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

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Date:   Fri, 12 Jan 2018 11:17:33 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Joerg Roedel <joro@...tes.org>, Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Clark <robdclark@...il.com>,
        Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        "open list:AMD IOMMU (AMD-VI)" <iommu@...ts.linux-foundation.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        freedreno@...ts.freedesktop.org, Len Brown <len.brown@...el.com>,
        Pavel Machek <pavel@....cz>, David Airlie <airlied@...ux.ie>,
        Sricharan R <sricharan@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        architt@...eaurora.org,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>
Subject: Re: [PATCH v5 1/6] base: power: runtime: Export
 pm_runtime_get/put_suppliers



On 01/12/2018 04:23 AM, Rafael J. Wysocki wrote:
> On Tue, Jan 9, 2018 at 11:01 AM, Vivek Gautam
> <vivek.gautam@...eaurora.org> wrote:
>> 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>
>
> Please feel free to route this along with the rest of the series.

Thanks Rafael.

regards
Vivek

>
> Thanks!
>
>> ---
>>
>>   * 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)
>>   {
>> --
>> 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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