On Mon, 12 Jan 2026 15:37:50 +0100 Nicolas Frattaroli <[email protected]> wrote:
> The current IRQ helpers do not guarantee mutual exclusion that covers > the entire transaction from accessing the mask member and modifying the > mask register. > > This makes it hard, if not impossible, to implement mask modification > helpers that may change one of these outside the normal > suspend/resume/isr code paths. > > Add a spinlock to struct panthor_irq that protects both the mask member > and register. Acquire it in all code paths that access these, but drop > it before processing the threaded handler function. Then, add the > aforementioned new helpers: enable_events, and disable_events. They work > by ORing and NANDing the mask bits. > > resume is changed to no longer have a mask passed, as pirq->mask is > supposed to be the user-requested mask now, rather than a mirror of the > INT_MASK register contents. Users of the resume helper are adjusted > accordingly, including a rather painful refactor in panthor_mmu.c. > > Signed-off-by: Nicolas Frattaroli <[email protected]> > --- > drivers/gpu/drm/panthor/panthor_device.h | 72 +++++++-- > drivers/gpu/drm/panthor/panthor_fw.c | 3 +- > drivers/gpu/drm/panthor/panthor_gpu.c | 2 +- > drivers/gpu/drm/panthor/panthor_mmu.c | 247 > ++++++++++++++++--------------- > drivers/gpu/drm/panthor/panthor_pwr.c | 2 +- > 5 files changed, 187 insertions(+), 139 deletions(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_device.h > b/drivers/gpu/drm/panthor/panthor_device.h > index 424f6cd1a814..0a29234ac58c 100644 > --- a/drivers/gpu/drm/panthor/panthor_device.h > +++ b/drivers/gpu/drm/panthor/panthor_device.h > @@ -84,11 +84,14 @@ struct panthor_irq { > /** @irq: IRQ number. */ > int irq; > > - /** @mask: Current mask being applied to xxx_INT_MASK. */ > + /** @mask: Values to write to xxx_INT_MASK if active. */ > u32 mask; > > /** @state: one of &enum panthor_irq_state reflecting the current > state. */ > atomic_t state; > + > + /** @mask_lock: protects modifications to _INT_MASK and @mask */ > + spinlock_t mask_lock; > }; > > /** > @@ -422,6 +425,8 @@ static irqreturn_t panthor_ ## __name ## > _irq_raw_handler(int irq, void *data) > struct panthor_device *ptdev = pirq->ptdev; > \ > enum panthor_irq_state state; > \ > > \ > + guard(spinlock_irqsave)(&pirq->mask_lock); > \ > + > \ > state = atomic_read(&pirq->state); > \ > if (state == PANTHOR_IRQ_STATE_SUSPENDED || state == > PANTHOR_IRQ_STATE_SUSPENDING) \ > return IRQ_NONE; > \ > @@ -438,11 +443,16 @@ static irqreturn_t panthor_ ## __name ## > _irq_threaded_handler(int irq, void *da > struct panthor_device *ptdev = pirq->ptdev; > \ > enum panthor_irq_state state; > \ > irqreturn_t ret = IRQ_NONE; > \ > + u32 mask; > \ > > \ > - atomic_cmpxchg(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE, > PANTHOR_IRQ_STATE_PROCESSING); \ > + scoped_guard(spinlock_irqsave, &pirq->mask_lock) { > \ > + mask = pirq->mask; > \ > + atomic_cmpxchg(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE, > \ > + PANTHOR_IRQ_STATE_PROCESSING); > \ > + } > \ > > \ > while (true) { > \ > - u32 status = gpu_read(ptdev, __reg_prefix ## _INT_RAWSTAT) & > pirq->mask; \ > + u32 status = (gpu_read(ptdev, __reg_prefix ## _INT_RAWSTAT) & > mask); \ > > \ > if (!status) > \ > break; > \ > @@ -451,12 +461,16 @@ static irqreturn_t panthor_ ## __name ## > _irq_threaded_handler(int irq, void *da > ret = IRQ_HANDLED; > \ > } > \ > > \ > - state = atomic_read(&pirq->state); > \ > - if (state != PANTHOR_IRQ_STATE_SUSPENDED && state != > PANTHOR_IRQ_STATE_SUSPENDING) { \ > - /* Only restore the bits that were used and are still enabled > */ \ > - gpu_write(ptdev, __reg_prefix ## _INT_MASK, > \ > - gpu_read(ptdev, __reg_prefix ## _INT_MASK) | (mask & > pirq->mask)); \ > - atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE); > \ > + scoped_guard(spinlock_irqsave, &pirq->mask_lock) { > \ > + state = atomic_read(&pirq->state); > \ > + if (state != PANTHOR_IRQ_STATE_SUSPENDED && > \ > + state != PANTHOR_IRQ_STATE_SUSPENDING) { > \ > + /* Only restore the bits that were used and are still > enabled */ \ > + gpu_write(ptdev, __reg_prefix ## _INT_MASK, > \ > + gpu_read(ptdev, __reg_prefix ## _INT_MASK) | > \ > + (mask & pirq->mask)); > \ > + atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE); > \ > + } > \ > } > \ > > \ > return ret; > \ > @@ -464,16 +478,18 @@ static irqreturn_t panthor_ ## __name ## > _irq_threaded_handler(int irq, void *da > > \ > static inline void panthor_ ## __name ## _irq_suspend(struct panthor_irq > *pirq) \ > { > \ > - pirq->mask = 0; > \ > - gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, 0); > \ > - atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDING); > \ > + scoped_guard(spinlock_irqsave, &pirq->mask_lock) { > \ > + gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, 0); > \ > + atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDING); > \ > + } > \ > synchronize_irq(pirq->irq); > \ > atomic_set(&pirq->state, PANTHOR_IRQ_STATE_SUSPENDED); > \ > } > \ > > \ > -static inline void panthor_ ## __name ## _irq_resume(struct panthor_irq > *pirq, u32 mask) \ > +static inline void panthor_ ## __name ## _irq_resume(struct panthor_irq > *pirq) \ > { > \ > - pirq->mask = mask; > \ > + guard(spinlock_irqsave)(&pirq->mask_lock); > \ > + > \ > atomic_set(&pirq->state, PANTHOR_IRQ_STATE_ACTIVE); > \ > gpu_write(pirq->ptdev, __reg_prefix ## _INT_CLEAR, pirq->mask); > \ > gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, pirq->mask); > \ > @@ -485,13 +501,39 @@ static int panthor_request_ ## __name ## _irq(struct > panthor_device *ptdev, \ > { > \ > pirq->ptdev = ptdev; > \ > pirq->irq = irq; > \ > - panthor_ ## __name ## _irq_resume(pirq, mask); > \ > + pirq->mask = mask; > \ > + spin_lock_init(&pirq->mask_lock); > \ > + panthor_ ## __name ## _irq_resume(pirq); > \ > > \ > return devm_request_threaded_irq(ptdev->base.dev, irq, > \ > panthor_ ## __name ## > _irq_raw_handler, \ > panthor_ ## __name ## > _irq_threaded_handler, \ > IRQF_SHARED, KBUILD_MODNAME "-" # > __name, \ > pirq); > \ > +} > \ > + > \ > +static inline void panthor_ ## __name ## _irq_enable_events(struct > panthor_irq *pirq, u32 mask) \ > +{ > \ > + enum panthor_irq_state state; > \ > + > \ > + guard(spinlock_irqsave)(&pirq->mask_lock); > \ > + > \ > + state = atomic_read(&pirq->state); > \ > + pirq->mask |= mask; > \ > + if (state != PANTHOR_IRQ_STATE_SUSPENDED || state != > PANTHOR_IRQ_STATE_SUSPENDING) \ > + gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, pirq->mask); > \ > +} > \ > + > \ > +static inline void panthor_ ## __name ## _irq_disable_events(struct > panthor_irq *pirq, u32 mask)\ > +{ > \ > + enum panthor_irq_state state; > \ > + > \ > + guard(spinlock_irqsave)(&pirq->mask_lock); > \ > + > \ > + state = atomic_read(&pirq->state); > \ > + pirq->mask &= ~mask; > \ > + if (state != PANTHOR_IRQ_STATE_SUSPENDED || state != > PANTHOR_IRQ_STATE_SUSPENDING) \ > + gpu_write(pirq->ptdev, __reg_prefix ## _INT_MASK, pirq->mask); > \ > } > > extern struct workqueue_struct *panthor_cleanup_wq; > diff --git a/drivers/gpu/drm/panthor/panthor_fw.c > b/drivers/gpu/drm/panthor/panthor_fw.c > index a64ec8756bed..0e46625f7621 100644 > --- a/drivers/gpu/drm/panthor/panthor_fw.c > +++ b/drivers/gpu/drm/panthor/panthor_fw.c > @@ -1080,7 +1080,8 @@ static int panthor_fw_start(struct panthor_device > *ptdev) > bool timedout = false; > > ptdev->fw->booted = false; > - panthor_job_irq_resume(&ptdev->fw->irq, ~0); > + panthor_job_irq_enable_events(&ptdev->fw->irq, ~0); > + panthor_job_irq_resume(&ptdev->fw->irq); > gpu_write(ptdev, MCU_CONTROL, MCU_CONTROL_AUTO); > > if (!wait_event_timeout(ptdev->fw->req_waitqueue, > diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c > b/drivers/gpu/drm/panthor/panthor_gpu.c > index 057e167468d0..9304469a711a 100644 > --- a/drivers/gpu/drm/panthor/panthor_gpu.c > +++ b/drivers/gpu/drm/panthor/panthor_gpu.c > @@ -395,7 +395,7 @@ void panthor_gpu_suspend(struct panthor_device *ptdev) > */ > void panthor_gpu_resume(struct panthor_device *ptdev) > { > - panthor_gpu_irq_resume(&ptdev->gpu->irq, GPU_INTERRUPTS_MASK); > + panthor_gpu_irq_resume(&ptdev->gpu->irq); > panthor_hw_l2_power_on(ptdev); > } > > diff --git a/drivers/gpu/drm/panthor/panthor_mmu.c > b/drivers/gpu/drm/panthor/panthor_mmu.c > index 198d59f42578..71b8318eab31 100644 > --- a/drivers/gpu/drm/panthor/panthor_mmu.c > +++ b/drivers/gpu/drm/panthor/panthor_mmu.c > @@ -655,125 +655,6 @@ static void panthor_vm_release_as_locked(struct > panthor_vm *vm) > vm->as.id = -1; > } > > -/** > - * panthor_vm_active() - Flag a VM as active > - * @vm: VM to flag as active. > - * > - * Assigns an address space to a VM so it can be used by the GPU/MCU. > - * > - * Return: 0 on success, a negative error code otherwise. > - */ > -int panthor_vm_active(struct panthor_vm *vm) > -{ > - struct panthor_device *ptdev = vm->ptdev; > - u32 va_bits = GPU_MMU_FEATURES_VA_BITS(ptdev->gpu_info.mmu_features); > - struct io_pgtable_cfg *cfg = > &io_pgtable_ops_to_pgtable(vm->pgtbl_ops)->cfg; > - int ret = 0, as, cookie; > - u64 transtab, transcfg; > - > - if (!drm_dev_enter(&ptdev->base, &cookie)) > - return -ENODEV; > - > - if (refcount_inc_not_zero(&vm->as.active_cnt)) > - goto out_dev_exit; > - > - /* Make sure we don't race with lock/unlock_region() calls > - * happening around VM bind operations. > - */ > - mutex_lock(&vm->op_lock); > - mutex_lock(&ptdev->mmu->as.slots_lock); > - > - if (refcount_inc_not_zero(&vm->as.active_cnt)) > - goto out_unlock; > - > - as = vm->as.id; > - if (as >= 0) { > - /* Unhandled pagefault on this AS, the MMU was disabled. We > need to > - * re-enable the MMU after clearing+unmasking the AS interrupts. > - */ > - if (ptdev->mmu->as.faulty_mask & > panthor_mmu_as_fault_mask(ptdev, as)) > - goto out_enable_as; > - > - goto out_make_active; > - } > - > - /* Check for a free AS */ > - if (vm->for_mcu) { > - drm_WARN_ON(&ptdev->base, ptdev->mmu->as.alloc_mask & BIT(0)); > - as = 0; > - } else { > - as = ffz(ptdev->mmu->as.alloc_mask | BIT(0)); > - } > - > - if (!(BIT(as) & ptdev->gpu_info.as_present)) { > - struct panthor_vm *lru_vm; > - > - lru_vm = list_first_entry_or_null(&ptdev->mmu->as.lru_list, > - struct panthor_vm, > - as.lru_node); > - if (drm_WARN_ON(&ptdev->base, !lru_vm)) { > - ret = -EBUSY; > - goto out_unlock; > - } > - > - drm_WARN_ON(&ptdev->base, > refcount_read(&lru_vm->as.active_cnt)); > - as = lru_vm->as.id; > - > - ret = panthor_mmu_as_disable(ptdev, as, true); > - if (ret) > - goto out_unlock; > - > - panthor_vm_release_as_locked(lru_vm); > - } > - > - /* Assign the free or reclaimed AS to the FD */ > - vm->as.id = as; > - set_bit(as, &ptdev->mmu->as.alloc_mask); > - ptdev->mmu->as.slots[as].vm = vm; > - > -out_enable_as: > - transtab = cfg->arm_lpae_s1_cfg.ttbr; > - transcfg = AS_TRANSCFG_PTW_MEMATTR_WB | > - AS_TRANSCFG_PTW_RA | > - AS_TRANSCFG_ADRMODE_AARCH64_4K | > - AS_TRANSCFG_INA_BITS(55 - va_bits); > - if (ptdev->coherent) > - transcfg |= AS_TRANSCFG_PTW_SH_OS; > - > - /* If the VM is re-activated, we clear the fault. */ > - vm->unhandled_fault = false; > - > - /* Unhandled pagefault on this AS, clear the fault and re-enable > interrupts > - * before enabling the AS. > - */ > - if (ptdev->mmu->as.faulty_mask & panthor_mmu_as_fault_mask(ptdev, as)) { > - gpu_write(ptdev, MMU_INT_CLEAR, > panthor_mmu_as_fault_mask(ptdev, as)); > - ptdev->mmu->as.faulty_mask &= ~panthor_mmu_as_fault_mask(ptdev, > as); > - ptdev->mmu->irq.mask |= panthor_mmu_as_fault_mask(ptdev, as); > - gpu_write(ptdev, MMU_INT_MASK, ~ptdev->mmu->as.faulty_mask); > - } > - > - /* The VM update is guarded by ::op_lock, which we take at the beginning > - * of this function, so we don't expect any locked region here. > - */ > - drm_WARN_ON(&vm->ptdev->base, vm->locked_region.size > 0); > - ret = panthor_mmu_as_enable(vm->ptdev, vm->as.id, transtab, transcfg, > vm->memattr); > - > -out_make_active: > - if (!ret) { > - refcount_set(&vm->as.active_cnt, 1); > - list_del_init(&vm->as.lru_node); > - } > - > -out_unlock: > - mutex_unlock(&ptdev->mmu->as.slots_lock); > - mutex_unlock(&vm->op_lock); > - > -out_dev_exit: > - drm_dev_exit(cookie); > - return ret; > -} > - > /** > * panthor_vm_idle() - Flag a VM idle > * @vm: VM to flag as idle. > @@ -1762,6 +1643,128 @@ static void panthor_mmu_irq_handler(struct > panthor_device *ptdev, u32 status) > } > PANTHOR_IRQ_HANDLER(mmu, MMU, panthor_mmu_irq_handler); > > +/** > + * panthor_vm_active() - Flag a VM as active > + * @vm: VM to flag as active. > + * > + * Assigns an address space to a VM so it can be used by the GPU/MCU. > + * > + * Return: 0 on success, a negative error code otherwise. > + */ > +int panthor_vm_active(struct panthor_vm *vm) > +{ > + struct panthor_device *ptdev = vm->ptdev; > + u32 va_bits = GPU_MMU_FEATURES_VA_BITS(ptdev->gpu_info.mmu_features); > + struct io_pgtable_cfg *cfg = > &io_pgtable_ops_to_pgtable(vm->pgtbl_ops)->cfg; > + int ret = 0, as, cookie; > + u64 transtab, transcfg; > + u32 fault_mask; > + > + if (!drm_dev_enter(&ptdev->base, &cookie)) > + return -ENODEV; > + > + if (refcount_inc_not_zero(&vm->as.active_cnt)) > + goto out_dev_exit; > + > + /* Make sure we don't race with lock/unlock_region() calls > + * happening around VM bind operations. > + */ > + mutex_lock(&vm->op_lock); > + mutex_lock(&ptdev->mmu->as.slots_lock); > + > + if (refcount_inc_not_zero(&vm->as.active_cnt)) > + goto out_unlock; > + > + as = vm->as.id; > + if (as >= 0) { > + /* Unhandled pagefault on this AS, the MMU was disabled. We > need to > + * re-enable the MMU after clearing+unmasking the AS interrupts. > + */ > + if (ptdev->mmu->as.faulty_mask & > panthor_mmu_as_fault_mask(ptdev, as)) > + goto out_enable_as; > + > + goto out_make_active; > + } > + > + /* Check for a free AS */ > + if (vm->for_mcu) { > + drm_WARN_ON(&ptdev->base, ptdev->mmu->as.alloc_mask & BIT(0)); > + as = 0; > + } else { > + as = ffz(ptdev->mmu->as.alloc_mask | BIT(0)); > + } > + > + if (!(BIT(as) & ptdev->gpu_info.as_present)) { > + struct panthor_vm *lru_vm; > + > + lru_vm = list_first_entry_or_null(&ptdev->mmu->as.lru_list, > + struct panthor_vm, > + as.lru_node); > + if (drm_WARN_ON(&ptdev->base, !lru_vm)) { > + ret = -EBUSY; > + goto out_unlock; > + } > + > + drm_WARN_ON(&ptdev->base, > refcount_read(&lru_vm->as.active_cnt)); > + as = lru_vm->as.id; > + > + ret = panthor_mmu_as_disable(ptdev, as, true); > + if (ret) > + goto out_unlock; > + > + panthor_vm_release_as_locked(lru_vm); > + } > + > + /* Assign the free or reclaimed AS to the FD */ > + vm->as.id = as; > + set_bit(as, &ptdev->mmu->as.alloc_mask); > + ptdev->mmu->as.slots[as].vm = vm; > + > +out_enable_as: > + transtab = cfg->arm_lpae_s1_cfg.ttbr; > + transcfg = AS_TRANSCFG_PTW_MEMATTR_WB | > + AS_TRANSCFG_PTW_RA | > + AS_TRANSCFG_ADRMODE_AARCH64_4K | > + AS_TRANSCFG_INA_BITS(55 - va_bits); > + if (ptdev->coherent) > + transcfg |= AS_TRANSCFG_PTW_SH_OS; > + > + /* If the VM is re-activated, we clear the fault. */ > + vm->unhandled_fault = false; > + > + /* Unhandled pagefault on this AS, clear the fault and re-enable > interrupts > + * before enabling the AS. > + */ > + fault_mask = panthor_mmu_as_fault_mask(ptdev, as); > + if (ptdev->mmu->as.faulty_mask & fault_mask) { > + gpu_write(ptdev, MMU_INT_CLEAR, fault_mask); > + ptdev->mmu->as.faulty_mask &= ~fault_mask; > + panthor_mmu_irq_enable_events(&ptdev->mmu->irq, fault_mask); > + panthor_mmu_irq_disable_events(&ptdev->mmu->irq, > ptdev->mmu->as.faulty_mask); Why do we need a _disable_events() here? > + } > + > + /* The VM update is guarded by ::op_lock, which we take at the beginning > + * of this function, so we don't expect any locked region here. > + */ > + drm_WARN_ON(&vm->ptdev->base, vm->locked_region.size > 0); > + ret = panthor_mmu_as_enable(vm->ptdev, vm->as.id, transtab, transcfg, > vm->memattr); > + > +out_make_active: > + if (!ret) { > + refcount_set(&vm->as.active_cnt, 1); > + list_del_init(&vm->as.lru_node); > + } > + > +out_unlock: > + mutex_unlock(&ptdev->mmu->as.slots_lock); > + mutex_unlock(&vm->op_lock); > + > +out_dev_exit: > + drm_dev_exit(cookie); > + return ret; > +} > + > + nit: one too many empty lines. > /** > * panthor_mmu_suspend() - Suspend the MMU logic > * @ptdev: Device. > @@ -1805,7 +1808,8 @@ void panthor_mmu_resume(struct panthor_device *ptdev) > ptdev->mmu->as.faulty_mask = 0; > mutex_unlock(&ptdev->mmu->as.slots_lock); > > - panthor_mmu_irq_resume(&ptdev->mmu->irq, panthor_mmu_fault_mask(ptdev, > ~0)); > + panthor_mmu_irq_enable_events(&ptdev->mmu->irq, > panthor_mmu_fault_mask(ptdev, ~0)); I don't think we should touch the events mask in the suspend/resume path. The way I see it, events should be: - enabled when an AS is enabled (as_enable()) - disabled when an AS is disabled (as_disable()) - disabled when a VM has an unhandled faults Because making a VM active might imply evicting another VM, we might end up with disable+enable_events() pairs that we could have been optimized into a NOP, but the overhead should be negligible, and if we have to rotate VMs on AS slots we've already lost anyway (in term of perfs). > + panthor_mmu_irq_resume(&ptdev->mmu->irq); > } > > /** > @@ -1859,7 +1863,8 @@ void panthor_mmu_post_reset(struct panthor_device > *ptdev) > > mutex_unlock(&ptdev->mmu->as.slots_lock); > > - panthor_mmu_irq_resume(&ptdev->mmu->irq, panthor_mmu_fault_mask(ptdev, > ~0)); > + panthor_mmu_irq_enable_events(&ptdev->mmu->irq, > panthor_mmu_fault_mask(ptdev, ~0)); Same here, I don't think we need to change the event mask. > + panthor_mmu_irq_resume(&ptdev->mmu->irq); > > /* Restart the VM_BIND queues. */ > mutex_lock(&ptdev->mmu->vm.lock); > diff --git a/drivers/gpu/drm/panthor/panthor_pwr.c > b/drivers/gpu/drm/panthor/panthor_pwr.c > index 57cfc7ce715b..ed3b2b4479ca 100644 > --- a/drivers/gpu/drm/panthor/panthor_pwr.c > +++ b/drivers/gpu/drm/panthor/panthor_pwr.c > @@ -545,5 +545,5 @@ void panthor_pwr_resume(struct panthor_device *ptdev) > if (!ptdev->pwr) > return; > > - panthor_pwr_irq_resume(&ptdev->pwr->irq, PWR_INTERRUPTS_MASK); > + panthor_pwr_irq_resume(&ptdev->pwr->irq); > } >
