linux-kernel - Re: [PATCH 2/2] clk: mvebu: cp110 add CLK_IGNORE_UNUSED to pcie_x10, pcie_x11 & pcie

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Message-ID: <05d450d8-8df9-490f-ac53-3f45544f1c29@lunn.ch>
Date: Thu, 30 Oct 2025 16:33:40 +0100
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>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...nel.org>,
	Rabeeh Khoury <rabeeh@...id-run.com>,
	Yazan Shhady <yazan.shhady@...id-run.com>,
	Mikhail Anikin <mikhail.anikin@...id-run.com>,
	Jon Nettleton <jon@...id-run.com>,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org
Subject: Re: [PATCH 2/2] clk: mvebu: cp110 add CLK_IGNORE_UNUSED to pcie_x10,
 pcie_x11 & pcie_x4

On Thu, Oct 30, 2025 at 04:16:26PM +0100, Josua Mayer wrote:
> CP110 based platforms rely on the bootloader for pci port
> initialization.
> TF-A actively prevents non-uboot re-configuration of pci lanes, and many
> boards do not have software control over the pci card reset.
> 
> If a pci port had link at boot-time and the clock is stopped at a later
> point, the link fails and can not be recovered.
> 
> PCI controller driver probe - and by extension ownership of a driver for
> the pci clocks - may be delayed especially on large modular kernels,
> causing the clock core to start disabling unused clocks.
> 
> Add the CLK_IGNORE_UNUSED flag to the three pci port's clocks to ensure
> they are not stopped before the pci controller driver has taken
> ownership and tested for an existing link.
> 
> This fixes failed pci link detection when controller driver probes late,
> e.g. with arm64 defconfig and CONFIG_PHY_MVEBU_CP110_COMPHY=m.

Seems like a reasonable compromise, given that TF-A could be classed
as broken. This must also prevent suspend/resume powering off PCI
devices, and then reconnecting them on resume.

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew