linux-kernel - Re: [PATCH v1] serial: qcom-geni: Fix pinctrl deadlock on runtime resume

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Message-Id: <DCNLSFVPCKMV.K1UE3J3K6JQD@linaro.org>
Date: Mon, 08 Sep 2025 18:43:22 +0100
From: "Alexey Klimov" <alexey.klimov@...aro.org>
To: "Praveen Talari" <praveen.talari@....qualcomm.com>, "Greg Kroah-Hartman"
 <gregkh@...uxfoundation.org>, "Jiri Slaby" <jirislaby@...nel.org>, "Bryan
 O'Donoghue" <bryan.odonoghue@...aro.org>, "Praveen Talari"
 <quic_ptalari@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <linux-serial@...r.kernel.org>
Cc: <psodagud@...cinc.com>, <djaggi@...cinc.com>,
 <quic_msavaliy@...cinc.com>, <quic_vtanuku@...cinc.com>,
 <quic_arandive@...cinc.com>, <quic_mnaresh@...cinc.com>,
 <quic_shazhuss@...cinc.com>
Subject: Re: [PATCH v1] serial: qcom-geni: Fix pinctrl deadlock on runtime
 resume

On Mon Sep 8, 2025 at 5:45 PM BST, Praveen Talari wrote:
> A deadlock is observed in the qcom_geni_serial driver during runtime
> resume. This occurs when the pinctrl subsystem reconfigures device pins
> via msm_pinmux_set_mux() while the serial device's interrupt is an
> active wakeup source. msm_pinmux_set_mux() calls disable_irq() or
> __synchronize_irq(), conflicting with the active wakeup state and
> causing the IRQ thread to enter an uninterruptible (D-state) sleep,
> leading to system instability.
>
> The critical call trace leading to the deadlock is:
>
>     Call trace:
>     __switch_to+0xe0/0x120
>     __schedule+0x39c/0x978
>     schedule+0x5c/0xf8
>     __synchronize_irq+0x88/0xb4
>     disable_irq+0x3c/0x4c
>     msm_pinmux_set_mux+0x508/0x644
>     pinmux_enable_setting+0x190/0x2dc
>     pinctrl_commit_state+0x13c/0x208
>     pinctrl_pm_select_default_state+0x4c/0xa4
>     geni_se_resources_on+0xe8/0x154
>     qcom_geni_serial_runtime_resume+0x4c/0x88
>     pm_generic_runtime_resume+0x2c/0x44
>     __genpd_runtime_resume+0x30/0x80
>     genpd_runtime_resume+0x114/0x29c
>     __rpm_callback+0x48/0x1d8
>     rpm_callback+0x6c/0x78
>     rpm_resume+0x530/0x750
>     __pm_runtime_resume+0x50/0x94
>     handle_threaded_wake_irq+0x30/0x94
>     irq_thread_fn+0x2c/xa8
>     irq_thread+0x160/x248
>     kthread+0x110/x114
>     ret_from_fork+0x10/x20
>
> To resolve this, explicitly manage the wakeup IRQ state within the
> runtime suspend/resume callbacks. In the runtime resume callback, call
> disable_irq_wake() before enabling resources. This preemptively
> removes the "wakeup" capability from the IRQ, allowing subsequent
> interrupt management calls to proceed without conflict. An error path
> re-enables the wakeup IRQ if resource enablement fails.
>
> Conversely, in runtime suspend, call enable_irq_wake() after resources
> are disabled. This ensures the interrupt is configured as a wakeup
> source only once the device has fully entered its low-power state. An
> error path handles disabling the wakeup IRQ if the suspend operation
> fails.
>
> Fixes: 1afa70632c39 ("serial: qcom-geni: Enable PM runtime for serial driver")
> Signed-off-by: Praveen Talari <praveen.talari@....qualcomm.com>

You forgot:

Reported-by: Alexey Klimov <alexey.klimov@...aro.org>

Also, not sure where this change will go, via Greg or Jiri, but ideally
this should be picked for current -rc cycle since regression is
introduced during latest merge window.

I also would like to test it on qrb2210 rb1 where this regression is
reproduciable.

Thanks,
Alexey

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