Received-SPF: pass (google.com: domain of linux-kernel+bounces-58387-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:40f1:3f00::1 as permitted sender) client-ip=2604:1380:40f1:3f00::1;
Message-ID: <9654146ac849bb00faf2fe963d3da94ad65003b8.camel@linux.intel.com>
Subject: Re: [PATCH v2 1/2] PCI: Disable D3cold on Asus B1400 PCI-NVMe bridge
From: "David E. Box" <david.e.box@linux.intel.com>
Reply-To: david.e.box@linux.intel.com
To: Daniel Drake <drake@endlessos.org>, Bjorn Helgaas <helgaas@kernel.org>
Cc: tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, 
 dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, 
 linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
 bhelgaas@google.com,  mario.limonciello@amd.com, rafael@kernel.org,
 lenb@kernel.org,  linux-acpi@vger.kernel.org, linux@endlessos.org
Date: Thu, 08 Feb 2024 08:57:12 -0800
In-Reply-To: <CAD8Lp44-8WhPyOrd2dCWyG3rRuCqzJ-aZCH6b1r0kyhfcXJ8xg@mail.gmail.com>
References: <20240207084452.9597-1-drake@endlessos.org>
	 <20240207200538.GA912749@bhelgaas>
	 <CAD8Lp47DjuAAxqwt+yKD22UNMyvqE00x0u+JeM74KO2OC+Otrg@mail.gmail.com>
	 <CAD8Lp44-8WhPyOrd2dCWyG3rRuCqzJ-aZCH6b1r0kyhfcXJ8xg@mail.gmail.com>
Organization: David E. Box
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.4-0ubuntu2 
Precedence: bulk
MIME-Version: 1.0

On Thu, 2024-02-08 at 10:52 +0100, Daniel Drake wrote:
> On Thu, Feb 8, 2024 at 9:37=E2=80=AFAM Daniel Drake <drake@endlessos.org>=
 wrote:
> > > What would be the downside of skipping the DMI table and calling
> > > pci_d3cold_disable() always?=C2=A0 If this truly is a Root Port defec=
t, it
> > > should affect all platforms with this device, and what's the benefit
> > > of relying on BIOS to use StorageD3Enable to avoid the defect?
> >=20
> > I had more assumed that it was a platform-specific DSDT bug, in that
> > PEG0.PXP._OFF is doing something that PEG0.PXP._ON is unable to
> > recover from, and that other platforms might handle the suspend/resume
> > of this root port more correctly. Not sure if it is reasonable to
> > assume that all other platforms on the same chipset have the same bug
> > (if that's what this is).

This does look like a firmware bug. We've had reports of D3cold support mis=
sing
when running in non-VMD mode on systems that were designed with VMD for Win=
dows.
These issues have been caught and addressed by OEMs during enabling of Linu=
x
systems. Does D3cold work in VMD mode?

David

>=20
> Just realised my main workstation (Dell XPS) has the same chipset.
>=20
> The Dell ACPI table has the exact same suspect-buggy function, which
> the affected Asus system calls from PEG0.PXP._OFF:
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Method (DL23, 0, Serialized)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 L23E =
=3D One
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Sleep =
(0x10)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Local0=
 =3D Zero
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 While =
(L23E)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 If ((Local0 > 0x04))
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 {
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 Break
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 }
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 Sleep (0x10)
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=
=C2=A0=C2=A0=C2=A0 Local0++
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 }
>=20
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 SCB0 =
=3D One
> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 }
>=20
> (the "L23E =3D One" line is the one that writes a value to config offset
> 0xe2, if you comment out this line then everything works)
>=20
> However, on the Dell XPS system, nothing calls DL23() i.e. it is dead cod=
e.
>=20
> Comparing side by side:
> Asus root port (PC00.PEG0) has the PXP power resource which gets
> powered down during D3cold transition as it becomes unused. Dell root
> port has no power resources (no _PR0).
> Asus NVM device sitting under that root port (PC00.PEG0.PEGP) has
> no-op _PS3 method, but Dell does not have _PS3. This means that Dell
> doesn't attempt D3cold on NVMe nor the parent root port during suspend
> (both go to D3hot only).
>=20
> Let me know if you have any ideas for other useful comparative experiment=
s.
> Daniel