linux-kernel - Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating PCI devices

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Date:   Thu, 2 Sep 2021 14:51:43 +0200
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Wang Xingang <wangxingang5@...wei.com>,
        Rob Herring <robh@...nel.org>, Will Deacon <will@...nel.org>,
        joro@...tes.org, helgaas@...nel.org,
        Rob Herring <robh+dt@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        iommu@...ts.linux-foundation.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-pci@...r.kernel.org, xieyingtai@...wei.com,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux-Next Mailing List <linux-next@...r.kernel.org>
Subject: Re: [PATCH v4] iommu/of: Fix pci_request_acs() before enumerating PCI devices

On Wed, 1 Sept 2021 at 11:58, Robin Murphy <robin.murphy@....com> wrote:
>
> On 2021-09-01 09:59, Marek Szyprowski wrote:
> > On 21.05.2021 05:03, Wang Xingang wrote:
> >> From: Xingang Wang <wangxingang5@...wei.com>
> >>
> >> When booting with devicetree, the pci_request_acs() is called after the
> >> enumeration and initialization of PCI devices, thus the ACS is not
> >> enabled. And ACS should be enabled when IOMMU is detected for the
> >> PCI host bridge, so add check for IOMMU before probe of PCI host and call
> >> pci_request_acs() to make sure ACS will be enabled when enumerating PCI
> >> devices.
> >>
> >> Fixes: 6bf6c24720d33 ("iommu/of: Request ACS from the PCI core when
> >> configuring IOMMU linkage")
> >> Signed-off-by: Xingang Wang <wangxingang5@...wei.com>
> >
> > This patch landed in linux-next as commit 57a4ab1584e6 ("iommu/of: Fix
> > pci_request_acs() before enumerating PCI devices"). Sadly it breaks PCI
> > operation on ARM Juno R1 board (arch/arm64/boot/dts/arm/juno-r1.dts). It

We've seen this on ARM Juno R2 boards too in the Linaro testfarm.

The problem is that the device can't get the "SATA link up" while booting.

see https://lkft.validation.linaro.org/scheduler/job/3416767#L577

When reverting this patch we are able to see the "SATA link up".

Cheers,
Anders