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SubjectRe: [PATCH 4/4] mfd: global Suspend and resume support of ehci and ohci
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"Munegowda, Keshava" <keshava_mgowda@ti.com> writes:

> On Wed, Jun 29, 2011 at 8:52 PM, Munegowda, Keshava
> <keshava_mgowda@ti.com> wrote:
>> On Thu, Jun 2, 2011 at 5:36 AM, Kevin Hilman <khilman@ti.com> wrote:
>>> Keshava Munegowda <keshava_mgowda@ti.com> writes:
>>>
>>>> From: Keshava Munegowda <Keshava_mgowda@ti.com>
>>>>
>>>> The global suspend and resume functions for usbhs core driver
>>>> are implemented.These routine are called when the global suspend
>>>> and resume occurs. Before calling these functions, the
>>>> bus suspend and resume of ehci and ohci drivers are called
>>>> from runtime pm.
>>>>
>>>> Signed-off-by: Keshava Munegowda <keshava_mgowda@ti.com>
>>>
>>> First, from what I can see, this is only a partial implementation of
>>> runtime PM.  What I mean is that the runtime PM methods are used only
>>> during the suspend path.  The rest of the time the USB host IP block is
>>> left enabled, even when nothing is connected.
>>>
>>> I tested this on my 3530/Overo board, and verified that indeed the
>>> usbhost powerdomain hits retention on suspend, but while idle, when
>>> nothing is connected, I would expect the driver could be clever enough
>>> to use runtime PM (probably using autosuspend timeouts) to disable the
>>> hardware as well.
>>>
>>>> ---
>>>>  drivers/mfd/omap-usb-host.c |  103 +++++++++++++++++++++++++++++++++++++++++++
>>>>  1 files changed, 103 insertions(+), 0 deletions(-)
>>>>
>>>> diff --git a/drivers/mfd/omap-usb-host.c b/drivers/mfd/omap-usb-host.c
>>>> index 43de12a..32d19e2 100644
>>>> --- a/drivers/mfd/omap-usb-host.c
>>>> +++ b/drivers/mfd/omap-usb-host.c
>>>> @@ -146,6 +146,10 @@
>>>>  #define is_ehci_hsic_mode(x) (x == OMAP_EHCI_PORT_MODE_HSIC)
>>>>
>>>>
>>>> +/* USBHS state bits */
>>>> +#define OMAP_USBHS_INIT              0
>>>> +#define OMAP_USBHS_SUSPEND   4
>>>
>>> These additional state bits don't seem to be necessary.
>>>
>>> For suspend, just check 'pm_runtime_is_suspended()'
>>>
>>> The init flag is only used in the suspend/resume hooks, but the need for
>>> it is a side effect of not correctly using the runtime PM callbacks.
>>>
>>> Remember that the runtime PM get/put hooks have usage counting.  Only
>>> when the usage count transitions to/from zero is the actual
>>> hardware-level enable/disable (via omap_hwmod) being done.
>>>
>>> The current code is making the assumption that every call to get/put is
>>> going to result in an enable/disable of the hardware.
>>>
>>> Instead, all of the code that needs to be run only upon actual
>>> enable/disable of the hardware should be done in the driver's
>>> runtime_suspend/runtime_resume callbacks.  These are only called when
>>> the hardware actually changes state.
>>>
>>> Not knowing that much about the EHCI block, upon first glance, it looks
>>> like mmuch of what is done in usbhs_enable() should actually be done in
>>> the ->runtime_resume() callback, and similarily, much of what is done in
>>> usbhs_disable() should be done in the ->runtime_suspend() callback.
>>
>> Kevin,
>>   do you mean driver->runtime_resume and driver->runtime_resume call backs.
>> are these call backs from pm_runtime_get_sync and pm_runtime_put_sync?
>
> for usb host case , I am seeing that the pm_runtime_get_sync
>
>
> static int rpm_resume(struct device *dev, int rpmflags)
> {
> ............
> ..........
> if (dev->pwr_domain) {
> callback = dev->pwr_domain->ops.runtime_resume;
> if(!strcmp(dev_name(dev),"usbhs_omap"))
> pr_err("dev->pwr_domain->ops.runtime_resume");
> }
> else if (dev->type && dev->type->pm) {
> callback = dev->type->pm->runtime_resume;
> if(!strcmp(dev_name(dev),"usbhs_omap"))
> pr_err("dev->type->pm->runtime_resume");
> }
> else if (dev->class && dev->class->pm) {
> callback = dev->class->pm->runtime_resume;
> if(!strcmp(dev_name(dev),"usbhs_omap"))
> pr_err("ev->class->pm->runtime_resume");
> }
> else if (dev->bus && dev->bus->pm) {
> callback = dev->bus->pm->runtime_resume;
> if(!strcmp(dev_name(dev),"usbhs_omap"))
> pr_err("dev->bus->pm->runtime_resume");
> }
> else
> callback = NULL;
> }
>
>
> I am seeing that below if statement was hitting true:
>
> if (dev->pwr_domain) {
> callback = dev->pwr_domain->ops.runtime_resume;
> if(!strcmp(dev_name(dev),"usbhs_omap"))
> pr_err("dev->pwr_domain->ops.runtime_resume");
>
>
> due to this; the driver->runtime_resume was not getting called.
>
> Any idea on why I am seeing only the dev->pwr_domain is set not
> dev->bus && dev->bus->pm is hitting here?

Because that's how it was designed. :)

On OMAP, for on-chip devices (omap_devices) we use PM domains
(pwr_domain) and not the subsystem (bus) to implment runtime PM, and as
Alan pointed out, PM domains have precedence over subsystem callbacks.

I'm curious why you determined the driver's runtime resume was not
getting called?

The PM domain callback will call your driver's runtime_resume (assuming
it exists.)

rpm_resume()
dev->pwr_domain->ops.runtime_resume()
omap_device_enable()
pm_generic_runtime_resume()
dev->driver->pm->runtime_resume()

Note that the PM domain implementation is done at the omap_device
level. Specifically, see plat-omap/omap_device.c:_od_runtime_resume()

Kevin
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