Re: [PATCH v4 14/18] PCI: rcar-gen4: Route Root Port AER to a virtual Root Port IRQ

[Marek Vasut <marek.vasut@mailbox.org>]

On 10/15/26 5:30 AM, Koichiro Den wrote:
> On R-Car Gen4 SoCs, the APP block exposes the Root Port interrupt
> signals in PCIEINTSTS0 and routes them to platform IRQs: AER to
> intreq_pcim_lperr, and PME and bandwidth notifications to
> intreq_pcim_sub. On an R-Car S4 with GIC ITS, a link retrain set
> LnkSta.LBMS and latched PCIEINTSTS0[23] (cfg_bw_mgt_msi), but the Root
> Port's MSI never fired while endpoint MSIs worked fine. With iMSI-RX the
> Root Port MSI capabilities are already hidden, but its INTx maps to
> intreq_pcim_sub. Note that even before this driver took over the IRQ
> with rcar_gen4_pcie_msi_irq_handler, the port service was unable to
> request it, as the DWC core used that IRQ for its chained MSI handler.
> In either case, iMSI-RX or an external MSI controller, Root Port
> interrupts are not delivered to the port services.
> 
> Set no_rp_msi so the Root Port services use INTx regardless of the MSI
> controller. Use a virtual IRQ to deliver notifications from separate
> platform IRQs to the standard handlers. Route AER from the optional
> "aer" interrupt. DTs without it remain supported, but Root Port AER
> stays unavailable.
> 
> The APP block may still receive MSI-form notifications because hiding
> the Root Port's MSI capabilities does not clear MSICAP0.MSIE. Handle
> these alongside the INTx-form level signals. Clear the MSI-form latch
> before the AER handler clears Root Error Status, so a late APP clear
> does not erase a new notification.
> 
> Check for reset requests before dispatch: on S4, DBI accesses from
> the port services can hang the host immediately after link down.
> 
> The next patch also feeds PME and bandwidth notifications from "msi"
> into this IRQ, so both parents may dispatch concurrently.
> handle_level_irq() calls irq_ack() before checking whether it can run
> the handlers. Keep the APP latches set while the IRQ is in progress or
> disabled, so the level parents can retry through the reset checks.
> This avoids losing notifications without a raw lock around port
> services that take regular spinlocks.
> 
> Signed-off-by: Koichiro Den <den@valinux.co.jp>

Reviewed-by: Marek Vasut <marek.vasut+renesas@mailbox.org>