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 path in arm_smmu_unmap.

[1] https://patchwork.kernel.org/patch/9827825/

Signed-off-by: Vivek Gautam <redacted>
Acked-by: Rafael J. Wysocki <redacted>
---
 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 8bef3cb2424d..5b8226c8af19 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c

@@ -1579,6 +1579,7 @@ void pm_runtime_get_suppliers(struct device *dev)
 
 	device_links_read_unlock(idx);
 }
+EXPORT_SYMBOL_GPL(pm_runtime_get_suppliers);
 
 /**
  * pm_runtime_put_suppliers - Drop references to supplier devices.

@@ -1597,6 +1598,7 @@ void pm_runtime_put_suppliers(struct device *dev)
 
 	device_links_read_unlock(idx);
 }
+EXPORT_SYMBOL_GPL(pm_runtime_put_suppliers);
 
 void pm_runtime_new_link(struct device *dev)
 {

-- 
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation

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