linux-kernel - Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console

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Message-ID: <20170911110522.vwgwnohjrrj2twtk@bivouac.eciton.net>
Date:   Mon, 11 Sep 2017 12:05:22 +0100
From:   Leif Lindholm <leif.lindholm@...aro.org>
To:     Andreas Schwab <schwab@...e.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        linux-serial@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Russell King <linux@....linux.org.uk>,
        Len Brown <lenb@...nel.org>,
        Graeme Gregory <graeme.gregory@...aro.org>,
        Al Stone <ahs3@...hat.com>,
        Christopher Covington <cov@...eaurora.org>,
        Yury Norov <ynorov@...iumnetworks.com>,
        Peter Hurley <peter@...leysoftware.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        "Zheng, Lv" <lv.zheng@...el.com>, Mark Salter <msalter@...hat.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Jiri Slaby <jslaby@...e.com>
Subject: Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console

I'm afraid Aleksey is no longer assigned to Linaro (you will probably
have seen a bounce).

On Mon, Sep 11, 2017 at 11:11:49AM +0200, Andreas Schwab wrote:
> On Sep 27 2016, Aleksey Makarov <aleksey.makarov@...aro.org> wrote:
> 
> > 'ARM Server Base Boot Requiremets' [1] mentions SPCR (Serial Port
> > Console Redirection Table) [2] as a mandatory ACPI table that
> > specifies the configuration of serial console.
> >
> > Defer initialization of DT earlycon until ACPI/DT decision is made.
> >
> > Parse the ACPI SPCR table, setup earlycon if required,
> > enable specified console.
> 
> How can I tell the kernel to ignore this table and use the console on
> the command line instead?

I guess we could just ignore the table completely
	if (console_set_on_cmdline)
like its counterpart in of_console_check().

Like so (not tested beyond compile testing):

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 324b35bfe781..c3cf0f1ebb8f 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -96,6 +96,9 @@ int __init parse_spcr(bool earlycon)
        int baud_rate;
	        int err;

+       if (console_set_on_cmdline)
+               return 0;
+
        if (acpi_disabled)
	                return -ENODEV;

Are you asking because you want to use a different console in a lab
setup or because there are issues with SPCR on your platform?

/
    Leif