Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
MIME-Version: 1.0
In-Reply-To: <CAGS+omCuEYSHFPmknvvvjUpCWFP_rCmwa9utQiO=aEmdm-anwg@mail.gmail.com>
References: <20180314003655.12141-1-djkurtz@chromium.org> <20180314003655.12141-2-djkurtz@chromium.org>
 <CAPybu_0uLNz=tRvwqnMfoogJ=A4b5SgMecE9ZihrZdFrbRvcEw@mail.gmail.com> <CAGS+omCuEYSHFPmknvvvjUpCWFP_rCmwa9utQiO=aEmdm-anwg@mail.gmail.com>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 14 Mar 2018 18:38:38 +0200
Message-ID: <CAHp75VehhNv6pPrRiM9jBAK9FsqZ2Defo8HKhutwn+GPnCFp3w@mail.gmail.com>
Subject: Re: [PATCH 1/3] serial: 8250_early: Add earlycon support for AMD
 Carrizo / Stoneyridge
To:     Daniel Kurtz <djkurtz@chromium.org>
Cc:     Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>,
        Aaron Durbin <adurbin@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jslaby@suse.com>,
        Marc Gonzalez <marc_gonzalez@sigmadesigns.com>,
        Doug Anderson <dianders@chromium.org>,
        Matt Redfearn <matt.redfearn@mips.com>,
        Jeffy <jeffy.chen@rock-chips.com>,
        "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Mar 14, 2018 at 6:29 PM, Daniel Kurtz <djkurtz@chromium.org> wrote:
> On Wed, Mar 14, 2018 at 4:54 AM Ricardo Ribalda Delgado <
> ricardo.ribalda@gmail.com> wrote:
>> On Wed, Mar 14, 2018 at 1:36 AM, Daniel Kurtz <djkurtz@chromium.org>
> wrote:

> In fact, the recommended way is to have firmware specify an ACPI SPCR table
> with OEMID="AMDCZ " (see https://patchwork.kernel.org/patch/10281307/) to
> configure proper access and address.

Hmm... I was thinking it's already there. And thus, this is just a
quirk for *existing* firmware that doesn't correctly configured
hardware.
(Yes, I'm aware about one nuance in SPCR specification I'm trying to
address via official ways)

>  With an SPCR table in place,  the
> kernel command line just becomes "earlycon", with no parameters.

SPCR *provides* an address of UART (required by specification).

-- 
With Best Regards,
Andy Shevchenko