On Fri, Dec 8, 2017 at 7:37 PM, Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote: > On Fri, Dec 8, 2017 at 2:39 PM, Vivek Gautam > <vivek.gautam@xxxxxxxxxxxxxx> wrote: >> Hi Greg, >> >> >> On Fri, Dec 8, 2017 at 6:51 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote: >>> On Fri, Dec 08, 2017 at 06:00:47PM +0530, Vivek Gautam wrote: >>>> The device link allows the pm framework to tie the supplier and >>>> consumer. So, whenever the consumer is powered-on, the supplier >>>> is powered-on first. >>>> >>>> There are however cases in which the consumer wants to power-on >>>> the supplier, but not itself. >>>> E.g., A Graphics or multimedia driver wants to power-on the SMMU >>>> to unmap a buffer and finish the TLB operations without powering >>>> on itself. Some of these unmap requests are coming from the >>>> user space when the controller itself is not powered-up, and it >>>> can be huge penalty in terms of power and latency to power-up >>>> the graphics/mm controllers. >>>> There can be an argument that the supplier should handle this case >>>> on its own and there should not be a need for the consumer to >>>> power-on the supplier. But as discussed on the thread [1] about >>>> ARM-SMMU runtime pm, we don't want to introduce runtime pm calls >>>> in atomic paths, such as in arm_smmu_unmap. >>>> >>>> [1] https://patchwork.kernel.org/patch/9827825/ >>>> >>>> Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx> >>>> --- >>>> drivers/base/power/runtime.c | 2 ++ >>>> 1 file changed, 2 insertions(+) >>>> >>>> diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c >>>> index 027d159ac381..af169304ca13 100644 >>>> --- a/drivers/base/power/runtime.c >>>> +++ b/drivers/base/power/runtime.c >>>> @@ -1578,6 +1578,7 @@ void pm_runtime_get_suppliers(struct device *dev) >>>> >>>> device_links_read_unlock(idx); >>>> } >>>> +EXPORT_SYMBOL_GPL(pm_runtime_get_suppliers); >>> >>> We do not export symbols unless there are in-kernel users of them. >>> Where is the patch that adds a user for these functions? >> >> My apologies for not putting the changes for the user of these APIs. >> I will be sending a patch for the user (which would be: >> "drivers/gpu/drm/msm/msm_iommu.c"). The patch will be included >> with the arm-smmu runtime patch series. Right now I am facing issues >> with the use of clk_bulk_*() APIs on 4.15-rc kernel. >> >> But, I wanted to get opinions about this change since we had been >> discussing about this in the arm-smmu runtime patch thread [1]. >> >> [1] https://patchwork.kernel.org/patch/9827825/ >> >> >> P.S.: A snippet of the change in the user of these APIs: >> >> 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 >> @@ -76,9 +76,9 @@ static int msm_iommu_unmap(struct msm_mmu *mmu, >> uint64_t iova, >> { >> struct msm_iommu *iommu = to_msm_iommu(mmu); >> >> - pm_runtime_get_sync(mmu->dev); >> + pm_runtime_get_suppliers(mmu->dev); >> iommu_unmap(iommu->domain, iova, len); >> - pm_runtime_put_sync(mmu->dev); >> + pm_runtime_put_suppliers(mmu->dev); >> >> return 0; >> } >> > > Well, pm_runtime_get/put_suppliers() were not designed to be used > outside of the runtime PM core code. I need to have a deeper look > into things at this point, so give me some time. Thanks Rafael. regards Vivek > > Thanks, > Rafael > -- > 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 linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
