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Date: Thu, 25 Mar 2010 09:57:20 +0100
From: Jean Delvare <khali@...ux-fr.org>
To: "Rafael J. Wysocki" <rjw@...k.pl>,
Mark Brown <broonie@...nsource.wolfsonmicro.com>
Cc: linux-pm@...ts.linux-foundation.org,
Linux I2C <linux-i2c@...r.kernel.org>,
Alan Stern <stern@...land.harvard.edu>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: Fix bus-level power management callbacks
Hi Rafael,
On Fri, 19 Mar 2010 23:44:08 +0100, Rafael J. Wysocki wrote:
> I assume the lack of responses except for the Alan's one means the patch
> wasn't correct, so below is one that I think is better. It fixes all of the
> issues described above without breaking backwards compatibility.
>
> Thanks,
> Rafael
>
> ---
> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: i2c: Fix bus-level power management callbacks
>
> There are three issues with the i2c bus type's power management
> callbacks at the moment. First, they don't include any hibernate
> callbacks, although they should at least include the .restore()
> callback (there's no guarantee that the driver will be present in
> memory before loading the image kernel and we must restore the
> pre-hibernation state of the device). Second, the "legacy"
> callbacks are not going to be invoked by the PM core since the bus
> type's pm object is not NULL. Finally, the system sleep PM
> (ie. suspend/resume) callbacks don't check if the device has been
> already suspended at run time, in which case they should skip
> suspending it. Also, it looks like the i2c bus type can use the
> generic subsystem-level runtime PM callbacks.
>
> For these reasons, rework the system sleep PM callbacks provided by
> the i2c bus type to handle hibernation correctly and to invoke the
> "legacy" callbacks for drivers that provide them. In addition to
> that make the i2c bus type use the generic subsystem-level runtime
> PM callbacks.
>
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
Mark, you contributed the initial runtime PM support for the i2c
subsystem, I thought you would have comments on Rafael's
reimplementation?
> ---
> drivers/i2c/i2c-core.c | 168 ++++++++++++++++++++++++++-------------------
> include/linux/pm_runtime.h | 7 +
I am a little surprised to see changes to a generic header file here,
how is the i2c subsystem so special that we have needs other subsystems
did not?
> 2 files changed, 105 insertions(+), 70 deletions(-)
>
> Index: linux-2.6/drivers/i2c/i2c-core.c
> ===================================================================
> --- linux-2.6.orig/drivers/i2c/i2c-core.c
> +++ linux-2.6/drivers/i2c/i2c-core.c
> @@ -156,107 +156,131 @@ static void i2c_device_shutdown(struct d
> driver->shutdown(client);
> }
>
> -#ifdef CONFIG_SUSPEND
> -static int i2c_device_pm_suspend(struct device *dev)
> +static int i2c_legacy_suspend(struct device *dev, pm_message_t mesg)
> {
> - const struct dev_pm_ops *pm;
> + struct i2c_client *client = i2c_verify_client(dev);
> + struct i2c_driver *driver;
>
> - if (!dev->driver)
> + if (!client || !dev->driver)
> return 0;
> - pm = dev->driver->pm;
> - if (!pm || !pm->suspend)
> + driver = to_i2c_driver(dev->driver);
> + if (!driver->suspend)
> return 0;
> - return pm->suspend(dev);
> + return driver->suspend(client, mesg);
> }
>
> -static int i2c_device_pm_resume(struct device *dev)
> +static int i2c_legacy_resume(struct device *dev)
> {
> - const struct dev_pm_ops *pm;
> + struct i2c_client *client = i2c_verify_client(dev);
> + struct i2c_driver *driver;
>
> - if (!dev->driver)
> + if (!client || !dev->driver)
> return 0;
> - pm = dev->driver->pm;
> - if (!pm || !pm->resume)
> + driver = to_i2c_driver(dev->driver);
> + if (!driver->resume)
> return 0;
> - return pm->resume(dev);
> + return driver->resume(client);
> }
> -#else
> -#define i2c_device_pm_suspend NULL
> -#define i2c_device_pm_resume NULL
> -#endif
I fail to see why the functions above are outside of the #ifdef
CONFIG_PM_SLEEP scope. They are only called by functions which are
inside the #ifdef CONFIG_PM_SLEEP scope, so you'll get a build-time
warning if CONFIG_PM_SLEEP isn't set.
Is there a plan to get rid of the above legacy functions at some point
in time?
>
> -#ifdef CONFIG_PM_RUNTIME
> -static int i2c_device_runtime_suspend(struct device *dev)
> +#ifdef CONFIG_PM_SLEEP
> +static int i2c_device_pm_suspend(struct device *dev)
> {
> - const struct dev_pm_ops *pm;
> + const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>
> - if (!dev->driver)
> - return 0;
> - pm = dev->driver->pm;
> - if (!pm || !pm->runtime_suspend)
> + if (pm_runtime_suspended(dev))
> return 0;
> - return pm->runtime_suspend(dev);
> -}
> (...)
Apart from the above, the code looks sane to me, but then again I don't
know a thing about power management. I'll keep this patch in my i2c
tree, scheduled for merge in 2.6.35. If there are any updates, please
send them over, either as a new patch or as incremental changes which I
will merge myself.
--
Jean Delvare
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