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From:   Vivek Gautam <vivek.gautam@codeaurora.org>
To:     joro@8bytes.org, robh+dt@kernel.org, mark.rutland@arm.com,
        rjw@rjwysocki.net, robin.murphy@arm.com, will.deacon@arm.com,
        robdclark@gmail.com, iommu@lists.linux-foundation.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-pm@vger.kernel.org, dri-devel@lists.freedesktop.org,
        freedreno@lists.freedesktop.org
Cc:     alex.williamson@redhat.com, gregkh@linuxfoundation.org,
        airlied@linux.ie, sboyd@codeaurora.org, sricharan@codeaurora.org,
        m.szyprowski@samsung.com, architt@codeaurora.org,
        linux-arm-msm@vger.kernel.org, vivek.gautam@codeaurora.org
Subject: [PATCH v7 1/6] base: power: runtime: Export pm_runtime_get/put_suppliers
Date:   Wed,  7 Feb 2018 16:01:17 +0530
Message-Id: <1517999482-17317-2-git-send-email-vivek.gautam@codeaurora.org>
In-Reply-To: <1517999482-17317-1-git-send-email-vivek.gautam@codeaurora.org>
References: <1517999482-17317-1-git-send-email-vivek.gautam@codeaurora.org>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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@codeaurora.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.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 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)
 {
-- 
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