Re: [PATCH v3 2/4] drm/xe/sysctrl: Add system controller interrupt handler

["Mallesh, Koujalagi" <mallesh.koujalagi@intel.com>]

On 12-03-2026 02:36 pm, Raag Jadav wrote:
> Add system controller interrupt handler which is denoted by 11th bit in
> GFX master interrupt register. While at it, add worker for scheduling
> system controller work.
>
> Co-developed-by: Soham Purkait <soham.purkait@intel.com>
> Signed-off-by: Soham Purkait <soham.purkait@intel.com>
> Signed-off-by: Raag Jadav <raag.jadav@intel.com>
> ---
> v2: Use system_percpu_wq instead of dedicated (Matthew Brost)
> ---
>   drivers/gpu/drm/xe/regs/xe_irq_regs.h |  1 +
>   drivers/gpu/drm/xe/xe_irq.c           |  2 ++
>   drivers/gpu/drm/xe/xe_sysctrl.c       | 39 ++++++++++++++++++++++-----
>   drivers/gpu/drm/xe/xe_sysctrl.h       |  1 +
>   drivers/gpu/drm/xe/xe_sysctrl_types.h |  7 +++++
>   5 files changed, 43 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/regs/xe_irq_regs.h b/drivers/gpu/drm/xe/regs/xe_irq_regs.h
> index 9d74f454d3ff..1d6b976c4de0 100644
> --- a/drivers/gpu/drm/xe/regs/xe_irq_regs.h
> +++ b/drivers/gpu/drm/xe/regs/xe_irq_regs.h
> @@ -22,6 +22,7 @@
>   #define   DISPLAY_IRQ				REG_BIT(16)
>   #define   SOC_H2DMEMINT_IRQ			REG_BIT(13)
>   #define   I2C_IRQ				REG_BIT(12)
> +#define   SYSCTRL_IRQ				REG_BIT(11)
>   #define   GT_DW_IRQ(x)				REG_BIT(x)
>   
>   /*
> diff --git a/drivers/gpu/drm/xe/xe_irq.c b/drivers/gpu/drm/xe/xe_irq.c
> index 9a775c6588dc..e9f0b3cad06d 100644
> --- a/drivers/gpu/drm/xe/xe_irq.c
> +++ b/drivers/gpu/drm/xe/xe_irq.c
> @@ -24,6 +24,7 @@
>   #include "xe_mmio.h"
>   #include "xe_pxp.h"
>   #include "xe_sriov.h"
> +#include "xe_sysctrl.h"
>   #include "xe_tile.h"
>   
>   /*
> @@ -525,6 +526,7 @@ static irqreturn_t dg1_irq_handler(int irq, void *arg)
>   				xe_heci_csc_irq_handler(xe, master_ctl);
>   			xe_display_irq_handler(xe, master_ctl);
>   			xe_i2c_irq_handler(xe, master_ctl);
> +			xe_sysctrl_irq_handler(xe, master_ctl);
>   			xe_mert_irq_handler(xe, master_ctl);
>   			gu_misc_iir = gu_misc_irq_ack(xe, master_ctl);
>   		}
> diff --git a/drivers/gpu/drm/xe/xe_sysctrl.c b/drivers/gpu/drm/xe/xe_sysctrl.c
> index 365f73ef680d..30349df1c04b 100644
> --- a/drivers/gpu/drm/xe/xe_sysctrl.c
> +++ b/drivers/gpu/drm/xe/xe_sysctrl.c
> @@ -8,6 +8,7 @@
>   
>   #include <drm/drm_managed.h>
>   
> +#include "regs/xe_irq_regs.h"
>   #include "regs/xe_sysctrl_regs.h"
>   #include "xe_assert.h"
>   #include "xe_device.h"
> @@ -33,10 +34,16 @@
>   static void sysctrl_fini(void *arg)
>   {
>   	struct xe_device *xe = arg;
> +	struct xe_sysctrl *sc = &xe->sc;
>   
> +	cancel_work_sync(&sc->work);
>   	xe->soc_remapper.set_sysctrl_region(xe, 0);
>   }
>   
> +static void xe_sysctrl_work(struct work_struct *work)
> +{
> +}
> +
>   /**
>    * xe_sysctrl_init() - Initialize System Controller subsystem
>    * @xe: xe device instance
> @@ -60,12 +67,6 @@ int xe_sysctrl_init(struct xe_device *xe)
>   
>   	xe_assert(xe, xe->soc_remapper.set_sysctrl_region);
>   
> -	xe->soc_remapper.set_sysctrl_region(xe, SYSCTRL_MAILBOX_INDEX);
> -
> -	ret = devm_add_action_or_reset(xe->drm.dev, sysctrl_fini, xe);
> -	if (ret)
> -		return ret;
> -
>   	sc->mmio = devm_kzalloc(xe->drm.dev, sizeof(*sc->mmio), GFP_KERNEL);
>   	if (!sc->mmio)
>   		return -ENOMEM;
> @@ -78,7 +79,31 @@ int xe_sysctrl_init(struct xe_device *xe)
>   	if (ret)
>   		return ret;
>   
> +	ret = drmm_mutex_init(&xe->drm, &sc->work_lock);
> +	if (ret)
> +		return ret;
> +
> +	xe->soc_remapper.set_sysctrl_region(xe, SYSCTRL_MAILBOX_INDEX);
>   	xe_sysctrl_mailbox_init(sc);
> +	INIT_WORK(&sc->work, xe_sysctrl_work);
>   
> -	return 0;
> +	return devm_add_action_or_reset(xe->drm.dev, sysctrl_fini, xe);
> +}
> +
> +/**
> + * xe_sysctrl_irq_handler() - Handler for System Controller interrupts
> + * @xe: xe device instance
> + * @master_ctl: interrupt register
> + *
> + * Handle interrupts generated by System Controller.
> + */
> +void xe_sysctrl_irq_handler(struct xe_device *xe, u32 master_ctl)
> +{
> +	struct xe_sysctrl *sc = &xe->sc;
> +
> +	if (!xe->info.has_sysctrl)
> +		return;
> +

We need to check sc->work.func if NULL then return, since initialization 
of interrupt enabled @ line: 923 xe_irq_install() after that line 989: 
xe_systctrl_init() set the work.func. In between

xe_sysctrl_irq_handler fired then work.func is NULL and going to 
schedule work which lead to panic @ worker->current_func(work).

Thanks,

-/Mallesh

> +	if (master_ctl & SYSCTRL_IRQ)
> +		schedule_work(&sc->work);
>   }
> diff --git a/drivers/gpu/drm/xe/xe_sysctrl.h b/drivers/gpu/drm/xe/xe_sysctrl.h
> index d5d8735038ae..ff60d42b52a7 100644
> --- a/drivers/gpu/drm/xe/xe_sysctrl.h
> +++ b/drivers/gpu/drm/xe/xe_sysctrl.h
> @@ -17,5 +17,6 @@ static inline struct xe_device *sc_to_xe(struct xe_sysctrl *sc)
>   }
>   
>   int xe_sysctrl_init(struct xe_device *xe);
> +void xe_sysctrl_irq_handler(struct xe_device *xe, u32 master_ctl);
>   
>   #endif
> diff --git a/drivers/gpu/drm/xe/xe_sysctrl_types.h b/drivers/gpu/drm/xe/xe_sysctrl_types.h
> index 8217f6befe70..13fbf2990280 100644
> --- a/drivers/gpu/drm/xe/xe_sysctrl_types.h
> +++ b/drivers/gpu/drm/xe/xe_sysctrl_types.h
> @@ -8,6 +8,7 @@
>   
>   #include <linux/mutex.h>
>   #include <linux/types.h>
> +#include <linux/workqueue_types.h>
>   
>   struct xe_mmio;
>   
> @@ -27,6 +28,12 @@ struct xe_sysctrl {
>   
>   	/** @phase_bit: Message boundary phase toggle bit (0 or 1) */
>   	bool phase_bit;
> +
> +	/** @work: Pending events work */
> +	struct work_struct work;
> +
> +	/** @work_lock: Mutex protecting pending events */
> +	struct mutex work_lock;
>   };
>   
>   #endif