B9=C3=8D=C3=8D=C2=BD=C2=B1= m=C3=95=C3=95=C3=91=C2=B9=C2=B9 loaded =C2=B15)=C2=BD=C2=BD=C3=91=C2=BD=C2=B9=C3=8D=C3=8D=C2=BD=C2=B1m=C3=95=C3= =95=C3=8D=C3=8D 5)=C2=BD=C2=BD=C3=91=C3=91 =2E.. 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 an= d 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= =2E I would appreciate any suggestions. Cheers, Renaud -- To unsubscribe from this list: send the line "unsubscribe linux-console= " in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html