linux-kernel - Re: [PATCH] PCI: shpchp: Fix probing logic inversion

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Message-ID: <20180625125204.GH2558@lahna.fi.intel.com>
Date:   Mon, 25 Jun 2018 15:52:04 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: shpchp: Fix probing logic inversion

On Thu, Jun 21, 2018 at 05:47:15PM +0100, Marc Zyngier wrote:
> Until recently, shpc_probe() would bail out pretty early in the
> absence of the SHPC capability. A logic change in the way the
> driver now checks that capability makes it go and probe the
> firmware anyway, with ugly consequences if the system is not
> ACPI based (my arm64 ThunderX is DT driven, and explodes in
> a spectacular way after getting a NULL root bridge from the
> non-existent ACPI tables...).

Could you share log from the failure? I would like to understand a bit
better where it crashes and why.

> Take this opportunity to move the call to shpchp_is_native()
> back into shpc_probe(), making it clear that a non-ACPI system
> is not expected to use this driver.

It is fine to use SHPC in non-ACPI systems. However, in ACPI systems we
should negotiate whether it is the OS or the firmware who handles it.