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Groups > linux.kernel > #1686500
| From | Marek Szyprowski <m.szyprowski@samsung.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device |
| Date | 2017-07-13 14:30 +0200 |
| Message-ID | <u2LpM-5AM-19@gated-at.bofh.it> (permalink) |
| References | (4 earlier) <u2F10-1tT-7@gated-at.bofh.it> <u2L6q-5tf-23@gated-at.bofh.it> <u2KWK-58b-23@gated-at.bofh.it> <u2L6q-5tf-21@gated-at.bofh.it> <u2Lg7-5xB-23@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Hi Rob,
On 2017-07-13 14:10, Rob Clark wrote:
> On Thu, Jul 13, 2017 at 8:02 AM, Marek Szyprowski
> <m.szyprowski@samsung.com> wrote:
>> 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.
>>
> that seems like an interesting approach.. although I wonder if there
> can be some race w/ new device memory access once clks are enabled
> before tlb flush completes? That would be rather bad, since this
> approach is letting the backing pages of memory be freed before tlb
> flush.
Exynos IOMMU has spinlock for ensuring that there is no race between PM
runtime
suspend and unmap/tlb flush.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
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[PATCH V4 0/6] iommu/arm-smmu: Add runtime pm/sleep support Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-06 11:40 +0200
[PATCH V4 2/6] iommu/arm-smmu: Add pm_runtime/sleep ops Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-06 11:40 +0200
Re: [PATCH V4 2/6] iommu/arm-smmu: Add pm_runtime/sleep ops Stephen Boyd <sboyd@codeaurora.org> - 2017-07-13 01:00 +0200
Re: [PATCH V4 2/6] iommu/arm-smmu: Add pm_runtime/sleep ops Stephen Boyd <sboyd@codeaurora.org> - 2017-07-13 01:10 +0200
Re: [PATCH V4 2/6] iommu/arm-smmu: Add pm_runtime/sleep ops Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-13 06:00 +0200
[PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-06 11:40 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Stephen Boyd <sboyd@codeaurora.org> - 2017-07-13 01:00 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-13 07:20 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Sricharan R <sricharan@codeaurora.org> - 2017-07-13 07:40 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-13 14:00 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Marek Szyprowski <m.szyprowski@samsung.com> - 2017-07-13 14:10 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-13 14:20 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Marek Szyprowski <m.szyprowski@samsung.com> - 2017-07-13 14:30 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Sricharan R <sricharan@codeaurora.org> - 2017-07-13 16:00 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-13 17:00 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Will Deacon <will.deacon@arm.com> - 2017-07-14 19:10 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-14 19:50 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Will Deacon <will.deacon@arm.com> - 2017-07-14 20:10 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-14 20:30 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Will Deacon <will.deacon@arm.com> - 2017-07-14 21:10 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-14 21:40 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Sricharan R <sricharan@codeaurora.org> - 2017-07-17 13:50 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Sricharan R <sricharan@codeaurora.org> - 2017-07-17 14:30 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Will Deacon <will.deacon@arm.com> - 2017-07-14 21:40 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-14 21:40 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-13 16:00 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-13 16:10 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Stephen Boyd <sboyd@codeaurora.org> - 2017-07-13 08:50 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Robin Murphy <robin.murphy@arm.com> - 2017-07-13 12:00 +0200
Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device Rob Clark <robdclark@gmail.com> - 2017-07-13 14:00 +0200
[PATCH V4 4/6] iommu/arm-smmu: Add the device_link between masters and smmu Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-06 11:40 +0200
Re: [PATCH V4 4/6] iommu/arm-smmu: Add the device_link between masters and smmu Stephen Boyd <sboyd@codeaurora.org> - 2017-07-13 01:00 +0200
Re: [PATCH V4 4/6] iommu/arm-smmu: Add the device_link between masters and smmu Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-13 06:00 +0200
[PATCH V4 5/6] iommu/arm-smmu: Add support for MMU40x/500 clocks Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-06 11:40 +0200
Re: [PATCH V4 5/6] iommu/arm-smmu: Add support for MMU40x/500 clocks Rob Herring <robh@kernel.org> - 2017-07-10 05:40 +0200
Re: [PATCH V4 5/6] iommu/arm-smmu: Add support for MMU40x/500 clocks Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-11 07:20 +0200
[PATCH V4 6/6] iommu/arm-smmu: Add support for qcom,msm8996-smmu-v2 clocks Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-06 11:40 +0200
Re: [PATCH V4 6/6] iommu/arm-smmu: Add support for qcom,msm8996-smmu-v2 clocks Rob Herring <robh@kernel.org> - 2017-07-10 05:50 +0200
Re: [PATCH V4 6/6] iommu/arm-smmu: Add support for qcom,msm8996-smmu-v2 clocks Vivek Gautam <vivek.gautam@codeaurora.org> - 2017-07-10 08:50 +0200
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