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

Started byAndreas Schwab <schwab@suse.de>
First post2017-09-11 11:20 +0200
Last post2017-09-11 14:30 +0200
Articles 7 — 3 participants

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  Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Andreas Schwab <schwab@suse.de> - 2017-09-11 11:20 +0200
    Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Leif Lindholm <leif.lindholm@linaro.org> - 2017-09-11 13:10 +0200
      Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Andreas Schwab <schwab@suse.de> - 2017-09-11 13:40 +0200
        Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Andreas Schwab <schwab@suse.de> - 2017-09-11 14:30 +0200
          Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Graeme Gregory <graeme.gregory@linaro.org> - 2017-09-11 15:10 +0200
          Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Leif Lindholm <leif.lindholm@linaro.org> - 2017-09-11 15:30 +0200
        Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console Graeme Gregory <graeme.gregory@linaro.org> - 2017-09-11 14:30 +0200

#1730228 — Re: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console

FromAndreas Schwab <schwab@suse.de>
Date2017-09-11 11:20 +0200
SubjectRe: [PATCH v11 2/4] ACPI: parse SPCR and enable matching console
Message-ID<uot2P-Wk-39@gated-at.bofh.it>
On Sep 27 2016, Aleksey Makarov <aleksey.makarov@linaro.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?

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

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#1730282

FromLeif Lindholm <leif.lindholm@linaro.org>
Date2017-09-11 13:10 +0200
Message-ID<uouLf-2jC-5@gated-at.bofh.it>
In reply to#1730228
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@linaro.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

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#1730298

FromAndreas Schwab <schwab@suse.de>
Date2017-09-11 13:40 +0200
Message-ID<uovei-2An-1@gated-at.bofh.it>
In reply to#1730282
On Sep 11 2017, Leif Lindholm <leif.lindholm@linaro.org> wrote:

> 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?

The console from the SPCR is not the one forwarded by the BMC.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

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#1730318

FromAndreas Schwab <schwab@suse.de>
Date2017-09-11 14:30 +0200
Message-ID<uow0G-3dr-5@gated-at.bofh.it>
In reply to#1730298
On Sep 11 2017, Graeme Gregory <graeme.gregory@linaro.org> wrote:

> Considering the SPCR table in question seems mildly insane, you could
> always unload the SPCR in grub.

How do you "unload the SPCR"?  But in any case, console= should always
take precedence.

Andreas.

-- 
Andreas Schwab, SUSE Labs, schwab@suse.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."

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#1730338

FromGraeme Gregory <graeme.gregory@linaro.org>
Date2017-09-11 15:10 +0200
Message-ID<uowDo-3I9-15@gated-at.bofh.it>
In reply to#1730318
On 11 September 2017 at 13:28, Andreas Schwab <schwab@suse.de> wrote:
> On Sep 11 2017, Graeme Gregory <graeme.gregory@linaro.org> wrote:
>
>> Considering the SPCR table in question seems mildly insane, you could
>> always unload the SPCR in grub.
>
> How do you "unload the SPCR"?  But in any case, console= should always
> take precedence.
>
Ah apologies, I thought the acpi command in grub could delete a table,
but it seems it cannot.

Graeme

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#1730356

FromLeif Lindholm <leif.lindholm@linaro.org>
Date2017-09-11 15:30 +0200
Message-ID<uowWJ-3Qa-9@gated-at.bofh.it>
In reply to#1730318
On Mon, Sep 11, 2017 at 02:28:20PM +0200, Andreas Schwab wrote:
> On Sep 11 2017, Graeme Gregory <graeme.gregory@linaro.org> wrote:
> 
> > Considering the SPCR table in question seems mildly insane, you could
> > always unload the SPCR in grub.
> 
> How do you "unload the SPCR"?  But in any case, console= should always
> take precedence.

I am not saying it shouldn't. But you should probably talk to your
supplier with regards to fixing their system.

The BMC knows which console you are attached to, and the firmware
still instructs the kernel to use something else.

/
    Leif

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#1730320

FromGraeme Gregory <graeme.gregory@linaro.org>
Date2017-09-11 14:30 +0200
Message-ID<uow0G-3dr-7@gated-at.bofh.it>
In reply to#1730298
On 11 September 2017 at 12:39, Andreas Schwab <schwab@suse.de> wrote:
> On Sep 11 2017, Leif Lindholm <leif.lindholm@linaro.org> wrote:
>
>> 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?
>
> The console from the SPCR is not the one forwarded by the BMC.
>
Considering the SPCR table in question seems mildly insane, you could
always unload the SPCR in grub.

Graeme

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