linux-kernel - Re: [PATCH v4 1/2] arm64: dts: lx2160a: update PCIe nodes to match rev2 silicon

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Message-ID: <Yx+XonDqmpE4KGhD@shell.armlinux.org.uk>
Date:   Mon, 12 Sep 2022 21:33:38 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Olof Johansson <olof@...om.net>
Cc:     Li Yang <leoyang.li@....com>, shawnguo@...nel.org,
        devicetree@...r.kernel.org, robh+dt@...nel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Hou Zhiqiang <Zhiqiang.Hou@....com>
Subject: Re: [PATCH v4 1/2] arm64: dts: lx2160a: update PCIe nodes to match
 rev2 silicon

On Mon, Sep 12, 2022 at 11:54:06AM -0700, Olof Johansson wrote:
> On Mon, Sep 12, 2022 at 12:05 AM Olof Johansson <olof@...om.net> wrote:
> >
> > Hi,
> >
> > On Wed, Aug 17, 2022 at 1:26 PM Li Yang <leoyang.li@....com> wrote:
> > >
> > > The original dts was created based on the non-production rev1 silicon
> > > which was only used for evaluation.  Update the PCIe nodes to align with
> > > the different controller used in production rev2 silicon.
> >
> > How can I confirm what version of silicon I have on a system?
> >
> > My non-evaluation commercially purchased system (HoneyComb LX2K) has:
> >
> > # cat /sys/bus/soc/devices/soc0/revision
> > 1.0
> >
> > And I will be really grumpy if this system stops working. It's what I
> > use to do all my maintainer work, even if that's been fairly dormant
> > this year.
> >
> > It's overall setting off red flags to update an in-place devicetree to
> > a "new revision" of silicon instead of adding a new DT for said
> > revision. 2160A has been on the market for several years, so it just
> > seems odd to all of the sudden retroactively make things
> > non-backwards-compatible.
> 
> Confirmed that this patch renders my HoneyComb unbootable -- PCIe doesn't probe.
> 
> Shawn, please revert, and be on the lookout for similar problematic
> approaches in the future. Thanks!

I think you may also need to beware of the MC firmware revision - I
seem to remember reading in the changelog notes for it that NXP
dropped support in the MC firmware for the older silicon, though I
may be misremembering. It's been a while since I really looked at
the LX2160A from the point of view of maintaining or developing
anything for it.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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