Messages in this thread | | | Subject | Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device | From | Marek Szyprowski <> | Date | Thu, 13 Jul 2017 14:02:40 +0200 |
| |
Hi All,
On 2017-07-13 13:50, Rob Clark wrote: > On Thu, Jul 13, 2017 at 1:35 AM, Sricharan R <sricharan@codeaurora.org> wrote: >> On 7/13/2017 10:43 AM, Vivek Gautam wrote: >>> On 07/13/2017 04:24 AM, Stephen Boyd wrote: >>>> On 07/06, Vivek Gautam wrote: >>>>> @@ -1231,12 +1237,18 @@ static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova, >>>>> static size_t arm_smmu_unmap(struct iommu_domain *domain, unsigned long iova, >>>>> size_t size) >>>>> { >>>>> - struct io_pgtable_ops *ops = to_smmu_domain(domain)->pgtbl_ops; >>>>> + struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain); >>>>> + struct io_pgtable_ops *ops = smmu_domain->pgtbl_ops; >>>>> + size_t ret; >>>>> if (!ops) >>>>> return 0; >>>>> - return ops->unmap(ops, iova, size); >>>>> + pm_runtime_get_sync(smmu_domain->smmu->dev); >>>> Can these map/unmap ops be called from an atomic context? I seem >>>> to recall that being a problem before. >>> That's something which was dropped in the following patch merged in master: >>> 523d7423e21b iommu/arm-smmu: Remove io-pgtable spinlock >>> >>> Looks like we don't need locks here anymore? >> Apart from the locking, wonder why a explicit pm_runtime is needed >> from unmap. Somehow looks like some path in the master using that >> should have enabled the pm ? >> > Yes, there are a bunch of scenarios where unmap can happen with > disabled master (but not in atomic context). On the gpu side we > opportunistically keep a buffer mapping until the buffer is freed > (which can happen after gpu is disabled). Likewise, v4l2 won't unmap > an exported dmabuf while some other driver holds a reference to it > (which can be dropped when the v4l2 device is suspended). > > Since unmap triggers tbl flush which touches iommu regs, the iommu > driver *definitely* needs a pm_runtime_get_sync().
Afair unmap might be called from atomic context as well, for example as a result of dma_unmap_page(). In exynos IOMMU I simply check the runtime PM state of IOMMU device. TLB flush is performed only when IOMMU is in active state. If it is suspended, I assume that the IOMMU controller's context is already lost and its respective power domain might be already turned off, so there is no point in touching IOMMU registers.
Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
| |