Hi Tomasz, On Wed, Feb 14, 2018 at 8:31 AM, Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: > On Wed, Feb 14, 2018 at 11:13 AM, Rob Clark <robdclark@xxxxxxxxx> wrote: >> On Tue, Feb 13, 2018 at 8:59 PM, Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: >>> On Wed, Feb 14, 2018 at 3:03 AM, Rob Clark <robdclark@xxxxxxxxx> wrote: >>>> On Tue, Feb 13, 2018 at 4:10 AM, Tomasz Figa <tfiga@xxxxxxxxxxxx> wrote: >>>>> Hi Vivek, >>>>> >>>>> Thanks for the patch. Please see my comments inline. >>>>> >>>>> On Wed, Feb 7, 2018 at 7:31 PM, Vivek Gautam >>>>> <vivek.gautam@xxxxxxxxxxxxxx> wrote: >>>>>> While handling the concerned iommu, there should not be a >>>>>> need to power control the drm devices from iommu interface. >>>>>> If these drm devices need to be powered around this time, >>>>>> the respective drivers should take care of this. >>>>>> >>>>>> Replace the pm_runtime_get/put_sync(<drm_device>) with >>>>>> pm_runtime_get/put_suppliers(<drm_device>) calls, to power-up >>>>>> the connected iommu through the device link interface. >>>>>> In case the device link is not setup these get/put_suppliers() >>>>>> calls will be a no-op, and the iommu driver should take care of >>>>>> powering on its devices accordingly. >>>>>> >>>>>> Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx> >>>>>> --- >>>>>> drivers/gpu/drm/msm/msm_iommu.c | 16 ++++++++-------- >>>>>> 1 file changed, 8 insertions(+), 8 deletions(-) >>>>>> >>>>>> diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c >>>>>> index b23d33622f37..1ab629bbee69 100644 >>>>>> --- a/drivers/gpu/drm/msm/msm_iommu.c >>>>>> +++ b/drivers/gpu/drm/msm/msm_iommu.c >>>>>> @@ -40,9 +40,9 @@ static int msm_iommu_attach(struct msm_mmu *mmu, const char * const *names, >>>>>> struct msm_iommu *iommu = to_msm_iommu(mmu); >>>>>> int ret; >>>>>> >>>>>> - pm_runtime_get_sync(mmu->dev); >>>>>> + pm_runtime_get_suppliers(mmu->dev); >>>>>> ret = iommu_attach_device(iommu->domain, mmu->dev); >>>>>> - pm_runtime_put_sync(mmu->dev); >>>>>> + pm_runtime_put_suppliers(mmu->dev); >>>>> >>>>> For me, it looks like a wrong place to handle runtime PM of IOMMU >>>>> here. iommu_attach_device() calls into IOMMU driver's attach_device() >>>>> callback and that's where necessary runtime PM gets should happen, if >>>>> any. In other words, driver A (MSM DRM driver) shouldn't be dealing >>>>> with power state of device controlled by driver B (ARM SMMU). >>>> >>>> Note that we end up having to do the same, because of iommu_unmap() >>>> while DRM driver is powered off.. it might be cleaner if it was all >>>> self contained in the iommu driver, but that would make it so other >>>> drivers couldn't call iommu_unmap() from an irq handler, which is >>>> apparently something that some of them want to do.. >>> >>> I'd assume that runtime PM status is already guaranteed to be active >>> when the IRQ handler is running, by some other means (e.g. >>> pm_runtime_get_sync() called earlier, when queuing some work to the >>> hardware). Otherwise, I'm not sure how a powered down device could >>> trigger an IRQ. >>> >>> So, if the master device power is already on, suppliers should be >>> powered on as well, thanks to device links. >>> >> >> umm, that is kindof the inverse of the problem.. the problem is >> things like gpu driver (and v4l2 drivers that import dma-buf's, >> afaict).. they will potentially call iommu->unmap() when device is not >> active (due to userspace or things beyond the control of the driver).. >> so *they* would want iommu to do pm get/put calls. > > Which is fine and which is actually already done by one of the patches > in this series, not for map/unmap, but probe, add_device, > remove_device. Having parts of the API doing it inside the callback > and other parts outside sounds at least inconsistent. > >> But other drivers >> trying to unmap from irq ctx would not. Which is the contradictory >> requirement that lead to the idea of iommu user powering up iommu for >> unmap. > > Sorry, maybe I wasn't clear. My last message was supposed to show that > it's not contradictory at all, because "other drivers trying to unmap > from irq ctx" would already have called pm_runtime_get_*() earlier > from a non-irq ctx, which would have also done the same on all the > linked suppliers, including the IOMMU. The ultimate result would be > that the map/unmap() of the IOMMU driver calling pm_runtime_get_sync() > would do nothing besides incrementing the reference count. The entire point was to avoid the slowpath that pm_runtime_get/put_sync() would add in map/unmap. It would not be correct to add a slowpath in irq_ctx for taking care of non-irq_ctx and for the situations where master is already powered-off. > >> >> There has already been some discussion about this on various earlier >> permutations of this patchset. I think we have exhausted all other >> options. > > I guess I should have read those. Let me do that now. Yea, i point to the thread in cover letter and [PATCH 1/6]. Thanks. regards Vivek > > Best regards, > Tomasz > -- > To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
