Documentation: admin-guide: add earlycon documentation for the sifive serial driver
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Message ID alpine.DEB.2.21.9999.1910081606370.11044@viisi.sifive.com
State New, archived
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  • Documentation: admin-guide: add earlycon documentation for the sifive serial driver
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Commit Message

Paul Walmsley Oct. 8, 2019, 11:08 p.m. UTC
Document earlycon usage for the SiFive serial port driver in the same
fashion as for the other serial port IP blocks, since the SiFive
serial port driver supports it.

Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
Reported-by: Andreas Schwab <schwab@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
---
 Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Geert Uytterhoeven Oct. 9, 2019, 6:56 a.m. UTC | #1
Hi Paul,

On Wed, Oct 9, 2019 at 1:09 AM Paul Walmsley <paul.walmsley@sifive.com> wrote:
> Document earlycon usage for the SiFive serial port driver in the same
> fashion as for the other serial port IP blocks, since the SiFive
> serial port driver supports it.
>
> Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>
> Reported-by: Andreas Schwab <schwab@suse.de>
> Cc: Christoph Hellwig <hch@lst.de>

Thanks for your patch!

Why do you need this?
I believe risc-v is DT-only, so if chosen/stdout-path is set up, just
passing "earlycon" (without any options) should work.

> ---
>  Documentation/admin-guide/kernel-parameters.txt | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index c7ac2f3ac99f..90becb00221b 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1106,6 +1106,12 @@
>                         address must be provided, and the serial port must
>                         already be setup and configured.
>
> +               sifive,<addr>
> +                       Start an early, polled-mode console on a SiFive
> +                       serial port at the specified address.  The port must
> +                       already be setup and configured.  Options are not
> +                       yet supported.
> +
>         earlyprintk=    [X86,SH,ARM,M68k,S390]
>                         earlyprintk=vga
>                         earlyprintk=sclp

Gr{oetje,eeting}s,

                        Geert
Andreas Schwab Oct. 9, 2019, 10:06 a.m. UTC | #2
On Okt 09 2019, Geert Uytterhoeven <geert@linux-m68k.org> wrote:

> I believe risc-v is DT-only, so if chosen/stdout-path is set up

If.  Currently, it isn't.

Andreas.
Geert Uytterhoeven Oct. 9, 2019, 10:55 a.m. UTC | #3
Hi Andreas,

On Wed, Oct 9, 2019 at 12:06 PM Andreas Schwab <schwab@suse.de> wrote:
> On Okt 09 2019, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > I believe risc-v is DT-only, so if chosen/stdout-path is set up
>
> If.  Currently, it isn't.

IC. So isn't it better to fix that, instead of pointing people to more obscure
legacy solutions?

Gr{oetje,eeting}s,

                        Geert
Paul Walmsley Oct. 9, 2019, 2:31 p.m. UTC | #4
Hi Geert,

On Wed, 9 Oct 2019, Geert Uytterhoeven wrote:

> On Wed, Oct 9, 2019 at 12:06 PM Andreas Schwab <schwab@suse.de> wrote:
> > On Okt 09 2019, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > > I believe risc-v is DT-only, so if chosen/stdout-path is set up
> >
> > If.  Currently, it isn't.
> 
> IC. So isn't it better to fix that, instead of pointing people to more obscure
> legacy solutions?

There's nothing that's RISC-V specific about the SiFive serial IP or 
its driver.  So the issue of whether RISC-V is DT-only or not probably 
shouldn't impact whether we document that the SiFive serial driver 
supports earlycon.

best regards,

- Paul

Patch
diff mbox series

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index c7ac2f3ac99f..90becb00221b 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -1106,6 +1106,12 @@ 
 			address must be provided, and the serial port must
 			already be setup and configured.
 
+		sifive,<addr>
+			Start an early, polled-mode console on a SiFive
+			serial port at the specified address.  The port must
+			already be setup and configured.  Options are not
+			yet supported.
+
 	earlyprintk=	[X86,SH,ARM,M68k,S390]
 			earlyprintk=vga
 			earlyprintk=sclp