does dtb not support pci acs enable?

[Bjorn Helgaas]

On Thu, Aug 01, 2024 at 06:43:59PM -0500, Bjorn Helgaas wrote:
> [+cc ARM, IOMMU folks; I don't know the answer, but maybe they do]

[+cc Vidya, Pavan, also see this recent thread:
https://lore.kernel.org/r/PH8PR12MB667446D4A4CAD6E0A2F488B5B83F2@PH8PR12MB6674.namprd12.prod.outlook.com]

> On Fri, Jul 19, 2024 at 11:01:11PM +0800, steven wrote:
> > Hello,
> > 
> > I am a new person in PCI, I am trying to do something for iommu
> > group on arm64 platform, I found if I boot the linux (5.10 kernel)
> > kernel using UEFI + ACPI, it will work correctly. But if I boot it
> > using UEFI + DTB, the iommu group not work, only one group present.
> > 
> > I read the code, found that pci_acs_enable is set to 1 during
> > acpi_init, but I can not find any code for dtb booting, so it will
> > return "disable_acs_redir " during call pci_enable_acs. 
> >
> > static void pci_enable_acs(struct pci_dev *dev)
> > {
> >     if (!pci_acs_enable)
> >         goto disable_acs_redir;
> > 
> >     if (!pci_dev_specific_enable_acs(dev))
> >         goto disable_acs_redir;
> > 
> >     pci_std_enable_acs(dev);
> > 
> > 
> > 
> > 
> > SO, is it not support in dtb?
> >