Re: [PATCH v3 13/18] PCI: dwc: Let glue drivers hide the Root Port MSI capabilities

[sashiko-bot@kernel.org]

> Commit f5cd8a929c82 ("PCI: dwc: Remove MSI/MSIX capability for Root Port
> if iMSI-RX is used as MSI controller") hides the Root Port MSI/MSI-X
> capabilities when iMSI-RX is the MSI controller, as it cannot receive
> the Root Port's own MSIs.
> 
> Some platforms cannot deliver them with an external MSI controller
> either. The DesignWare core signals Root Port interrupts (AER, PME,
> bandwidth, hotplug) as sideband signals on its SII interface and only
> turns them into MSI writes with the optional SII2MSI feature. Otherwise
> it is up to the vendor wrapper. The controller on R-Car Gen4 SoCs
> (DWC 5.20a) appears to lack SII2MSI, and its APP block merely latches
> the signals into status registers wired to platform IRQs, so an MSI
> targeted at the GIC ITS is never sent.
> 
> Add a no_rp_msi flag so glue drivers can request the same INTx fallback
> regardless of the MSI controller in use. It is the counterpart of
> 'keep_rp_msi_en' from commit 3a4e8302e72f ("PCI: imx6: Keep Root Port
> MSI capability with iMSI-RX to work around hardware bug"), which keeps
> precedence: that one is needed for endpoint MSIs to work at all, whereas
> hiding the capability only moves the Root Port services to INTx. The
> removal stays in dw_pcie_setup_rc(), which also runs after a Root Port
> reset.
> 
> Signed-off-by: Koichiro Den <den@valinux.co.jp>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20261006084638.3821710-1-den@valinux.co.jp?part=13