Re: [PATCH v5 08/12] PCI: imx6: Config look up table(LUT) to support MSI ITS and IOMMU for i.MX95

From: Frank Li <Frank.li@nxp.com>
To: Marc Zyngier <maz@kernel.org>
Cc: "Robin Murphy" <robin.murphy@arm.com>,
	"Bjorn Helgaas" <helgaas@kernel.org>,
	"Richard Zhu" <hongxing.zhu@nxp.com>,
	"Lucas Stach" <l.stach@pengutronix.de>,
	"Lorenzo Pieralisi" <lpieralisi@kernel.org>,
	"Krzysztof Wilczyński" <kw@linux.com>,
	"Rob Herring" <robh@kernel.org>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Shawn Guo" <shawnguo@kernel.org>,
	"Sascha Hauer" <s.hauer@pengutronix.de>,
	"Pengutronix Kernel Team" <kernel@pengutronix.de>,
	"Fabio Estevam" <festevam@gmail.com>,
	"NXP Linux Team" <linux-imx@nxp.com>,
	"Philipp Zabel" <p.zabel@pengutronix.de>,
	"Liam Girdwood" <lgirdwood@gmail.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Manivannan Sadhasivam" <manivannan.sadhasivam@linaro.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	linux-pci@vger.kernel.org, imx@lists.linux.dev,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, bpf@vger.kernel.org,
	devicetree@vger.kernel.org, "Will Deacon" <will@kernel.org>,
	"Joerg Roedel" <joro@8bytes.org>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Alyssa Rosenzweig" <alyssa@rosenzweig.io>
Subject: Re: [PATCH v5 08/12] PCI: imx6: Config look up table(LUT) to support MSI ITS and IOMMU for i.MX95
Date: Tue, 4 Jun 2024 11:47:58 -0400	[thread overview]
Message-ID: <Zl83LikwgjpHUZc7@lizhi-Precision-Tower-5810> (raw)
In-Reply-To: <86cyowlog0.wl-maz@kernel.org>

On Tue, Jun 04, 2024 at 04:25:51PM +0100, Marc Zyngier wrote:
> On Mon, 03 Jun 2024 22:04:23 +0100,
> Frank Li <Frank.li@nxp.com> wrote:
> > 
> > iommu may share one stream id for multi-devices. but ITS MSI can't. each
> > device's MSI index start from 0. It needs difference stream id for each
> > device.
> 
> That's not quite true. We go through all sort of hoops to find about
> device aliasing on PCI and allow devices that translate into the same
> DID to get MSIs.

Could you please point me the code location? I remember I met error when I
try to enable MSI for EP support one year ago.

https://lore.kernel.org/imx/20221124055036.1630573-1-Frank.Li@nxp.com/

I remember that it is failure try to allocate more irqs with the same DID. 

Frank

> 
> Of course, just like the IOMMU, you lose any form of isolation, but
> you get what you pay for.

Anyways, if there are one quirk in PCI system, bridge driver can detect
PCI devices add/remove. it will be better if assign stream ID as need,
compared with static allocate.

> 
> 	M.
> 
> -- 
> Without deviation from the norm, progress is not possible.

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