Hi All,
On 2017-07-13 13:50, Rob Clark wrote:
On Thu, Jul 13, 2017 at 1:35 AM, Sricharan R <sricharan@xxxxxxxxxxxxxx> 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
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