On Tue, Mar 6, 2018 at 5:11 PM, Robin Murphy <robin.mur...@arm.com> wrote:
> On 06/03/18 04:59, Jitendra Bhivare wrote:
>
>> Certain regions in IO virtual address space may need to be reserved to be
>> not used for devices configured behind IOMMU.
>>
>> Add documentation of the property to allow such regions to be specified in
>> DT to be reserved using IOMMU_RESV_RESERVED type.
>>
>
> That sounds like software policy; DT is for describing hardware.
It is to describe the holes in address space for which hardware can't
provide mappings.
>
>
> Reviewed-by: Ray Jui <ray....@broadcom.com>
>> Reviewed-by: Vikram Prakash <vikram.prak...@broadcom.com>
>> Reviewed-by: Scott Branden <scott.bran...@broadcom.com>
>> Signed-off-by: Jitendra Bhivare <jitendra.bhiv...@broadcom.com>
>> ---
>> Documentation/devicetree/bindings/iommu/iommu.txt | 17
>> +++++++++++++++++
>> 1 file changed, 17 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/iommu/iommu.txt
>> b/Documentation/devicetree/bindings/iommu/iommu.txt
>> index 5a8b462..5a58ef2 100644
>> --- a/Documentation/devicetree/bindings/iommu/iommu.txt
>> +++ b/Documentation/devicetree/bindings/iommu/iommu.txt
>> @@ -98,6 +98,20 @@ requirements of that use-case haven't been fully
>> determined yet. Implementing
>> this is therefore not recommended without further discussion and
>> extension of
>> this binding.
>> +Optional properties:
>> +--------------------
>> +- reserved-dma-region: This specifies DMA region to be reserved with
>> specific
>> + prot in IOVA space. It is in tuples of (busno,prot,bus_addr,size).
>>
>
> What do busno and prot actually mean, and what are valid values for them?
busno was part of initial commit 4e0ee78f in implementation of
of_get_dma_window.
I am not sure what was the use of it in Powerpc. Similar implementation can
be seen
in of_parse_dma_window.
prot is access permission flags for the region for reserving in SW.This I
will remove.
>
>
> Robin.
>
>
> +- #region-address-cells: specifies number of cells needed to encode
>> bus_addr
>> +
>> +- #region-size-cells: specifies number of cells needed to encode size
>> +
>> +Notes:
>> +======
>> +This can be applied to IOMMU master node or to children (such as PCI host
>> +bridges) on the bus behind IOMMU.
>> +
>> Examples:
>> =========
>> @@ -173,6 +187,9 @@ Multiple-master IOMMU with configurable DMA window:
>> * master (i.e. the I/O virtual address space).
>> */
>> #iommu-cells = <4>;
>> + #region-address-cells = <2>;
>> + #region-size-cells = <2>;
>> + reserved-dma-region = <0x0 0x0 0x04 0x0 0x04 0x0>;
>> };
>> master {
>>
>>
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