linux-kernel - Re: [PATCH 0/3] PCI/gic-v3-its: Add support for same ITS device ID for multiple PCIe devices

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Message-ID: <87v92vv5r3.wl-maz@kernel.org>
Date:   Mon, 20 Sep 2021 12:36:00 +0100
From:   Marc Zyngier <maz@...nel.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        <lokeshvutla@...com>
Subject: Re: [PATCH 0/3] PCI/gic-v3-its: Add support for same ITS device ID for multiple PCIe devices

On Mon, 20 Sep 2021 12:22:48 +0100,
Kishon Vijay Abraham I <kishon@...com> wrote:
> 
> Hi Marc,
> 
> On 20/09/21 2:44 pm, Marc Zyngier wrote:
> > On Mon, 20 Sep 2021 07:41:30 +0100,
> > Kishon Vijay Abraham I <kishon@...com> wrote:
> >>
> >> AM64 has an issue in that it doesn't trigger interrupt if the address
> >> in the *pre_its_window* is not aligned to 8-bytes (this is due to an
> >> invalid bridge configuration in HW).
> >>
> >> This means there will not be interrupts for devices with PCIe
> >> requestor ID 0x1, 0x3, 0x5..., as the address in the pre-ITS window
> >> would be 4 (1 << 2), 12 (3 << 2), 20 (5 << 2) respectively which are
> >> not aligned to 8-bytes.
> >>
> >> The DT binding has specified "msi-map-mask" using which multiple PCIe
> >> devices could be made to use the same ITS device ID.
> >>
> >> Add support in irq-gic-v3-its-pci-msi.c for such cases where multiple
> >> PCIe devices are using the same ITS device ID.
> >>
> >> Kishon Vijay Abraham I (3):
> >>   PCI: Add support in pci_walk_bus() to invoke callback matching RID
> >>   PCI: Export find_pci_root_bus()
> >>   irqchip/gic-v3-its: Include "msi-map-mask" for calculating nvecs
> >>
> >>  drivers/irqchip/irq-gic-v3-its-pci-msi.c | 21 ++++++++++++++++++++-
> >>  drivers/pci/bus.c                        | 13 +++++++++----
> >>  drivers/pci/host-bridge.c                |  3 ++-
> >>  include/linux/pci.h                      |  8 ++++++--
> >>  4 files changed, 37 insertions(+), 8 deletions(-)
> > 
> > What I don't see in this series is how you address the other part of
> > the problem, which is your reuse of the Socionext hack. Please post a
> > complete series addressing all the issues for this HW.
> 
> No additional patches are pending. Socionext configuration is used as is
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/arm64/boot/dts/ti/k3-am64-main.dtsi#n72

Hmmm. You are pretty lucky that the Socionext machine is also using a
GIC-500, and that your pre-ITS widget falls into the low 4GB...

> FWIW the issue that I address in this series is not observed with
> standalone USB cards or NVMe cards. The issue was observed when I
> tried with a multi-function PCIe card.

That's indeed what I understood of the bug.

	M.

-- 
Without deviation from the norm, progress is not possible.