mei: vsc: Fix "BUG: Invalid wait context" lockdep error

JIRA: https://issues.redhat.com/browse/RHEL-113185

commit cee3dba
Author: Hans de Goede <hansg@kernel.org>
Date:   Mon Jun 23 10:50:51 2025 +0200

    mei: vsc: Fix "BUG: Invalid wait context" lockdep error

    Kernels build with CONFIG_PROVE_RAW_LOCK_NESTING report the following
    tp-vsc lockdep error:

    =============================
     [ BUG: Invalid wait context ]
     ...
     swapper/10/0 is trying to lock:
     ffff88819c271888 (&tp->xfer_wait){....}-{3:3},
      at: __wake_up (kernel/sched/wait.c:106 kernel/sched/wait.c:127)
     ...
     Call Trace:
     <IRQ>
     ...
     __raw_spin_lock_irqsave (./include/linux/spinlock_api_smp.h:111)
     __wake_up (kernel/sched/wait.c:106 kernel/sched/wait.c:127)
     vsc_tp_isr (drivers/misc/mei/vsc-tp.c:110) mei_vsc_hw
     __handle_irq_event_percpu (kernel/irq/handle.c:158)
     handle_irq_event (kernel/irq/handle.c:195 kernel/irq/handle.c:210)
     handle_edge_irq (kernel/irq/chip.c:833)
     ...
     </IRQ>

    The root-cause of this is the IRQF_NO_THREAD flag used by the intel-pinctrl
    code. Setting IRQF_NO_THREAD requires all interrupt handlers for GPIO ISRs
    to use raw-spinlocks only since normal spinlocks can sleep in PREEMPT-RT
    kernels and with IRQF_NO_THREAD the interrupt handlers will always run in
    an atomic context [1].

    vsc_tp_isr() calls wake_up(&tp->xfer_wait), which uses a regular spinlock,
    breaking the raw-spinlocks only rule for Intel GPIO ISRs.

    Make vsc_tp_isr() run as threaded ISR instead of as hard ISR to fix this.

    Fixes: 566f5ca ("mei: Add transport driver for IVSC device")
    Link: https://lore.kernel.org/linux-gpio/18ab52bd-9171-4667-a600-0f52ab7017ac@kernel.org/ [1]
    Signed-off-by: Hans de Goede <hansg@kernel.org>
    Link: https://lore.kernel.org/r/20250623085052.12347-10-hansg@kernel.org
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Signed-off-by: Steve Best <sbest@redhat.com>

Author: sfbest

drivers/misc/mei/vsc-tp.c

@@ -497,7 +497,7 @@ static int vsc_tp_probe(struct spi_device *spi)
 	tp->spi = spi;
 
 	irq_set_status_flags(spi->irq, IRQ_DISABLE_UNLAZY);
-	ret = request_threaded_irq(spi->irq, vsc_tp_isr, NULL,
+	ret = request_threaded_irq(spi->irq, NULL, vsc_tp_isr,
 				   IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
 				   dev_name(dev), tp);
 	if (ret)