Messages in this thread | | | Subject | Re: [PATCH v12 3/4] iommu/arm-smmu: Add the device_link between masters and smmu | From | Vivek Gautam <> | Date | Wed, 11 Jul 2018 16:06:14 +0530 |
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Hi Rafael,
On 7/11/2018 3:23 PM, Rafael J. Wysocki wrote: > On Sunday, July 8, 2018 7:34:12 PM CEST Vivek Gautam wrote: >> From: Sricharan R <sricharan@codeaurora.org> >> >> Finally add the device link between the master device and >> smmu, so that the smmu gets runtime enabled/disabled only when the >> master needs it. This is done from add_device callback which gets >> called once when the master is added to the smmu. >> >> Signed-off-by: Sricharan R <sricharan@codeaurora.org> >> Signed-off-by: Vivek Gautam <vivek.gautam@codeaurora.org> >> Reviewed-by: Tomasz Figa <tfiga@chromium.org> >> Cc: Rafael J. Wysocki <rjw@rjwysocki.net> >> Cc: Lukas Wunner <lukas@wunner.de> >> --- >> >> - Change since v11 >> * Replaced DL_FLAG_AUTOREMOVE flag with DL_FLAG_AUTOREMOVE_SUPPLIER. >> >> drivers/iommu/arm-smmu.c | 12 ++++++++++++ >> 1 file changed, 12 insertions(+) >> >> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c >> index 09265e206e2d..916cde4954d2 100644 >> --- a/drivers/iommu/arm-smmu.c >> +++ b/drivers/iommu/arm-smmu.c >> @@ -1461,8 +1461,20 @@ static int arm_smmu_add_device(struct device *dev) >> >> iommu_device_link(&smmu->iommu, dev); >> >> + if (pm_runtime_enabled(smmu->dev) && > Why does the creation of the link depend on whether or not runtime PM > is enabled for the MMU device?
The main purpose of this device link is to handle the runtime PM synchronization between the supplier (iommu) and consumer (client devices, such as GPU/display). Moreover, the runtime pm is conditionally enabled for smmu devices that support such [1]. > > What about system-wide PM and system shutdown? Are they always guaranteed > to happen in the right order without the link?
When there's no runtime PM, there's no clocks, and other resources to be handled. So, we don't need device link for system-wide PM and system shutdown to work correctly. That's the case with current arm-smmu driver. Is it something that i am missing here?
[1] https://lkml.org/lkml/2018/3/8/775
Thanks Vivek >> + !device_link_add(dev, smmu->dev, >> + DL_FLAG_PM_RUNTIME | DL_FLAG_AUTOREMOVE_SUPPLIER)) { >> + dev_err(smmu->dev, "Unable to add link to the consumer %s\n", >> + dev_name(dev)); >> + ret = -ENODEV; >> + goto out_unlink; >> + } >> + >> return 0; >> >> +out_unlink: >> + iommu_device_unlink(&smmu->iommu, dev); >> + arm_smmu_master_free_smes(fwspec); >> out_cfg_free: >> kfree(cfg); >> out_free: >> >
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