linux-kernel - [PATCH v6 1/6] base: power: runtime: Export pm_runtime_get/put

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Date:   Fri, 19 Jan 2018 17:13:38 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     alex.williamson@...hat.com, robh+dt@...nel.org,
        mark.rutland@....com, rjw@...ysocki.net, robin.murphy@....com,
        will.deacon@....com, iommu@...ts.linux-foundation.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, sboyd@...eaurora.org
Cc:     gregkh@...uxfoundation.org, sricharan@...eaurora.org,
        m.szyprowski@...sung.com, architt@...eaurora.org,
        linux-arm-msm@...r.kernel.org, vivek.gautam@...eaurora.org
Subject: [PATCH v6 1/6] base: power: runtime: Export pm_runtime_get/put_suppliers

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 <vivek.gautam@...eaurora.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 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 6e89b51ea3d9..06a2a88fe866 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)
 {
-- 
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