Re: [PATCH net-next] i2c: tegra: runtime PM is not IRQ-safe

["Russell King (Oracle)" <linux@armlinux.org.uk>]

Please ignore the net-next in the subject line, but yes, that was the
tree this patch was generated against.

On Tue, Feb 17, 2026 at 03:40:47PM +0000, Russell King (Oracle) wrote:
> i2c-tegra marks its runtime PM as IRQ safe using pm_runtime_irq_safe().
> However, tegra_i2c_runtime_suspend() calls
> pinctrl_pm_select_idle_state(), which eventually calls
> pinmux_disable_setting() which will take the desc->mux_lock mutex.
> When this happens, the result is:
> 
> BUG: sleeping function called from invalid context at kernel/locking/mutex.c:591
> in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 12, name: kworker/u24:0
> preempt_count: 0, expected: 0
> RCU nest depth: 0, expected: 0
> 3 locks held by kworker/u24:0/12:
>  #0: ffff000080020d48 ((wq_completion)events_unbound#2){+.+.}-{0:0}, at: process_one_work+0x184/0x628
>  #1: ffff80008225bde8 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1ac/0x628
>  #2: ffff000080ad90f8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x2c/0x188
> irq event stamp: 97058
> ktime_get+0x130/0x180
> _raw_spin_lock_irqsave+0x84/0x88
> handle_softirqs+0x448/0x494
> __do_softirq+0x14/0x20
> CPU: 1 UID: 0 PID: 12 Comm: kworker/u24:0 Not tainted 6.19.0-rc8-net-next+ #591 PREEMPT
> Hardware name: NVIDIA NVIDIA Jetson Xavier NX Developer Kit/Jetson, BIOS 6.0-37391689 08/28/2024
> Workqueue: events_unbound deferred_probe_work_func
> Call trace:
>  show_stack+0x18/0x30 (C)
>  dump_stack_lvl+0x6c/0x94
>  dump_stack+0x18/0x24
>  __might_resched+0x154/0x220
>  __might_sleep+0x48/0x80
>  __mutex_lock+0x48/0x800
>  mutex_lock_nested+0x24/0x30
>  pinmux_disable_setting+0x9c/0x180
>  pinctrl_commit_state+0x5c/0x260
>  pinctrl_pm_select_idle_state+0x4c/0xa0
>  tegra_i2c_runtime_suspend+0x2c/0x3c
>  pm_generic_runtime_suspend+0x2c/0x44
>  __rpm_callback+0x48/0x1ec
>  rpm_callback+0x74/0x80
>  rpm_suspend+0xec/0x630
>  rpm_idle+0x274/0x42c
>  __pm_runtime_idle+0x44/0x154
>  tegra_i2c_probe+0x2c0/0x540
>  platform_probe+0x5c/0xa4
>  really_probe+0xbc/0x2c0
>  __driver_probe_device+0x78/0x120
>  driver_probe_device+0x3c/0x160
>  __device_attach_driver+0xb8/0x140
>  bus_for_each_drv+0x70/0xb8
>  __device_attach+0xa4/0x188
>  device_initial_probe+0x50/0x54
>  bus_probe_device+0x38/0xa4
>  deferred_probe_work_func+0x90/0xcc
>  process_one_work+0x204/0x628
>  worker_thread+0x1bc/0x360
>  kthread+0x138/0x210
>  ret_from_fork+0x10/0x20
> 
> This was observed on the nVidia Jetson Xavier NX platform.
> 
> Thus, no, the runtime PM is not IRQ-safe. Remove the call marking it as
> such.
> 
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> ---
> The IRQ-safe marking was introduced by commit ede2299f7101 ("i2c:
> tegra: Support atomic transfers").
> 
> However, since then there have been patches disabling the IRQ-safe
> marking:
> 
> 9e29420ddb13 i2c: tegra: Don't mark VI I2C as IRQ safe runtime PM
> 14d069d92951 i2c: tegra: Do not mark ACPI devices as irq safe
> 
> Clearly, the presence of pinctrl_pm_select_idle_state() which can sleep
> means, definitively, that runtime PM on this device is not IRQ safe,
> and if the original patch introducing atomic transfers relies on these
> being IRQ safe, that patch was incorrect (maybe on such devices, it
> should not change the pin state, and the driver should have a flag to
> allow the driver to be used in atomic contexts?)
> 
> The alternative to this patch is to get rid of the pinctrl calls in the
> runtime PM path.
> ---
>  drivers/i2c/busses/i2c-tegra.c | 12 ------------
>  1 file changed, 12 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> index e533460bccc3..878a2d1c9749 100644
> --- a/drivers/i2c/busses/i2c-tegra.c
> +++ b/drivers/i2c/busses/i2c-tegra.c
> @@ -1829,18 +1829,6 @@ static int tegra_i2c_probe(struct platform_device *pdev)
>  	if (err)
>  		goto release_clocks;
>  
> -	/*
> -	 * VI I2C is in VE power domain which is not always ON and not
> -	 * IRQ-safe.  Thus, IRQ-safe device shouldn't be attached to a
> -	 * non IRQ-safe domain because this prevents powering off the power
> -	 * domain.
> -	 *
> -	 * VI I2C device shouldn't be marked as IRQ-safe because VI I2C won't
> -	 * be used for atomic transfers. ACPI device is not IRQ safe also.
> -	 */
> -	if (!IS_VI(i2c_dev) && !has_acpi_companion(i2c_dev->dev))
> -		pm_runtime_irq_safe(i2c_dev->dev);
> -
>  	pm_runtime_enable(i2c_dev->dev);
>  
>  	err = tegra_i2c_init_hardware(i2c_dev);
> -- 
> 2.47.3
> 
> 

-- 
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