Re: [PATCH 5/5] arm64: dts: qcom: qcs8550: add QCS8550 RB5Gen2 board support

Manivannan Sadhasivam
2026-04-09T11:26:14Z

On Thu, Apr 09, 2026 at 11:04:55AM +0100, Joe Sandom wrote:
> On Tue, Apr 07, 2026 at 09:44:34PM +0530, Manivannan Sadhasivam wrote:
> > On Tue, Apr 07, 2026 at 12:39:25PM +0100, Joe Sandom wrote:
> >
> > [...]
> >
> > > > > +&pcie0 {
> > > > > + wake-gpios = <&tlmm 96 GPIO_ACTIVE_HIGH>;
> > > > > + perst-gpios = <&tlmm 94 GPIO_ACTIVE_LOW>;
> > > > > +
> > > > > + pinctrl-0 = <&pcie0_default_state>;
> > > > > + pinctrl-names = "default";
> > > > > +
> > > > > + iommu-map = <0x0 &apps_smmu 0x1400 0x1>,
> > > > > + <0x100 &apps_smmu 0x1401 0x1>,
> > > > > + <0x208 &apps_smmu 0x1402 0x1>,
> > > > > + <0x210 &apps_smmu 0x1403 0x1>,
> > > > > + <0x218 &apps_smmu 0x1404 0x1>,
> > > > > + <0x300 &apps_smmu 0x1407 0x1>,
> > > > > + <0x400 &apps_smmu 0x1408 0x1>,
> > > > > + <0x500 &apps_smmu 0x140c 0x1>,
> > > > > + <0x501 &apps_smmu 0x140e 0x1>;
> > > > > +
> > > > > + /delete-property/ msi-map;
> > > >
> > > > Why?
> > > I tried extending the msi-map to cover the RIDs from the QPS615
> > > PCIe switch (matching the iommu-map entries), but this caused
> > > ITS MAPD command timeouts.
> >
> > I'm not aware of any specific issue with ITS on this chipset. At what time did
> > you see the timeout? During probe?
> So when I set msi-map to match the iommu-map entries, I got this;
> [ 0.000000] ITS [mem 0x17140000-0x1717ffff]
> [ 11.085152] ath12k_wifi7_pci 0001:04:00.0: BAR 0 assigned
> [ 11.115762] ath12k_wifi7_pci 0001:04:00.0: Wi-Fi 7 Hardware name: wcn7850 hw2.0
> [ 11.153632] ath12k_wifi7_pci 0001:04:00.0: MSI vectors: 16
> [ 11.252398] mhi mhi0: Requested to power ON
> .........
> [ 101.596274] mhi mhi0: Wait for device to enter SBL or Mission mode
> [ 101.603098] ath12k_wifi7_pci 0001:04:00.0: failed to set mhi state: POWER_ON(2)
> [ 101.610632] ath12k_wifi7_pci 0001:04:00.0: failed to start mhi: -110
> [ 101.617171] ath12k_wifi7_pci 0001:04:00.0: failed to power up :-110
> [ 101.794431] ath12k_wifi7_pci 0001:04:00.0: probe failed with error -110
> [ 103.158872] ITS queue timeout (12640 12609)
> [ 103.163183] ITS cmd its_build_mapd_cmd failed
>
> With msi-map removed, I got this;
> [ 11.469642] ath12k_wifi7_pci 0001:04:00.0: BAR 0 assigned
> [ 11.490059] ath12k_wifi7_pci 0001:04:00.0: Wi-Fi 7 Hardware name: wcn7850 hw2.0
> [ 11.497787] ath12k_wifi7_pci 0001:04:00.0: MSI vectors: 16
> [ 11.559958] mhi mhi0: Requested to power ON
> [ 11.567375] mhi mhi0: Power on setup success
> [ 11.693069] mhi mhi0: Wait for device to enter SBL or Mission mode
> [ 12.185946] ath12k_wifi7_pci 0001:04:00.0: chip_id 0x2 ... soc_id 0x40170200
> [ 12.482168] ath12k_wifi7_pci 0001:04:00.0 wlP1p4s0: renamed from wlan0

Thanks for the logs. I also checked internally and learned that the timeout is
due to Gunyah limiting the devices per-port. On SM8550, it currently only
allows 2 devices per RC instance to save the memory footprint. So when you
connect a PCIe switch which exposes more than two devices (1 USP + (1+) DSPs),
you'll run out of ITS mapping in Gunyah, leading to these timeouts.

So either you need to modify Gunyah to allow more devices per-port or switch to
iMSI-RX which you are already doing.

- Mani

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