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Date:   Thu, 14 Jul 2022 13:30:06 -0700
From:   Peter Delevoryas <peter@pjd.dev>
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     DTML <devicetree@vger.kernel.org>,
        linux-aspeed <linux-aspeed@lists.ozlabs.org>,
        Logananth Sundararaj <logananth13.hcl@gmail.com>,
        Andrew Jeffery <andrew@aj.id.au>,
        OpenBMC Maillist <openbmc@lists.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        naveen.mosess@hcl.com, thangavel.k@hcl.com,
        SoC Team <soc@kernel.org>, Rob Herring <robh+dt@kernel.org>,
        Joel Stanley <joel@jms.id.au>, Olof Johansson <olof@lixom.net>,
        garnermic@gmail.com, velumanit@hcl.com,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v3] The Yosemite V3.5 is a facebook multi-node server
 platform that host four OCP server. The BMC in the Yosemite V3.5 platform
 based on AST2600 SoC.
Message-ID: <YtB8zjhjwlUXp4Mw@pdel-mbp.dhcp.thefacebook.com>
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On Thu, Jul 14, 2022 at 01:24:59PM -0700, Peter Delevoryas wrote:
> On Thu, Jul 14, 2022 at 10:15:15PM +0200, Arnd Bergmann wrote:
> > On Thu, Jul 14, 2022 at 8:05 PM Peter Delevoryas <peter@pjd.dev> wrote:
> > > On Thu, Jul 07, 2022 at 03:33:48PM +0200, Arnd Bergmann wrote:
> > > > > +       model = "Facebook fby35";
> > > > > +       compatible = "facebook,fby35", "aspeed,ast2600";
> > > > > +
> > > > > +       aliases {
> > > > > +               serial4 = &uart5;
> > > > > +       };
> > > >
> > > > Why not start at serial0 here?
> > >
> > > Hey, Facebook person jumping in here (using a personal email):
> > >
> > > I think you're right, it should be like this:
> > >
> > >         aliases {
> > >                 serial0 = &uart5;
> > >                 serial1 = &uart1;
> > >                 serial2 = &uart2;
> > >                 serial3 = &uart3;
> > >                 serial4 = &uart4;
> > >         };
> > 
> > Are you actually using all five uarts though?
> 
> Actually yes, I should have mentioned this in my previous message.
> 
> YosemiteV3.5 is similar to YosemiteV3, which you can see here:
> 
> https://www.opencompute.org/products/423/wiwynn-yosemite-v3-server
> 
> This dts is for the BMC on the sled baseboard, and it manages the 4 slots in the
> sled. Each slot has a "Bridge Interconnect" (BIC) (an AST1030) that manages the
> slot CPU/etc. uart1 is connected to a uart on slot1's BIC, uart2 to slot2, etc.
> 
> We also have a work-in-progress QEMU model for this:
> 
> https://lore.kernel.org/qemu-devel/20220714154456.2565189-1-clg@kaod.org/
> 
> > 
> > > > > +       chosen {
> > > > > +               stdout-path = &uart5;
> > > > > +               bootargs = "console=ttyS4,57600n8 root=/dev/ram rw vmalloc=384M";
> > > > > +       };
> > >
> > > Also: if we do serial0 = &uart5, it should be console=ttyS0, not ttyS4.
> > >
> > > >
> > > > The bootargs should really come from the boot loader.
> > >
> > > What if we want to boot the kernel by itself with QEMU? It's kinda annoying to
> > > have to specify '-append "console=ttyS0,57600n8...' everytime, or to have to use
> > > a wrapper script. But, it's also a source of bugs: I realized yesterday the
> > > dts we were using here:
> > >
> > > https://github.com/facebook/openbmc-linux/blob/e26c76992e0761d9e440ff514538009384c094b4/arch/arm/boot/dts/aspeed-bmc-facebook-fby35.dts
> > >
> > > Has the wrong console setting.
> > 
> > You can encode the uart settings like
> > 
> >            stdout-path = "serial0:115200n8"
> > 
> > the rest really should be passed on the command line, not in
> > the DT shipped with the kernel.

Oh sorry, I missed this comment:

That sounds good, I'm fine with that. We should remove the bootargs then.

Thanks,
Peter

> > 
> >         Arnd