linux-kernel - Re: [Update][PATCH 7/9] PM / Runtime: Generic clock manipulation rountines for runtime PM (v3)

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Date:	Thu, 28 Apr 2011 03:06:13 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Colin Cross <ccross@...gle.com>
Cc:	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	Kevin Hilman <khilman@...com>,
	LKML <linux-kernel@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	Len Brown <lenb@...nel.org>, linux-sh@...r.kernel.org,
	lethal@...ux-sh.org, Magnus Damm <magnus.damm@...il.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Greg KH <gregkh@...e.de>
Subject: Re: [Update][PATCH 7/9] PM / Runtime: Generic clock manipulation rountines for runtime PM (v3)

On Thursday, April 28, 2011, Rafael J. Wysocki wrote:
> On Thursday, April 28, 2011, Colin Cross wrote:
> > On Wed, Apr 27, 2011 at 2:48 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > From: Rafael J. Wysocki <rjw@...k.pl>
> > >
> > > Many different platforms and subsystems may want to disable device
> > > clocks during suspend and enable them during resume which is going to
> > > be done in a very similar way in all those cases.  For this reason,
> > > provide generic routines for the manipulation of device clocks during
> > > suspend and resume.
> > >
> > > Convert the ARM shmobile platform to using the new routines.
> > >
> > > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > > ---
> > >
> > > Hi,
> > >
> > > This (hopefully final) version of the patch has a couple of bugs fixed in
> > > clock_ops.c.
> > >
> > > Thanks,
> > > Rafael
> > >
> > > ---
> > >  arch/arm/mach-shmobile/pm_runtime.c |  140 -----------
> > >  drivers/base/power/Makefile         |    1
> > >  drivers/base/power/clock_ops.c      |  423 ++++++++++++++++++++++++++++++++++++
> > >  include/linux/pm_runtime.h          |   42 +++
> > >  kernel/power/Kconfig                |    4
> > >  5 files changed, 479 insertions(+), 131 deletions(-)
> > >
> > <snip>
> > > +void pm_runtime_clk_remove(struct device *dev, const char *con_id)
> > > +{
> > > +       struct pm_runtime_clk_data *prd = __to_prd(dev);
> > > +       struct pm_clock_entry *ce;
> > > +
> > > +       if (!prd)
> > > +               return;
> > > +
> > > +       mutex_lock(&prd->lock);
> > > +
> > > +       list_for_each_entry(ce, &prd->clock_list, node)
> > Braces
> 
> No, this is correct as is.
> 
> > > +               if (!con_id && !ce->con_id) {
> > > +                       __pm_runtime_clk_remove(ce);
> > > +                       break;
> > > +               } else if (!con_id || !ce->con_id) {
> > > +                       continue;
> > > +               } else if (!strcmp(con_id, ce->con_id)) {
> > > +                       __pm_runtime_clk_remove(ce);
> > > +                       break;
> > > +               }
> > > +
> > > +       mutex_unlock(&prd->lock);
> > > +}
> > >
> > > +/**
> > > + * pm_runtime_clk_acquire - Acquire a device clock.
> > > + * @dev: Device whose clock is to be acquired.
> > > + * @con_id: Connection ID of the clock.
> > > + */
> > > +static void pm_runtime_clk_acquire(struct device *dev,
> > > +                                   struct pm_clock_entry *ce)
> > > +{
> > > +       ce->clk = clk_get(dev, ce->con_id);
> > > +       if (!IS_ERR(ce->clk)) {
> > > +               ce->clock_active = true;
> > > +               dev_dbg(dev, "Clock %s managed by runtime PM.\n", ce->con_id);
> > > +       }
> > > +}
> > > +
> > > +/**
> > > + * pm_runtime_clk_suspend - Disable clocks in a device's runtime PM clock list.
> > > + * @dev: Device to disable the clocks for.
> > > + */
> > > +int pm_runtime_clk_suspend(struct device *dev)
> > > +{
> > > +       struct pm_runtime_clk_data *prd = __to_prd(dev);
> > > +       struct pm_clock_entry *ce;
> > > +
> > > +       dev_dbg(dev, "%s()\n", __func__);
> > > +
> > > +       if (!prd)
> > > +               return 0;
> > > +
> > > +       mutex_lock(&prd->lock);
> > > +
> > > +       list_for_each_entry_reverse(ce, &prd->clock_list, node) {
> > > +               if (!ce->clk) {
> > > +                       dev_err(dev, "Clock is not ready for runtime PM\n");
> > > +                       pm_runtime_clk_acquire(dev, ce);
> > Why delay the call to clk_get until the first suspend?
> 
> Because the clock framework need not be ready at the _add time.
> 
> > Also, this will always print an error during the first call to suspend.
> 
> That actually depends on the initial state of the device and the
> assumption is that will be RPM_SUSPENDED, so _resume will be called
> first.
> 
> I can remove the message, but it's there for backwards compatibility with
> the code this is intended to replace.
> 
> > > +               }
> > > +
> > > +               if (ce->clock_active) {
> > I don't think clock_active is necessary, and the name is misleading.
> 
> It's not strictly necessary and "active" means "being used for runtime PM".
> 
> > Why not use if (ce->clk)?
> 
> Because _that_ would be confusing?

Moreover, if the first clk_get() fails, this avoids repeating it
during every suspend/resume (because it most probably is going to fail too).

Thanks,
Rafael
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