linux-kernel - [PATCH v5 1/6] base: power: runtime: Export pm_runtime_get/put

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Message-Id: <1515492109-753-2-git-send-email-vivek.gautam@codeaurora.org>
Date:   Tue,  9 Jan 2018 15:31:44 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     joro@...tes.org, robh+dt@...nel.org, mark.rutland@....com,
        rjw@...ysocki.net, gregkh@...uxfoundation.org, robdclark@...il.com,
        will.deacon@....com, robin.murphy@....com, sboyd@...eaurora.org,
        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
Cc:     len.brown@...el.com, pavel@....cz, airlied@...ux.ie,
        sricharan@...eaurora.org, m.szyprowski@...sung.com,
        architt@...eaurora.org, linux-arm-msm@...r.kernel.org,
        Vivek Gautam <vivek.gautam@...eaurora.org>
Subject: [PATCH v5 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>
---

 * This is v2 of the patch [1]. Adding it to this patch series.
   [1] https://patchwork.kernel.org/patch/10102447/

 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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