linux-kernel - Re: [PATCH 3/3] arm64: dts: qcom: sm8450: Use GIC-ITS for PCIe0 and PCIe1

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Message-ID: <20221220103400.GB38609@thinkpad>
Date:   Tue, 20 Dec 2022 16:04:00 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     andersson@...nel.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, bhelgaas@...gle.com,
        konrad.dybcio@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] arm64: dts: qcom: sm8450: Use GIC-ITS for PCIe0 and
 PCIe1

On Mon, Dec 19, 2022 at 11:46:03PM +0200, Dmitry Baryshkov wrote:
> On 19/12/2022 21:14, Manivannan Sadhasivam wrote:
> > Both PCIe0 and PCIe1 controllers are capable of receiving MSIs from
> > endpoint devices using GIC-ITS MSI controller. Add support for it.
> > 
> > Currently, BDF (0:0.0) and BDF (1:0.0) are enabled and with the
> > msi-map-mask of 0xff00, all the 32 devices under these two busses can
> > share the same Device ID.
> > 
> > The GIC-ITS MSI implementation provides an advantage over internal MSI
> > implementation using Locality-specific Peripheral Interrupts (LPI) that
> > would allow MSIs to be targeted for each CPU core.
> > 
> > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
> > ---
> >   arch/arm64/boot/dts/qcom/sm8450.dtsi | 12 ++++++------
> >   1 file changed, 6 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/arm64/boot/dts/qcom/sm8450.dtsi b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> > index 570475040d95..276ceba4c247 100644
> > --- a/arch/arm64/boot/dts/qcom/sm8450.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sm8450.dtsi
> > @@ -1733,9 +1733,9 @@ pcie0: pci@...0000 {
> >   			ranges = <0x01000000 0x0 0x60200000 0 0x60200000 0x0 0x100000>,
> >   				 <0x02000000 0x0 0x60300000 0 0x60300000 0x0 0x3d00000>;
> > -			interrupts = <GIC_SPI 141 IRQ_TYPE_LEVEL_HIGH>;
> > -			interrupt-names = "msi";
> > -			#interrupt-cells = <1>;
> > +			msi-map = <0x0 &gic_its 0x5980 0x1>,
> > +				  <0x100 &gic_its 0x5981 0x1>;
> 
> Does ITS support handling more than one MSI interrupt per device? Otherwise
> it might be better to switch to multi-MSI scheme using SPI interrupts.
> 

Yes, it does support multiple MSIs from endpoints. I've verified it using the
MHI Endpoint device.

> > +			msi-map-mask = <0xff00>;
> >   			interrupt-map-mask = <0 0 0 0x7>;
> >   			interrupt-map = <0 0 0 1 &intc 0 0 0 149 IRQ_TYPE_LEVEL_HIGH>, /* int_a */
> >   					<0 0 0 2 &intc 0 0 0 150 IRQ_TYPE_LEVEL_HIGH>, /* int_b */
> > @@ -1842,9 +1842,9 @@ pcie1: pci@...8000 {
> >   			ranges = <0x01000000 0x0 0x40200000 0 0x40200000 0x0 0x100000>,
> >   				 <0x02000000 0x0 0x40300000 0 0x40300000 0x0 0x1fd00000>;
> > -			interrupts = <GIC_SPI 307 IRQ_TYPE_LEVEL_HIGH>;
> > -			interrupt-names = "msi";
> > -			#interrupt-cells = <1>;
> > +			msi-map = <0x0 &gic_its 0x5a01 0x1>,
> > +				  <0x100 &gic_its 0x5a00 0x1>;
> 
> Are you sure that the order is correct here?
> 

Ideally, BDF (1:0.0) should be assinged the Device ID of 0x5a01. But based on my
experiments, it doesn't work. But if the Device ID gets swapped, it works.

Maybe I should add a comment here.

Thanks,
Mani

> > +			msi-map-mask = <0xff00>;
> >   			interrupt-map-mask = <0 0 0 0x7>;
> >   			interrupt-map = <0 0 0 1 &intc 0 0 0 434 IRQ_TYPE_LEVEL_HIGH>, /* int_a */
> >   					<0 0 0 2 &intc 0 0 0 435 IRQ_TYPE_LEVEL_HIGH>, /* int_b */
> 
> -- 
> With best wishes
> Dmitry
> 

-- 
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