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

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Date:   Fri, 8 Dec 2017 14:21:36 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
Cc:     rjw@...ysocki.net, len.brown@...el.com, pavel@....cz,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        sboyd@...eaurora.org, robdclark@...il.com, robin.murphy@....com,
        will.deacon@....com, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/1] base: power: runtime: Export
 pm_runtime_get/put_suppliers

On Fri, Dec 08, 2017 at 06:00:47PM +0530, Vivek Gautam 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 paths, such as in arm_smmu_unmap.
> 
> [1] https://patchwork.kernel.org/patch/9827825/
> 
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> ---
>  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 027d159ac381..af169304ca13 100644
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -1578,6 +1578,7 @@ void pm_runtime_get_suppliers(struct device *dev)
>  
>  	device_links_read_unlock(idx);
>  }
> +EXPORT_SYMBOL_GPL(pm_runtime_get_suppliers);

We do not export symbols unless there are in-kernel users of them.
Where is the patch that adds a user for these functions?

thanks,

greg k-h