Re: [PATCH] arm64: dts: ls208xa: use a pseudo-bus to constrain usb dma size

[Krzysztof Kozlowski]

On 14/09/2023 16:56, Laurentiu Tudor wrote:
> Wrap the usb controllers in an intermediate simple-bus and use it to
> constrain the dma address size of these usb controllers to the 40b
> that they generate toward the interconnect. This is required because
> the SoC uses 48b address sizes and this mismatch would lead to smmu
> context faults [1] because the usb generates 40b addresses while the
> smmu page tables are populated with 48b wide addresses.
> 
> [1]
> xhci-hcd xhci-hcd.0.auto: xHCI Host Controller
> xhci-hcd xhci-hcd.0.auto: new USB bus registered, assigned bus number 1
> xhci-hcd xhci-hcd.0.auto: hcc params 0x0220f66d hci version 0x100 quirks 0x0000000002000010
> xhci-hcd xhci-hcd.0.auto: irq 108, io mem 0x03100000
> xhci-hcd xhci-hcd.0.auto: xHCI Host Controller
> xhci-hcd xhci-hcd.0.auto: new USB bus registered, assigned bus number 2
> xhci-hcd xhci-hcd.0.auto: Host supports USB 3.0 SuperSpeed
> arm-smmu 5000000.iommu: Unhandled context fault: fsr=0x402, iova=0xffffffb000, fsynr=0x0, cbfrsynra=0xc01, cb=3
> 
> Signed-off-by: Laurentiu Tudor <laurentiu.tudor@xxxxxxx>
> ---
>  .../arm64/boot/dts/freescale/fsl-ls208xa.dtsi | 46 +++++++++++--------
>  1 file changed, 27 insertions(+), 19 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi b/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> index d2f5345d0560..47cc7699ca16 100644
> --- a/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> +++ b/arch/arm64/boot/dts/freescale/fsl-ls208xa.dtsi
> @@ -1186,26 +1186,34 @@
>  			dma-coherent;
>  		};
>  
> -		usb0: usb@3100000 {
> -			status = "disabled";
> -			compatible = "snps,dwc3";
> -			reg = <0x0 0x3100000 0x0 0x10000>;
> -			interrupts = <0 80 0x4>; /* Level high type */
> -			dr_mode = "host";
> -			snps,quirk-frame-length-adjustment = <0x20>;
> -			snps,dis_rxdet_inp3_quirk;
> -			snps,incr-burst-type-adjustment = <1>, <4>, <8>, <16>;
> -		};
> +		aux_bus: aux_bus {

No underscores in node names. The node name should be anyway generic, so
 just "bus".



Best regards,
Krzysztof