[PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Paul Walmsley]

Kernels booting on RISC-V can specify "earlycon" with no options on
the Linux command line, and the generic DT earlycon support will query
the "chosen/stdout-path" property (if present) to determine which
early console device to use.  Document this appropriately in the
admin-guide.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Andreas Schwab <schwab@suse.de>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c7ac2f3ac99f..011fee969ece 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -990,6 +990,10 @@
 			[X86] When used with no options the early console is
 			determined by the ACPI SPCR table.
 
+			[RISCV] When used with no options, the early
+			console is determined by the stdout-path
+			property in the device tree's chosen node.
+
 		cdns,<addr>[,options]
 			Start an early, polled-mode console on a Cadence
 			(xuartps) serial port at the specified address. Only
-- 
2.23.0


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Re: [PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Geert Uytterhoeven]

On Wed, Oct 9, 2019 at 9:53 PM Paul Walmsley <paul.walmsley@sifive.com> wrote:
> Kernels booting on RISC-V can specify "earlycon" with no options on
> the Linux command line, and the generic DT earlycon support will query
> the "chosen/stdout-path" property (if present) to determine which
> early console device to use.  Document this appropriately in the
> admin-guide.
>
> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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Re: [PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Jonathan Corbet]

On Thu, 10 Oct 2019 09:10:18 +0200
Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> On Wed, Oct 9, 2019 at 9:53 PM Paul Walmsley <paul.walmsley@sifive.com> wrote:
> > Kernels booting on RISC-V can specify "earlycon" with no options on
> > the Linux command line, and the generic DT earlycon support will query
> > the "chosen/stdout-path" property (if present) to determine which
> > early console device to use.  Document this appropriately in the
> > admin-guide.
> >
> > Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>  
> 
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Applied, thanks.

jon

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Re: [PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Christoph Hellwig]

On Wed, Oct 09, 2019 at 12:53:50PM -0700, Paul Walmsley wrote:
> 
> Kernels booting on RISC-V can specify "earlycon" with no options on
> the Linux command line, and the generic DT earlycon support will query
> the "chosen/stdout-path" property (if present) to determine which
> early console device to use.  Document this appropriately in the
> admin-guide.

Jon already applied a patch from me removing the bogus arch restrictions
on the earlycon without arguments documentation, so this should not
be required.

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Re: [PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Christoph Hellwig]

Jon,

can you please revert this?  The paragraph above this addition already
describes the riscv case perfecty well with my previous patch:


	earlycon=	[KNL] Output early console device and options.

			When used with no options, the early console is
			determined by stdout-path property in device tree's
			chosen node or the ACPI SPCR table if supported by
			the platform.

			[RISCV] When used with no options, the early
			console is determined by the stdout-path
			property in the device tree's chosen node.

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Re: [PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Paul Walmsley]

Hi Jon,

On Fri, 8 Nov 2019, Christoph Hellwig wrote:

> can you please revert this?  The paragraph above this addition already
> describes the riscv case perfecty well with my previous patch:
> 
> 	earlycon=	[KNL] Output early console device and options.
> 
> 			When used with no options, the early console is
> 			determined by stdout-path property in device tree's
> 			chosen node or the ACPI SPCR table if supported by
> 			the platform.
> 
> 			[RISCV] When used with no options, the early
> 			console is determined by the stdout-path
> 			property in the device tree's chosen node.

I support reverting the RISCV section, now that Christoph's more general 
change has gone in.



- Paul

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Re: [PATCH] Documentation: admin-guide: add earlycon documentation for RISC-V

[Jonathan Corbet]

On Mon, 11 Nov 2019 17:30:13 +0000 (UTC)
Paul Walmsley <paul@pwsan.com> wrote:

> On Fri, 8 Nov 2019, Christoph Hellwig wrote:
> 
> > can you please revert this?  The paragraph above this addition already
> > describes the riscv case perfecty well with my previous patch:
> > 
> > 	earlycon=	[KNL] Output early console device and options.
> > 
> > 			When used with no options, the early console is
> > 			determined by stdout-path property in device tree's
> > 			chosen node or the ACPI SPCR table if supported by
> > 			the platform.
> > 
> > 			[RISCV] When used with no options, the early
> > 			console is determined by the stdout-path
> > 			property in the device tree's chosen node.  
> 
> I support reverting the RISCV section, now that Christoph's more general 
> change has gone in.

OK, the patch has been reverted.

Thanks,

jon

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