linux-kernel - Re: [PATCH RESEND] iommu/of: Fix pci_request

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Message-ID: <be01d3e0-3c3a-46ec-ae68-df1cf88415de@quicinc.com>
Date: Thu, 7 Nov 2024 14:12:46 +0530
From: Pavan Kondeti <quic_pkondeti@...cinc.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC: Pavankumar Kondeti <quic_pkondeti@...cinc.com>,
        Joerg Roedel
	<joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy
	<robin.murphy@....com>,
        Bjorn Helgaas <bhelgaas@...gle.com>, Joerg Roedel
	<jroedel@...e.de>,
        Rob Herring <robh@...nel.org>,
        Marek Szyprowski
	<m.szyprowski@...sung.com>,
        Anders Roxell <anders.roxell@...aro.org>, <iommu@...ts.linux.dev>,
        <linux-kernel@...r.kernel.org>, <linux-pci@...r.kernel.org>,
        Xingang Wang <wangxingang5@...wei.com>
Subject: Re: [PATCH RESEND] iommu/of: Fix pci_request_acs() before
 enumerating PCI devices

On Thu, Nov 07, 2024 at 09:17:44AM +0100, Greg Kroah-Hartman wrote:
> On Thu, Nov 07, 2024 at 01:29:15PM +0530, Pavankumar Kondeti 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>
> > Signed-off-by: Pavankumar Kondeti <quic_pkondeti@...cinc.com>
> > ---
> > Earlier this patch made it to linux-next but got dropped later as it
> > broke PCI on ARM Juno R1 board. AFAICT, this issue is never root caused,
> > so resending this patch to get attention again.
> > 
> > https://lore.kernel.org/all/1621566204-37456-1-git-send-email-wangxingang5@huawei.com/
> 
> Please don't resend known-broken patches.  Please fix them up before
> resending, otherwise we will just ignore this one as well as obviously
> we can not take such a thing (nor should you want us to.)
> 

Thanks Greg for taking a look.

AFAICT, there is nothing wrong with the patch (It was Ackd before). The
root cause of the breakage on Juno ARM board is not identified. I resent
the patch to get the attention from people who reported this problem few
years back. I am *hoping* that they might have fixed the issue on their
side.

Thanks,
Pavan