linux-kernel - Re: [PATCH v2 3/4] arm64: dts: marvell: cn9132-clearfog: fix multi-lane pci x2 and x4 ports

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Message-ID: <dedd4222-b2ba-4247-98b4-504b5c032f69@lunn.ch>
Date: Thu, 18 Sep 2025 16:09:52 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Josua Mayer <josua@...id-run.com>
Cc: Gregory Clement <gregory.clement@...tlin.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Frank Wunderlich <frank-w@...lic-files.de>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] arm64: dts: marvell: cn9132-clearfog: fix
 multi-lane pci x2 and x4 ports

On Thu, Sep 18, 2025 at 10:46:03AM +0000, Josua Mayer wrote:
> Am 12.09.25 um 00:12 schrieb Andrew Lunn:
> > On Thu, Sep 11, 2025 at 08:28:06PM +0200, Josua Mayer wrote:
> >> The mvebu-comphy driver does not currently know how to pass correct
> >> lane-count to ATF while configuring the serdes lanes.
> >>
> >> This causes the system to hard reset during reconfiguration, if a pci
> >> card is present and has established a link during bootloader.
> >>
> >> Remove the comphy handles from the respective pci nodes to avoid runtime
> >> reconfiguration, relying solely on bootloader configuration - while
> >> avoiding the hard reset.
> >>
> >> When bootloader has configured the lanes correctly, the pci ports are
> >> functional under Linux.
> > Does this require a specific bootloader? Can i use mainline grub or
> > bareboot?
> 
> In this case it means U-Boot, i.e. before one would start grub.
> 
> I am never quite sure if in this situation I should say "firmware" instead ...

What you failed to answer is my question about 'mainline'? Do i need a
specific vendor u-boot, or can i just use mainline u-boot, or mainline
bareboot.

I personally like to replace the bootloader, because the one shipped
with the board often has useful features disabled, or is old. If i do
that, will the board work? I would much prefer the kernel makes no
assumptions about the bootloader. You said:

> The mvebu-comphy driver does not currently know how to pass correct
> lane-count to ATF while configuring the serdes lanes.

Why not just teach mvebu-comphy to pass the correct line-count? That
sounds like the proper fix, and that makes the kernel independent of
the bootloader.

	Andrew