On Tuesday, May 03, 2011, Stephen Boyd wrote:
> On 04/29/2011 03:04 PM, Rafael J. Wysocki wrote:
> > +
> > +/**
> > + * enable_clock - Enable a device clock.
> > + * @dev: Device whose clock is to be enabled.
> > + * @con_id: Connection ID of the clock.
> > + */
> > +static void enable_clock(struct device *dev, const char *con_id)
> > +{
> > + struct clk *clk;
> > +
> > + clk = clk_get(dev, con_id);
> > + if (!IS_ERR(clk)) {
> > + clk_enable(clk);
> > + clk_put(clk);
> > + dev_info(dev, "Runtime PM disabled, clock forced on.\n");
> > + }
> > +}
>
> This doesn't make much sense to me. You're getting a clock and then
> enabling it and then putting the clock? How can you be so sure that
> clk_put() won't one day do some kind of lower power mode on the clock
> when clk_put() is called on it? I don't think anyone does anything
> today, but I don't think its safe to assume that clk_put() won't try to
> forcibly shut off the clock once all clk_get() callers have clk_put().
>
> Perhaps we should document the meaning of clk_enable() followed by
> clk_put() somewhere instead?
That's coming from some existing ARM shmobile code.
There are two alternatives, one not to do any clock management at all
when CONFIG_PM_RUNTIME is unset, the other to remove the "put" from
enable_clock(), but then disable_clock() would need to do "put" twice.
I didn't think any of them was better than the current code.
> > +
> > +/**
> > + * disable_clock - Disable a device clock.
> > + * @dev: Device whose clock is to be disabled.
> > + * @con_id: Connection ID of the clock.
> > + */
> > +static void disable_clock(struct device *dev, const char *con_id)
> > +{
> > + struct clk *clk;
> > +
> > + clk = clk_get(dev, con_id);
> > + if (!IS_ERR(clk)) {
> > + clk_disable(clk);
> > + clk_put(clk);
> > + dev_info(dev, "Runtime PM disabled, clock forced off.\n");
> > + }
> > +}
>
> This might not be as bad, but it looks like a similar problem.
>
> > -
> > -static int platform_bus_notify(struct notifier_block *nb,
> > - unsigned long action, void *data)
> > -{
> > - struct device *dev = data;
> > - struct clk *clk;
> > -
> > - dev_dbg(dev, "platform_bus_notify() %ld !\n", action);
> > -
> > - switch (action) {
> > - case BUS_NOTIFY_BIND_DRIVER:
> > - clk = clk_get(dev, NULL);
> > - if (!IS_ERR(clk)) {
> > - clk_enable(clk);
> > - clk_put(clk);
> > - dev_info(dev, "runtime pm disabled, clock forced on\n");
> > - }
> > - break;
> > - case BUS_NOTIFY_UNBOUND_DRIVER:
> > - clk = clk_get(dev, NULL);
> > - if (!IS_ERR(clk)) {
> > - clk_disable(clk);
> > - clk_put(clk);
> > - dev_info(dev, "runtime pm disabled, clock forced off\n");
> > - }
>
> Ah ok I see that it's coming from here.
Yes, it is.
> BTW, whatever is in linux-next is failing to compile:
>
> drivers/base/power/clock_ops.c:391: error: 'con_id' undeclared (first
> use in this function)
> drivers/base/power/clock_ops.c:391: error: (Each undeclared identifier
> is reported only once
> drivers/base/power/clock_ops.c:391: error: for each function it appears in.)
I guess that's with CONFIG_PM_RUNTIME unset, right?
Sorry about that, the appended patch should fix the issue.
Thanks,
Rafael
---
From: Rafael J. Wysocki <rjw@xxxxxxx>
Subject: PM: Fix build issue in clock_ops.c for CONFIG_PM_RUNTIME unset
Fix a build issue in drivers/base/power/clock_ops.c occuring when
CONFIG_PM_RUNTIME is not set.
Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
drivers/base/power/clock_ops.c | 1 +
1 file changed, 1 insertion(+)
Index: linux-2.6/drivers/base/power/clock_ops.c
===================================================================
--- linux-2.6.orig/drivers/base/power/clock_ops.c
+++ linux-2.6/drivers/base/power/clock_ops.c
@@ -380,6 +380,7 @@ static int pm_runtime_clk_notify(struct
{
struct pm_clk_notifier_block *clknb;
struct device *dev = data;
+ char *con_id;
dev_dbg(dev, "%s() %ld\n", __func__, action);
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