Re: [PATCH v5 07/14] drm/panthor: Add the MMU/VM logical block

[Boris Brezillon <boris.brezillon@collabora.com>]

On Sun, 18 Feb 2024 22:41:21 +0100
Boris Brezillon <boris.brezillon@collabora.com> wrote:

> +int panthor_vm_active(struct panthor_vm *vm)
> +{
> +	struct panthor_device *ptdev = vm->ptdev;
> +	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;
> +
> +	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;
> +		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;

We also need

		   AS_TRANSCFG_INA_BITS(55 - va_bits);

otherwise we lack one page table level on 32-bit platforms where the
virtual address space is artificially limited to 32bits.


> +	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);
> +		gpu_write(ptdev, MMU_INT_MASK, ~ptdev->mmu->as.faulty_mask);
> +	}
> +
> +	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);
> +
> +out_dev_exit:
> +	drm_dev_exit(cookie);
> +	return ret;
> +}