From: Jason Gunthorpe <jgg@ziepe.ca>
To: Peng Fan <peng.fan@oss.nxp.com>
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
Will Deacon <will@kernel.org>,
Robin Murphy <robin.murphy@arm.com>, Frank Li <frank.li@nxp.com>,
"Joerg Roedel (AMD)" <joro@8bytes.org>,
Jean-Philippe Brucker <jpb@kernel.org>,
linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, Peng Fan <peng.fan@nxp.com>
Subject: Re: [PATCH RFC 0/4] iommu/arm-smmu-v3: Support shared Stream IDs
Date: Fri, 18 Sep 2026 09:11:32 -0300 [thread overview]
Message-ID: <20260918121132.GA11599@ziepe.ca> (raw)
In-Reply-To: <aq0lEk56qRi93geW@shlinux89>
On Fri, Sep 18, 2026 at 07:48:34PM +0800, Peng Fan wrote:
> However, the DMA channel case was just one example - the shared-SID
> need exists independently of it. Our SoC (i.MX95) has only 64 SIDs
> total, serving MMC, SD, NET, PCI, DMA, NPU, DSP, DISPLAY and more.
> Some of these are genuinely separate platform devices (distinct DT
> nodes, distinct drivers) that share a SID by hardware design because
> the SID space is exhausted.
>
> That cross-IP case cannot be solved by DT restructuring - the devices
> really are separate. Would you be open to reviewing the shared-SID
> SMMU support (patches 1-4) on that basis, independent of the DMA
> channel question?
I think you should revise your commit message/cover letter to focus on
something that is not a DT abuse and try again
IIRC Robin said the SID aliasing was a PITA on SMMUv2 so it
really needs to have a strong reason.
Jason
next prev parent reply other threads:[~2026-09-18 12:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 15:12 [PATCH RFC 0/4] iommu/arm-smmu-v3: Support shared Stream IDs Peng Fan (OSS)
2026-09-16 15:12 ` [PATCH RFC 1/4] iommu/arm-smmu-v3: Convert streams from RB tree to XArray Peng Fan (OSS)
2026-09-16 15:12 ` [PATCH RFC 2/4] iommu/arm-smmu-v3: Support shared SIDs in insert/remove_master Peng Fan (OSS)
2026-09-16 15:12 ` [PATCH RFC 3/4] iommu/arm-smmu-v3: Group aliasing devices into the same IOMMU group Peng Fan (OSS)
2026-09-16 15:12 ` [PATCH RFC 4/4] iommu/arm-smmu-v3: Wire up shared-SID STE ordering and feature gating Peng Fan (OSS)
2026-09-16 16:10 ` [PATCH RFC 0/4] iommu/arm-smmu-v3: Support shared Stream IDs Jason Gunthorpe
2026-09-17 1:33 ` Peng Fan
2026-09-17 14:48 ` Jason Gunthorpe
2026-09-18 11:48 ` Peng Fan
2026-09-18 12:11 ` Jason Gunthorpe [this message]
2026-09-18 13:41 ` Peng Fan
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