Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <17b05a72d2db1074cef9d5e9f85b347850f171d5.camel@linux.intel.com>
Subject: Re: [PATCH V8 0/4] PCI: vmd: Enable PCIe ASPM and LTR on select
 hardware
From:   "David E. Box" <david.e.box@linux.intel.com>
Reply-To: david.e.box@linux.intel.com
To:     You-Sheng Yang <vicamo.yang@canonical.com>
Cc:     michael.a.bottini@intel.com, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, me@adhityamohan.in,
        rafael@kernel.org, hch@infradead.org, robh@kernel.org,
        bhelgaas@google.com, kw@linux.com, lorenzo.pieralisi@arm.com,
        nirmal.patel@linux.intel.com, jonathan.derrick@linux.dev
Date:   Wed, 23 Nov 2022 08:09:48 -0800
In-Reply-To: <5c766840-e092-45ea-0664-7bbdb78b933a@canonical.com>
References: <20221103021822.308586-1-david.e.box@linux.intel.com>
         <5c766840-e092-45ea-0664-7bbdb78b933a@canonical.com>
Organization: David E. Box
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
User-Agent: Evolution 3.44.4-0ubuntu1 
MIME-Version: 1.0
Precedence: bulk

Hi You-Sheng,

On Wed, 2022-11-23 at 18:27 +0800, You-Sheng Yang wrote:
> Hi David,
>=20
> On 11/3/22 10:18, David E. Box wrote:
> > This series adds a work around for enabling PCIe ASPM and for setting P=
CIe
> > LTR values on VMD reserved root ports on select platforms. While
> > configuration of these capabilities is usually done by BIOS, on these
> > platforms these capabilities will not be configured because the ports a=
re
> > not visible to BIOS. This was part of an initial design that expected t=
he
> > driver to completely handle the ports, including power management. Howe=
ver
> > on Linux those ports are still managed by the PCIe core, which has the
> > expectation that they adhere to device standards including BIOS
> > configuration, leading to this problem.
> >=20
> > The target platforms are Tiger Lake, Alder Lake, and Raptor Lake though=
 the
> > latter has already implemented support for configuring the LTR values.
> > Meteor Lake is expected add BIOS ASPM support, eliminating the future n=
eed
> > for this work around.
>=20
>=20
> It appears to me that this patch series works only on Tiger Lake. We=20
> have tried to revert our current work-arounds in Ubuntu kernels=20
> generic-5.15/oem-5.17/oem-6.0/unstable-6.1 and apply this series, the=20
> prebuilt kernels can be found in:
>=20
> =C2=A0=C2=A0 https://launchpad.net/~vicamo/+archive/ubuntu/ppa-1996620
>=20
> However, only TGL can still enter PC10 as before.
>=20
>=20
> ADL-M, RPL platforms will stay in PC3 with vmd LTR set, but ASPM=20
> disabled.

For the patch to work BIOS must allow the OS to control ASPM. If this is no=
t the
case then you will see the message "ACPI FADT declares the system doesn't
support PCIe ASPM, so disable it". Please check for this on the systems tha=
t
don't work. If so the only option is a BIOS change to enable it.

David

>  i915 RC6 blocked, too:
>=20
> $ sudo cat /sys/kernel/debug/dri/
>=20
> 0/i915_dmc_info
> ...
> DC3CO count: 0
> DC3 -> DC5 count: 100
> DC5 -> DC6 count: 0
>=20
>=20
> > Note, the driver programs the LTRs because BIOS would also normally do =
this
> > for devices that do not set them by default. Without this, SoC power
> > management would be blocked on those platform. This SoC specific value =
is
> > the maximum latency required to allow the SoC to enter the deepest powe=
r
> > state.
> >=20
> > This patch addresses the following open bugzillas on VMD enabled laptop=
s
> > that cannot enter low power states.
> >=20
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D212355
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D215063
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D213717
> >=20
> > David E. Box (3):
> > =C2=A0=C2=A0 PCI: vmd: Use PCI_VDEVICE in device list
> > =C2=A0=C2=A0 PCI: vmd: Create feature grouping for client products
> > =C2=A0=C2=A0 PCI: vmd: Add quirk to configure PCIe ASPM and LTR
> >=20
> > Michael Bottini (1):
> > =C2=A0=C2=A0 PCI/ASPM: Add pci_enable_link_state()
> >=20
> > =C2=A0 drivers/pci/controller/vmd.c | 96 ++++++++++++++++++++++++++----=
------
> > =C2=A0 drivers/pci/pcie/aspm.c=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 | 54 +++++=
+++++++++++++++
> > =C2=A0 include/linux/pci.h=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=
=A0=C2=A0 |=C2=A0 7 +++
> > =C2=A0 3 files changed, 131 insertions(+), 26 deletions(-)
> >=20
> >=20
> > base-commit: 247f34f7b80357943234f93f247a1ae6b6c3a740
>=20
>=20
> Regards,
> You-Sheng Yang
>=20