linux-kernel - Re: [PATCH] arm64: dts: qcom: qcs6490-rb3gen2: Add PCIe nodes

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Message-ID: <20241012124334.4gsspgtuud4uudop@thinkpad>
Date: Sat, 12 Oct 2024 18:13:34 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Krishna Chaitanya Chundru <quic_krichai@...cinc.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	quic_vbadigan@...cinc.com, quic_ramkri@...cinc.com,
	quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
	quic_parass@...cinc.com
Subject: Re: [PATCH] arm64: dts: qcom: qcs6490-rb3gen2: Add PCIe nodes

On Fri, Oct 11, 2024 at 05:24:29PM +0530, Krishna Chaitanya Chundru wrote:

[...]

> > > The logic here is that the fixed endpoints in the switch will get an unique SID
> > > and the devices getting attached to slots will share the same SID of the bus
> > > (this is the usual case with all Qcom SoCs).
> > > 
> > > But I guess we would need 'iommu-map-mask' as well. Hope this addresses your
> > > concern.
> > 
> > Yes, thank you!
> > 
> Hi dimitry & mani,
> 
> This particular board variant doesn't expose any open slots to connect
> a different endpoints like another switch(which might have BDF unknown
> to us) so static table should be fine for this board variant.
> 
> I tries to add iommu-map-mask property, the issue with that property is
> that the driver is applying the mask to the bdf before searching for the
> entry in the table. If I use a mask value which satisfies all the
> entries in the table ( mask as 0x718) and if a new bdf is enumerated
> lets say 0x600 due to mask 0x718 its value is again 0x600 only.
> 
> Can we skip iommu-map-mask property and use only static table for this
> board as we know this board doesn't expose any open slots.
> 

Hmm, I was not aware that it doesn't have open slots. Fine with me then.

- Mani

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