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Date:   Fri, 15 Jul 2022 09:29:45 +0100
From:   Matthew Garrett <mjg59@srcf.ucam.org>
To:     Manyi Li <limanyi@uniontech.com>
Cc:     Kai-Heng Feng <kai.heng.feng@canonical.com>,
        Bjorn Helgaas <helgaas@kernel.org>, bhelgaas@google.com,
        refactormyself@gmail.com, kw@linux.com, rajatja@google.com,
        linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
        Vidya Sagar <vidyas@nvidia.com>, rafael@kernel.org
Subject: Re: [PATCH] PCI/ASPM: Should not report ASPM support to BIOS if FADT
 indicates ASPM is unsupported
Message-ID: <20220715082945.GA10661@srcf.ucam.org>
References: <20220713112612.6935-1-limanyi@uniontech.com>
 <20220713182852.GA841582@bhelgaas>
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On Fri, Jul 15, 2022 at 03:40:36PM +0800, Manyi Li wrote:

> Please see the details of this issus:
> https://bugzilla.kernel.org/show_bug.cgi?id=216245

Hmm. The only case where changing aspm_support_enabled to false should 
matter is in pcie_aspm_init_link_state(), where it looks like we'll 
potentially rewrite some registers even if aspm_disabled is true. I 
think in theory we shouldn't actually modify anything as a result, and 
the lspcis from the bug don't show any ASPM values having changed, but I 
don't trust Realtek hardware in the general case so maybe it gets upset 
here? If the proposed patch is to just set aspm_support_enabled to false 
when we see the FADT bit set then I think this is fine.