Hi Rafael,


On Wed, Jul 11, 2018 at 4:06 PM, Vivek Gautam
[off-list ref] wrote:

Hi Rafael,



On 7/11/2018 3:23 PM, Rafael J. Wysocki wrote:

quoted

On Sunday, July 8, 2018 7:34:12 PM CEST Vivek Gautam wrote:

quoted

From: Sricharan R <redacted>

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 <redacted>
Signed-off-by: Vivek Gautam <redacted>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Cc: Rafael J. Wysocki <redacted>
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].

Is there something you would like me to modify in this patch?

Best regards
Vivek

quoted

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

quoted

quoted

+           !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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