RE: [ARM SMMU] Dynamic StreamID allocation

[Pankaj Bansal <pankaj.bansal@nxp.com>]

Correction: we use ARM SMMU-500.
Corresponding bindings are : https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindings/iommu/arm,smmu.txt#L49

The #iommu-cells is 1 in our SOC: https://elixir.bootlin.com/linux/latest/source/arch/arm64/boot/dts/freescale/fsl-lx2160a.dtsi#L693

Regards,
Pankaj Bansal

> -----Original Message-----
> From: Pankaj Bansal
> Sent: Friday, 10 May, 2019 06:04 PM
> To: Will Deacon <will.deacon@arm.com>; Robin Murphy
> <robin.murphy@arm.com>; Joerg Roedel <joro@8bytes.org>
> Cc: linux-arm-kernel@lists.infradead.org; iommu@lists.linux-foundation.org;
> Varun Sethi <V.Sethi@nxp.com>; Nipun Gupta <nipun.gupta@nxp.com>
> Subject: [ARM SMMU] Dynamic StreamID allocation
> 
> Hi Will/Robin/Joerg,
> 
> I am s/w engineer from NXP India Pvt. Ltd.
> We are using SMMU-V3 in one of NXP SOC.
> I have a question about the SMMU Stream ID allocation in linux.
> 
> Right now the Stream IDs allocated to a device are mapped via device tree to
> the device.
> https://elixir.bootlin.com/linux/latest/source/Documentation/devicetree/bindin
> gs/iommu/arm,smmu-v3.txt#L39
> 
> As the device tree is passed from bootloader to linux, we detect all the stream
> IDs needed by a device in bootloader and add their IDs in respective device
> nodes.
> For each PCIE Endpoint (a unique BDF (Bus Device Function)) on PCIE bus, we are
> assigning a unique Stream ID in bootloader.
> 
> However, this poses an issue with PCIE hot plug.
> If we plug in a pcie device while linux is running, a unique BDF is assigned to the
> device, for which there is no stream ID in device tree.
> 
> How can this problem be solved in linux?
> 
> Is there a way to assign (and revoke) stream IDs at run time?
> 
> Regards,
> Pankaj Bansal

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