From mboxrd@z Thu Jan 1 00:00:00 1970 From: Masahiro Yamada Subject: Re: Which is better to specify console, "console= " or "stdout-path" ? Date: Thu, 22 Oct 2015 00:38:15 +0900 Message-ID: References: <562753A6.3070107@arm.com> <56278911.9050704@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Return-path: In-Reply-To: <56278911.9050704-WaGBZJeGNqdsbIuE7sb01tBPR1lH4CV8@public.gmane.org> Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Peter Hurley Cc: Sudeep Holla , devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel , linux-serial-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: devicetree@vger.kernel.org Hi Peter. 2015-10-21 21:46 GMT+09:00 Peter Hurley : > On 10/21/2015 04:58 AM, Sudeep Holla wrote: >> On 21/10/15 06:09, Masahiro Yamada wrote: >>> I think there exist two ways to specify the console port and baudrate. >>> >>> >>> [1] Specify console in bootargs >>> >>> chosen { >>> bootargs = "console=ttyS0,115200"; >>> }; >>> >>> >>> [2] Specify stdout-path >>> >>> chosen { >>> stdout-path = "serial0:115200n8"; >> >> This will work for even early/boot console, so this is better than >> option [1] > > Be aware that options specified via /chosen/stdout-path are > currently ignored by earlycon. There were some hiccups getting the > initial support upstream; when 4.4 hits mainline, I'll resubmit > my series that implements the of_serial i/o properties and > options passthrough to earlycon setup. As I said in another thread ("serial: earlycon: allow to specify uartclk in earlycon kernel-parameter"), stdout-path can pass dev->baud, but not port->uartclk. It is usually specified "clocks" phandle, but clk is not ready at the point of earlycon. It seems impossible to set up the baudrate even if the options are passed. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: yamada.masahiro@socionext.com (Masahiro Yamada) Date: Thu, 22 Oct 2015 00:38:15 +0900 Subject: Which is better to specify console, "console= " or "stdout-path" ? In-Reply-To: <56278911.9050704@hurleysoftware.com> References: <562753A6.3070107@arm.com> <56278911.9050704@hurleysoftware.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Peter. 2015-10-21 21:46 GMT+09:00 Peter Hurley : > On 10/21/2015 04:58 AM, Sudeep Holla wrote: >> On 21/10/15 06:09, Masahiro Yamada wrote: >>> I think there exist two ways to specify the console port and baudrate. >>> >>> >>> [1] Specify console in bootargs >>> >>> chosen { >>> bootargs = "console=ttyS0,115200"; >>> }; >>> >>> >>> [2] Specify stdout-path >>> >>> chosen { >>> stdout-path = "serial0:115200n8"; >> >> This will work for even early/boot console, so this is better than >> option [1] > > Be aware that options specified via /chosen/stdout-path are > currently ignored by earlycon. There were some hiccups getting the > initial support upstream; when 4.4 hits mainline, I'll resubmit > my series that implements the of_serial i/o properties and > options passthrough to earlycon setup. As I said in another thread ("serial: earlycon: allow to specify uartclk in earlycon kernel-parameter"), stdout-path can pass dev->baud, but not port->uartclk. It is usually specified "clocks" phandle, but clk is not ready at the point of earlycon. It seems impossible to set up the baudrate even if the options are passed. -- Best Regards Masahiro Yamada