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Date: Thu, 28 Apr 2011 02:58:34 +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, 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?
> > + clk_disable(ce->clk);
> > + ce->clock_enabled = false;
> Clock enables are already refcounted, do you really need a flag as
> well? In what situations would pm_runtime_clk_remove get called,
> which currently needs to know when the clock is enabled?
When the device object is removed, for whatever reason.
> > + }
> > + }
> > +
> > + mutex_unlock(&prd->lock);
> > +
> > + return 0;
> > +}
> > +
> > +/**
> > + * pm_runtime_clk_resume - Enable clocks in a device's runtime PM clock list.
> > + * @dev: Device to enable the clocks for.
> > + */
> > +int pm_runtime_clk_resume(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(ce, &prd->clock_list, node) {
> > + if (!ce->clk)
> > + pm_runtime_clk_acquire(dev, ce);
> If the clock was not present during suspend, should you be enabling it
> during resume?
Because resume is called first as the initial state of the device
is assumed to be RPM_SUSPENDED.
> > +
> > + if (ce->clock_active) {
> > + clk_enable(ce->clk);
> > + ce->clock_enabled = true;
> > + }
> > + }
> > +
> > + mutex_unlock(&prd->lock);
> > +
> > + return 0;
> > +}
HTH,
Rafael
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