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Groups > linux.kernel > #1687588
| From | Rob Clark <robdclark@gmail.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH V4 3/6] iommu/arm-smmu: Invoke pm_runtime during probe, add/remove device |
| Date | 2017-07-14 19:50 +0200 |
| Message-ID | <u3cT0-6Is-9@gated-at.bofh.it> (permalink) |
| References | (4 earlier) <u2F10-1tT-7@gated-at.bofh.it> <u2KWK-58b-23@gated-at.bofh.it> <u2MOR-6jw-1@gated-at.bofh.it> <u2NKV-6Wd-1@gated-at.bofh.it> <u3cgi-6qU-15@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Fri, Jul 14, 2017 at 1:07 PM, Will Deacon <will.deacon@arm.com> wrote:
> On Thu, Jul 13, 2017 at 10:55:10AM -0400, Rob Clark wrote:
>> On Thu, Jul 13, 2017 at 9:53 AM, Sricharan R <sricharan@codeaurora.org> wrote:
>> > Hi,
>> >
>> > On 7/13/2017 5:20 PM, Rob Clark wrote:
>> >> On Thu, Jul 13, 2017 at 1:35 AM, Sricharan R <sricharan@codeaurora.org> wrote:
>> >>> Hi Vivek,
>> >>>
>> >>> On 7/13/2017 10:43 AM, Vivek Gautam wrote:
>> >>>> Hi Stephen,
>> >>>>
>> >>>>
>> >>>> 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().
>> >
>> > Ok, with that being the case, there are two things here,
>> >
>> > 1) If the device links are still intact at these places where unmap is called,
>> > then pm_runtime from the master would setup the all the clocks. That would
>> > avoid reintroducing the locking indirectly here.
>> >
>> > 2) If not, then doing it here is the only way. But for both cases, since
>> > the unmap can be called from atomic context, resume handler here should
>> > avoid doing clk_prepare_enable , instead move the clk_prepare to the init.
>> >
>>
>> I do kinda like the approach Marek suggested.. of deferring the tlb
>> flush until resume. I'm wondering if we could combine that with
>> putting the mmu in a stalled state when we suspend (and not resume the
>> mmu until after the pending tlb flush)?
>
> I'm not sure that a stalled state is what we're after here, because we need
> to take care to prevent any table walks if we've freed the underlying pages.
> What we could try to do is disable the SMMU (put into global bypass) and
> invalidate the TLB when performing a suspend operation, then we just ignore
> invalidation whilst the clocks are stopped and, on resume, enable the SMMU
> again.
wouldn't stalled just block any memory transactions by device(s) using
the context bank? Putting it in bypass isn't really a good thing if
there is any chance the device can sneak in a memory access before
we've taking it back out of bypass (ie. makes gpu a giant userspace
controlled root hole).
BR,
-R
> That said, I don't think we can tolerate suspend/resume racing with
> map/unmap, and it's not clear to me how we avoid that without penalising
> the fastpath.
>
> Will
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[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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