Hi Ard,
[+ devicetree@]
On Fri, Apr 14, 2017 at 01:43:15PM +0100, Ard Biesheuvel wrote:
> DT nodes may have a status property, and if they do, such nodes should
> only be considered present if the status property is set to 'okay'.
>
> Currently, we call the init function of IOMMUs described by the device
> tree without taking this into account, which may result in the output
> below on systems where some SMMUs may be legally disabled.
>
> Failed to initialise IOMMU /smb/smmu@e0200000
> Failed to initialise IOMMU /smb/smmu@e0c00000
> arm-smmu e0a00000.smmu: probing hardware configuration...
> arm-smmu e0a00000.smmu: SMMUv1 with:
> arm-smmu e0a00000.smmu: stage 2 translation
> arm-smmu e0a00000.smmu: coherent table walk
> arm-smmu e0a00000.smmu: stream matching with 32 register groups, mask 0x7fff
> arm-smmu e0a00000.smmu: 8 context banks (8 stage-2 only)
> arm-smmu e0a00000.smmu: Supported page sizes: 0x60211000
> arm-smmu e0a00000.smmu: Stage-2: 40-bit IPA -> 40-bit PA
> Failed to initialise IOMMU /smb/smmu@e0600000
> Failed to initialise IOMMU /smb/smmu@e0800000
>
> Since this is not an error condition, only call the init function if
> the device is enabled, which also inhibits the spurious error messages.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> ---
> drivers/iommu/of_iommu.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/of_iommu.c b/drivers/iommu/of_iommu.c
> index 2683e9fc0dcf..2dd1206e6c0d 100644
> --- a/drivers/iommu/of_iommu.c
> +++ b/drivers/iommu/of_iommu.c
> @@ -183,7 +183,7 @@ static int __init of_iommu_init(void)
> for_each_matching_node_and_match(np, matches, &match) {
> const of_iommu_init_fn init_fn = match->data;
>
> - if (init_fn(np))
> + if (of_device_is_available(np) && init_fn(np))
> pr_err("Failed to initialise IOMMU %s\n",
> of_node_full_name(np));
> }
Is there a definition of what status = "disabled" is supposed to mean for an
IOMMU? For example, that could mean that the firmware has pre-programmed the
SMMU with particular translations or memory attributes (a bit like the
CCA=1, CPM=1, DACS=0 case in ACPI IORT), or even disabled DMA traffic
altogether.
So I think we'd need an update to the generic IOMMU binding text to say
exactly what the semantics are supposed to be here.
Will
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