Re: [PATCH 00/10] arm64: dts: qcom: sc8280xp: enable GICv3 ITS for PCIe

Manivannan Sadhasivam
2024-02-14T06:36:01Z

On Mon, Feb 12, 2024 at 05:50:33PM +0100, Johan Hovold wrote:
> This series addresses a few problems with the sc8280xp PCIe
> implementation.
>
> The DWC PCIe controller can either use its internal MSI controller or an
> external one such as the GICv3 ITS. Enabling the latter allows for
> assigning affinity to individual interrupts, but results in a large
> amount of Correctable Errors being logged on both the Lenovo ThinkPad
> X13s and the sc8280xp-crd reference design.
>
> It turns out that these errors are always generated,

How did you confirm this?

> but for some yet to
> be determined reason, the AER interrupts are never received when using
> the internal MSI controller, which makes the link errors harder to
> notice.
>

If you manually inject the errors using "aer-inject", are you not seeing the AER
errors with internal MSI controller as well?

> On the X13s, there is a large number of errors generated when bringing
> up the link on boot. This is related to the fact that UEFI firmware has
> already enabled the Wi-Fi PCIe link at Gen2 speed and restarting the
> link at Gen3 generates a massive amount of errors until the Wi-Fi
> firmware is restarted.
>
> A recent commit enabling ASPM on certain Qualcomm platforms introduced
> further errors when using the Wi-Fi on the X13s as well as when
> accessing the NVMe on the CRD. The exact reason for this has not yet
> been identified, but disabling ASPM L0s makes the errors go away. This
> could suggest that either the current ASPM implementation is incomplete
> or that L0s is not supported with these devices.
>

What are those "further errors" you are seeing with ASPM enabled? Are those
errors appear with GIC ITS or with internal MSI controller as well?

> Note that the X13s and CRD use the same Wi-Fi controller, but the errors
> are only generated on the X13s. The NVMe controller on my X13s does not
> support L0s so there are no issues there, unlike on the CRD which uses a
> different controller. The modem on the CRD does not generate any errors,
> but both the NVMe and modem keeps bouncing in and out of L0s/L1 also
> when not used, which could indicate that there are bigger problems with
> the ASPM implementation. I don't have a modem on my X13s so I have not
> been able to test whether L0s causes an trouble there.
>
> Enabling AER error reporting on sc8280xp could similarly also reveal
> existing problems with the related sa8295p and sa8540p platforms as they
> share the base dtsi.
>
> The last four patches, marked as RFC, adds support for disabling ASPM
> L0s in the devicetree and disables it selectively for the X13s Wi-Fi
> and CRD NVMe. If it turns out that the Qualcomm PCIe implementation is
> incomplete, we may need to disable ASPM (L0s) completely in the driver
> instead.
>

If the device is not supporting L0s, then it as to be disabled in the device,
not in the PCIe controller, no?

> Note that disabling ASPM L0s for the X13s Wi-Fi does not seem to have a
> significant impact on the power consumption
>
> The DT bindings and PCI patch are expected to go through the PCI tree,
> while Bjorn A takes the devicetree updates through the Qualcomm tree.
>

Since I took a stab at enabling the GIC ITS previously, I noticed that the NVMe
performance got a slight dip. And that was one of the reasons (apart from AER
errors) that I never submitted the patch.

Could you share the NVMe benchmark (fio) with this series?

> Johan
>
>
> Johan Hovold (10):
> dt-bindings: PCI: qcom: Allow 'required-opps'
> dt-bindings: PCI: qcom: Do not require 'msi-map-mask'
> arm64: dts: qcom: sc8280xp: add missing PCIe minimum OPP
> arm64: dts: qcom: sc8280xp-crd: limit pcie4 link speed
> arm64: dts: qcom: sc8280xp-x13s: limit pcie4 link speed
> arm64: dts: qcom: sc8280xp: enable GICv3 ITS for PCIe

Is this patch based on the version I shared with you long back? If so, I'd
expect to have some credit. If you came up with your own version, then ignore
this comment.

- Mani

> dt-bindings: PCI: qcom: Allow 'aspm-no-l0s'
> PCI: qcom: Add support for disabling ASPM L0s in devicetree
> arm64: dts: qcom: sc8280xp-crd: disable ASPM L0s for NVMe
> arm64: dts: qcom: sc8280xp-x13s: disable ASPM L0s for Wi-Fi
>
> .../devicetree/bindings/pci/qcom,pcie.yaml | 6 +++++-
> arch/arm64/boot/dts/qcom/sc8280xp-crd.dts | 4 ++++
> .../qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 3 +++
> arch/arm64/boot/dts/qcom/sc8280xp.dtsi | 17 +++++++++++++++-
> drivers/pci/controller/dwc/pcie-qcom.c | 20 +++++++++++++++++++
> 5 files changed, 48 insertions(+), 2 deletions(-)
>
> --
> 2.43.0
>

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