Re: [PATCH RESEND] iommu/of: Fix pci_request_acs() before enumerating PCI devices

[Pavan Kondeti]

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@xxxxxxxxxx>
> > 
> > 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@xxxxxxxxxx>
> > Signed-off-by: Pavankumar Kondeti <quic_pkondeti@xxxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxx/
> 
> 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