linux-kernel - Re: [PATCH 1/7] PM / Domains: Make it possible to use per-device start/stop routines

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Date:	Tue, 8 Nov 2011 10:30:38 +0100 (CET)
From:	Guennadi Liakhovetski <g.liakhovetski@....de>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
cc:	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>,
	Kevin Hilman <khilman@...com>, jean.pihet@...oldbits.com
Subject: Re: [PATCH 1/7] PM / Domains: Make it possible to use per-device
 start/stop routines

Hi Rafael

On Mon, 7 Nov 2011, Rafael J. Wysocki wrote:

> From: Rafael J. Wysocki <rjw@...k.pl>
> 
> The current generic PM domains code requires that the same .stop()
> and .start() device callback routines be used for all devices in the
> given domain, which is inflexible and may not cover some specific use
> cases.  For this reason, make it possible to use device specific
> .start() and .stop() callback routines by adding corresponding
> callback pointers to struct generic_pm_domain_data.  Add a new helper
> routine, pm_genpd_register_callbacks(), that can be used to populate
> the new per-device callback pointers.
> 
> Modify the shmobile's power domains code to allow drivers to add
> their own code to be run during the device stop and start operations
> with the help of the new callback pointers.
> 
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> ---

[snip]

> Index: linux/drivers/base/power/domain.c
> ===================================================================
> --- linux.orig/drivers/base/power/domain.c
> +++ linux/drivers/base/power/domain.c
> @@ -29,6 +29,36 @@ static struct generic_pm_domain *dev_to_
>  	return pd_to_genpd(dev->pm_domain);
>  }
>  
> +static int genpd_stop_dev(struct generic_pm_domain *genpd, struct device *dev)
> +{
> +	int (*stop)(struct device *dev);
> +
> +	stop = genpd->stop_device;
> +	if (stop)
> +		return stop(dev);
> +
> +	stop = dev_gpd_data(dev)->ops.stop;
> +	if (stop)
> +		return stop(dev);

With this implementation your approach is: in your genpd_stop_dev() and 
genpd_start_dev() you first check for the pm-domain _common_ .start() and 
.stop(), and if they exist, the specific ones will not be called. Then in 
your sh7372 pm domain implementation you do the domain-common part - 
switch the PM clock on or off, and you _again_ check for device-specific 
domains, and this time you call both of them.

Do you have specific reasons to think, that calling both of them from 
genpd_stop_dev() / genpd_start_dev() might not fit some PM-domain 
implementations?

Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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