Re: [PATCH v2 10/15] PCI: rcar-gen4: Take over the iMSI-RX interrupt

[Geert Uytterhoeven]

Hi Den-san, Marek,

On Mon, 28 Sept 2026 at 18:53, Koichiro Den <den@xxxxxxxxxxxxx> wrote:
> On R-Car Gen4, intreq_pcim_sub ("msi") carries more than the integrated
> MSI receiver: the controller's reset requests and the Root Port's PME
> and bandwidth notifications are signalled on the same line, and the
> following patches need to handle them. With the DesignWare core owning
> the line through its chained handler, the driver would have to hook into
> that handler when iMSI-RX is used and request the line itself otherwise.
>
> Instead, request the interrupt in the driver in all configurations and
> set pp->msi_irq[0] to -ENODEV so the core does not install its chained
> handler, as spear13xx, keembay and dra7xx do. The handler demultiplexes
> the MSIs through dw_handle_msi_irq() when the APP block reports
> msi_ctrl_int. With an external MSI controller or pci=nomsi the iMSI-RX
> is not set up, so keep msi_ctrl_int masked rather than enabled, and the
> handler has nothing to do there yet. Request the interrupt before
> enumeration, as endpoint drivers may use MSIs from their probe, with
> IRQF_NO_THREAD so the MSIs are demultiplexed in hard IRQ context like
> the chained handler did. The interrupt is required by the binding.
>
> Release the interrupt in .deinit, before asserting the controller reset
> and disabling its clocks. Disable it around a Root Port reset because
> the handler accesses the MSI status registers through DBI.
>
> The DT routes downstream INTx to the same line, but the driver has never
> supported INTx (no INTx domain, INTx enables never set), so requesting
> the line exclusively takes nothing away.
>
> Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>

Thanks for your patch!

FTR, this interacts badly with "[PATCH v2] PCI: rcar-gen4: Add missing
PM ops"[1] during resume from s2idle:

    Unbalanced enable for IRQ 57
    WARNING: kernel/irq/manage.c:775 at __enable_irq+0x38/0x64, CPU#3:
s2idle/686
    Modules linked in:
    CPU: 3 UID: 0 PID: 686 Comm: s2idle Not tainted
7.3.0-rc5-rcar3-09216-ga295839bfe55 #696 PREEMPT
    Hardware name: Renesas Gray Hawk Single board based on r8a779h0 (DT)
    pstate: 604000c5 (nZCv daIF +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
    pc : __enable_irq+0x38/0x64
    lr : __enable_irq+0x38/0x64
    sp : ffffffc08904bab0
    x29: ffffffc08904bab0 x28: ffffff8446a4a880 x27: ffffffc084e64828
    x26: ffffffc084e64838 x25: ffffffc08069e630 x24: ffffff8443ad7cb0
    x23: 0000000000000000 x22: 0000000000000000 x21: 0000000000000070
    x20: 0000000000000039 x19: ffffff8443ad7c00 x18: 00000000e630bb27
    x17: 0000000000000000 x16: 0000000000000000 x15: 0720072007200720
    x14: 0720072007200720 x13: 0720072007200720 x12: 0000000000000566
    x11: 0000000000000000 x10: ffffffc08418a038 x9 : ffffffc08158a090
    x8 : ffffffc08904b798 x7 : ffffffc08904b7a0 x6 : 3ffffffffff7ffff
    x5 : fffffffffff7ffff x4 : 0000000000000000 x3 : 0000000000000000
    x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffff8446a4a880
    Call trace:
     __enable_irq+0x38/0x64 (P)
     resume_irqs+0xf0/0x130
     resume_device_irqs+0x10/0x18
     dpm_resume_noirq+0xe8/0x190
     suspend_devices_and_enter+0x524/0x594
     pm_suspend+0x22c/0x270
     state_store+0xa8/0xe8
     kobj_attr_store+0x14/0x24
     sysfs_kf_write+0x4c/0x64
     kernfs_fop_write_iter+0x13c/0x184
     vfs_write+0x148/0x1b4
     ksys_write+0x78/0xe0
     __arm64_sys_write+0x14/0x1c
     invoke_syscall+0xa0/0x100
     el0_svc_common.constprop.0+0xb0/0xcc
     do_el0_svc+0x18/0x20
     el0_svc+0x3c/0x114
     el0t_64_sync_handler+0x58/0x134
     el0t_64_sync+0x158/0x15c
    irq event stamp: 0
    hardirqs last  enabled at (0): [<0000000000000000>] 0x0
    hardirqs last disabled at (0): [<ffffffc080092a2c>]
copy_process+0x9e0/0x17b8
    softirqs last  enabled at (0): [<ffffffc080092a34>]
copy_process+0x9e8/0x17b8
    softirqs last disabled at (0): [<0000000000000000>] 0x0
    ---[ end trace 0000000000000000 ]---

[1] https://lore.kernel.org/20260907153711.653861-1-marek.vasut+renesas@xxxxxxxxxxx/

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds