On 11/14/2013 04:25 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 16:12 +0800, mike wrote:
On 11/14/2013 03:53 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 15:19 +0800, mike wrote:
On 11/14/2013 01:59 PM, Huang Ying wrote:
On Thu, 2013-11-14 at 11:23 +0800, mike wrote:
On 11/14/2013 03:20 AM, Alan Stern wrote:
On Wed, 13 Nov 2013, Bjorn Helgaas wrote:
[+cc Rafael, linux-pm]
On Wed, Nov 13, 2013 at 6:09 AM, mike<qiudayu@xxxxxxxxxxxxxxxxxx> wrote:
Hi Huang Ying,
I see you are the author of this patch, commit id is:
967577b062417b4e4b8e27b711220f4124f5153a
I have a question while I try to understand this patch,
So I would very grateful if you or others can give me some reply.....
............
- rc = ddi->drv->probe(ddi->dev, ddi->id);
+ pm_runtime_get_sync(dev);
+ pci_dev->driver = pci_drv;
^^^^^^^^^^^^^^^^^^^^^^^^^^
I see here you make the driver to initialize before probe,
But I have no idea of why you do this change.....
and I look inside the code, it may be pm_runtime relate??
Yes, it is related to runtime PM. In the PCI subsystem, runtime PM
doesn't do anything unless pci_dev->driver is set. You can see this at
the start of pci_pm_runtime_suspend().
Since we want the driver's probe routine to be able to carry out
runtime PM operations, we have to set pci_dev->driver before the probe
routine runs.
Is there any situations , like in probe state, pci_dev->driver
has been set. the pci_pm_runtime_xxx() has passed
pci_dev->driver NULL check, but at this point, probe fail
occurs, and pci_dev->driver to be set to NULL.
What will happen ? Or this situation will never happen?
I'm confuse about this.
I think that will never happen. Before ->probe(), pm_runtime_get_sync()
is called, so pci_pm_runtime_xxx() will not be called until
pm_runtime_put_noidle() is called in ->probe(). And
should be done as one of the latest actions in
->probe(), after the normal probe actions succeeded.
OK, just as your description, it seems OK.
But this is really a issue as I explained in last email.
So I want to know if there are any side-effect of changing the code
in pci_pm_runtime_xxx()
if (!pci_dev->driver)
return 0;
to
if (!dev->driver)
return 0;
If you make this change, we can not put devices into low power state
(runtime suspend the device) in ->probe(). That is expected in some
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This means dev->driver is NULL ?? but pci_dev->driver is set???
Because if use pci_dev->driver can put into low power state, means
pci_dev->driver is set, but in the situation, use dev->driver will can't,
means dev->driver = null, but I have not find any case that
dev->driver = null, but pci_dev->driver != null;
Sorry I make a mistake here. The dev->driver != null in
local_pci_probe(). We use pci_dev->driver instead of dev->driver in
pci_pm_runtime_xxx() because we want device to be kept in normal power
state (D0) and SUSPENDED state when unbound.The
pm_runtime_put/get_sync in pci_device_remove/local_pci_probe will not
change the power state of the device because of the check in
pci_pm_runtime_xxx().
Yes, you are right, but what am I confuse is that, why check dev->driver
in pci_pm_runtime_xxx() can't keep the device in normal power
state (D0) and SUSPENDED state when unbound.
May be logic issue ?
Thanks
Mike
I know I always been a question guy, i apologize for spend a lot
time to reply this mail, but I really want to understand it,
Never mind.
Best Regards,
Huang Ying
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