linux-kernel - Re: [PATCH] pcie: Add quirk for the Arm Neoverse N1SDP platform

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Date:   Mon, 9 Dec 2019 16:26:46 +0000
From:   Will Deacon <will@...nel.org>
To:     Andre Przywara <andre.przywara@....com>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Andrew Murray <andrew.murray@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH] pcie: Add quirk for the Arm Neoverse N1SDP platform

On Mon, Dec 09, 2019 at 04:06:38PM +0000, Andre Przywara wrote:
> From: Deepak Pandey <Deepak.Pandey@....com>
> 
> The Arm N1SDP SoC suffers from some PCIe integration issues, most
> prominently config space accesses to not existing BDFs being answered
> with a bus abort, resulting in an SError.

"Do as I say, not as I do"?

> To mitigate this, the firmware scans the bus before boot (catching the
> SErrors) and creates a table with valid BDFs, which acts as a filter for
> Linux' config space accesses.
> 
> Add code consulting the table as an ACPI PCIe quirk, also register the
> corresponding device tree based description of the host controller.
> Also fix the other two minor issues on the way, namely not being fully
> ECAM compliant and config space accesses being restricted to 32-bit
> accesses only.
> 
> This allows the Arm Neoverse N1SDP board to boot Linux without crashing
> and to access *any* devices (there are no platform devices except UART).
> 
> Signed-off-by: Deepak Pandey <Deepak.Pandey@....com>
> [Sudipto: extend to cover the CCIX root port as well]
> Signed-off-by: Sudipto Paul <sudipto.paul@....com>
> [Andre: fix coding style issues, rewrite some parts, add DT support]
> Signed-off-by: Andre Przywara <andre.przywara@....com>
> ---
>  arch/arm64/configs/defconfig        |   1 +
>  drivers/acpi/pci_mcfg.c             |   7 +
>  drivers/pci/controller/Kconfig      |  11 ++
>  drivers/pci/controller/Makefile     |   1 +
>  drivers/pci/controller/pcie-n1sdp.c | 196 ++++++++++++++++++++++++++++
>  include/linux/pci-ecam.h            |   2 +
>  6 files changed, 218 insertions(+)
>  create mode 100644 drivers/pci/controller/pcie-n1sdp.c

Where can I buy one of these? They're "unreleased" according to:

https://community.arm.com/developer/tools-software/oss-platforms/w/docs/440/neoverse-n1-sdp

and I don't think we should wreck upstream because of a platform that
doesn't exist.

Will